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Tektronix 494AP User's Manual

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1. hh 4 31 dt sho nonoui 4 32 Section 6 MACROS 5 4 32 Notes on the Program Examples 6 1 PuposSssss 4 33 Math Commands iue eese nin in rero nn Eius 6 1 4 33 6 1 STORE ccisssscsscvvcssvisxereveressccacontecvesssues 4 34 e A 6 1 M 4 34 6 2 iius veess9wissnaan aate pi Xena aerea ny v 4 34 DIVIDE Ra a 6 2 PLUFTETL o n 4 35 Register Commands cscoccrccsssccsssesosrsesecnezs 6 2 P 4 35 PUTBEO a Gur RED NUN EP PDA EDU 6 2 4 36 6 3 le c IRE 4 36 6 3 MD 4 36 POPE tesis 6 3 Section 6 Section 7 Section 8 Page continued ENTEB 6 4 Branching and Looping Commands 6 4 APERTE 6 4 LAB 6 6 POR ARR 6 6 6 7 6 7 6 8 Print Commands 6 9 Bloc 6 9 6 9 icrsccocrsccsnesccncavevssesssscssesosesceses 6 10 PHINI DURO ERE 6 11 Data
2. 2 6 Compatibility Only Commands 2 6 GETTING STARTED Notes on the Program Examples 3 1 Setting and Querying Programmable Controls 3 1 Setting Programmable Controls 3 1 Querying Programmable Controls 3 3 Exercise Routines 3 3 Talk Listen 3 3 Acquiring Instrument Settings with the SET 3 4 Resetting the Programmable Spectrum Analyzer and Interface Messages 3 4 Acquiring a 3 4 Getting 3 4 Getting Smarter Another Way 3 5 INSTRUMENT CONTROL Use in 4 2 NUM Argument Values 4 2 win Yero 4 3 a c 4 4 4 4 4 4 PIAS c v c 4 5 4 5 4 5 SANNIE 4 5 MC 4 6 matis e 4 6 pi TE 4 7 MSTEP pr orn dad 4 7 xli e 4 7 7 ROO nn EEE 4 8 494AP Programmers Page Page Section 4 continued Section 4 continued 4 36 RES cscsvccevvasarivveceisvonsececksresssnunestsveases 4 8 i apo TR 4 9 Section 5 MARKER SYSTEM SETTES 4 9 Use in Macros 5 1 1 eese
3. init vesscecasi 4 20 Eo 5 9 4 21 RERO m 5 9 FPEAN 4 21 Marker Findilig nr niin arae s 5 9 MINATT vcssssvncsostencessoscveantncessoisccveasoats 4 22 HRAMPL 5 10 ipit PER 4 22 5 10 orina e prd Coni 4 23 5 10 PLS TR auia is 4 23 BWMODE 2 ore naues 5 11 VIDELT 4 23 MP BIG 5 11 SWORD DOO 4 24 MLETNI oue 6 5 11 TRIG 4 24 irri 5 12 SIGSWP Aem 4 25 ieiossisakees xinerus essesPa Kite 5 12 4 25 5 13 Digital Stored rire ieri rni 4 27 MIMIN Didot ders 5 13 AVIEW asssesssk vi nd vxeseci aas na 4 27 MRGTNA CHEER 5 13 SERM 4 28 THRELD svcicsnisseverevassvecs ssvcenvecetesensiies 5 14 PO 2 T MH P 4 28 jM nl 5 14 4 28 MVHTDB noinine ss 5 14 DSTORE ccsssecessinivisssteccusveccessovesvateoes 4 28 ORR VEHI 5 15 DRECAL 2 icisssissnssevsesscsscsevensssactoaessesvs 4 29 P 5 19 tnl a PPP et 4 29 MR RE 5 19 RHENUM UNES BT 4 29 ZOOM aec 5 19 Display CORIO ise eorr er ete 4 31 T 5 19
4. A 2 A 2 Interface Messages and Functions A 4 vii 494AP Programmers SAFETY SUMMARY Refer all servicing to qualified servicing personnel The safety information in this summary is for both operating and servicing personnel Specific warnings and cautions will be found throughout the manual where they apply but may not appear in this summary CONFORMANCE TO INDUSTRY STANDARDS This instrument complies with the following Industry Safety Standards and Regulatory Requirements Safety CSA Electrical Bulletin FM Electrical Utilization Standard Class 3820 ANSI C39 5 Safety Requirements for Electrical and Electronic Measuring and Controlling Instrumentation IEC 348 2nd edition Safety Requirements for Electronic Measuring Apparatus Regulatory Requirements VDE 0871 Class B Regulations for RFI Sup pression of High Frequency Apparatus and Instal lations TERMS In This Manual CAUTION statements identify conditions or practices that could result in damage to the equipment or other property WARNING statements identify conditions or practices that could result in personal injury or loss of life viii As Marked on Equipment CAUTION indicates a personal injury hazard not immediately accessible as one reads the marking or a hazard to property including the equipment itself DANGER indicates a personal injury hazard immedi ately accessible as one read
5. The EVENT query returns more detailed information about the event reported in the last serial poll status byte It also allows a controller to get information about events when the device s ability to assert RQS has been turned off RQS OFF Response to EVENT query Dre NR1 is an event code defined later in this section in Table 9 4 The EVENT is cleared when the event code is reported There is no EVENT command ALLEV all events query Response to ALLEV query Toore The NR1 s is the event code defined later in this sec tion in Table 9 4 Events are cleared when their event codes have been reported There is no ALLEV command ERR error query Response to ERR query ERR returns any current error codes in numerical order Reading the current code s clears the error response error codes are listed in Table 9 4 There is no ERR command ERCNT error count query ene 7 Response to ERCNT query co System Commands and Queries 494AP Programmers ERCNT returns the number of error codes to be returned for an ERR query There is no ERCNT command NUMEV number of events command NR1 This specifies that a fixed number of event codes is to be returned in ALLEV If fewer events are pending when ALLEV is executed the response is filled with zeros to provide the specified number A value of zero sets the spectrum analyzer to return a variable num
6. 4 9 NUM Argument 5 1 DEGAUS os cersrsecsrectecvecscseatssscsstesteeveies 4 10 Waveform Finding caicissenseseosenssevcessses 5 1 lato 1 4 10 System Control oorr nro 5 1 4 10 MAP 5 1 Frequency Span Resolution 4 11 entera did ERES 5 2 BEA 4 12 MIASON 5 3 4 12 7 5 4 MXOPN 4 13 aUlpz WERDE ERE EM 5 4 RESBW ooo rara nano 4 13 GOTRANK 5 5 4 14 Marker Positioning ne orato ond 5 5 17 pestem 4 14 DR Ux 5 5 Vertical Display and Reference Level 4 15 eo exist daro Rate vag 5 6 VRTDSP r 4 16 MOEN E 5 6 272750 8 71 4 16 ui 0 1 5 6 4 17 5 7 itae nob ioo 4 18 qme 5 7 4 18 ball 5 8 ENGAL ccccieccisancvenscassnssscesisnssconesesssenss 4 19 76 2 Li on na EUER 5 8 PRIN eei Fi o FERE alie 4 20 Mo 5 8
7. 7 dB 199 X 74dB 6 dB 19 5 dB 1dB X 5 mode 0 25 dB 3 dB Delta Amplitude 3 dB mode 0 25 dB mode 0 25 dB 1 dB Delta Amplitude 1 dB mode 0 25 dB LIN Either 6 dB or 8 dB varies to match 1 2 5 volts div sequence Examples REF 200DBV REFLVL 10 DBMV REF 30DBUV REFLVL 25 DBM REF INC Macro Memory Used 4 bytes Power up value 0 dBm REFLVL reference level query Instrument Control 494AP Programmers Response to REFLVL query rE ne Only the number value will be returned the units will not be indicated the number will be returned in the current reference level units The value returned is the absolute reference level whether or not in the Delta Amplitude mode RLUNIT reference level units command NOTE To ensure the correct response all of the letters in each of the unit mnemonics for the RLUNIT command must be entered not just the first three letters as required for most other mnemonics DBM The reference level REFLVL units are set to dBm DBV The reference level REFLVL units are set to dBV DBMV The reference level REFLVL units are set to dBmV DBUV The reference level REFLVL units are set to dBuV NUM 0 dBm 1 dBV 2 dBmV 3 dBuV Macro Memory Used 2 bytes Power up value dBm Interaction In instruments with Option 07 installed dBmV is automatically selected when the 75 0 i
8. 8 1 Waveform Finding eene eene 8 1 POINT neari 8 1 1 8 2 LETNIE 8 2 RG TINA T caicccsccccctseccesccscsdessvsensssssvessouese 8 2 7 rm 8 2 8 2 Section 8 Section 9 Section 10 494AP Programmers Page continued Data Point Commands Interaction 8 2 8 3 27 8 3 SYSTEM COMMANDS AND QUERIES NUM PAPO ING i iai veis 9 1 Use m MBOIOB o eco arredi 9 1 Instrument Parameters 9 1 1 9 1 9 5 JJ 9 5 HDR f 9 6 Message 9 6 WALT ode 9 7 ivre o 9 7 Status and Error Reporting 9 7 2e 9 7 R 9 8 9 8 9 9 Effect of Busy on Device Dependent Messages 9 9 Effect of Busy on Interface oorr qox Xa ie 9 9 9 10 EVEN TE scsttncescccosssscevsstieveveieverecsssseases 9 10 ALLEVI 9 11 9 11 ERGNT 9 11 Ql cl 9 11 PR DUUM A 9 11 9 12 Error ME 9 13 HELPS AND HINTS Notes on the Program Examples 10 1 Programming Techniq
9. onm DI SR Ae MSTep PES c E SS 8B Hull DST QS E v Ud rinm VE SE Dane LE Rl pe d MXSPN Ae N 4 wise A RF INPUT 502 ONEN DREcAL SAN max MINATT CAL DIScon FIRst MXHLo IMPED MTOP FINE ENCat CRSon BMiNA 5559 04A OPTION 07 ONLY A Through M REDour VRTpsp VIDFLT RECaL STORE TMObve TUNE PSTep STEP NS NS PLOT TE SSR CENTERIMARKER a 1 FREQUEN RESsw SPA NN mM REF vi VRTbsP ww ZERosp POFSET PTYPE PLSTR SEConp PEAK RGMope RLUnNit SAVEA REFivi 5559 05A RLMope N Through Z Appendix B 494AP Programmers Mnemonic ALLEV ARES AVIEW BMINA BVIEW BWMODE BWNUM CAL CENSIG CLEAR CLIP CNTCF COUNT CRES CRSO CURVE DCOPY DEGAUS DELFR DISCOR DIVIDE DONE DPMK DPRE DRECAL DSLINE DSTORE DT ECR Evarv EXCHG EXMXR FIBIG FINE FIRST QUICK REFERENCE TO COMMANDS AND QUERIES Query Available Macro Memory Used Yes Yes Yes On Off Yes On Off Yes On Off Yes Number Yes Special None Number On Off None On Off Number Special Special None None On Off On Off None None None None Special Special Special On Off On Off 2 bytes None 4 bytes None 0 bytes On Off 2 bytes None 1 byte Special 10 bytes On Off 2 byt
10. NUM is a decimal number integer floating point or scientific notation NUM may be substituted for ON or OFF 1 ON 0 OFF NUM may be followed by units in engineering nota tion for frequency time and amplitude 100 MHz 10 us 60 dBm e Be sure to keep copies of all macros so they can be more easily recreated in case the memory is inter rupted as in the case of removing the battery for long term storage e Keep an accurate account of the memory used in each macro use the MEMORY query to find out how much memory a particular macro uses or to find out how much memory is left for additional macros e Queries are acted upon as soon as they are received and cannot be used in macros e Once a macro is entered into memory it cannot be changed The macro must be removed by number KILL NUM and completely re entered Appendix B 494AP Programmers PROGRAMMING SUMMARY AYVININS ONINWWVHOOHd STATUS BYTE OOOOOOO O Decimal _ onim 65 81 Power on 2 18 66 82 End of Sweep 0 16 Ordinary operation 33 49 97 113 Command error 34 50 98 114 Execution error 35 51 99 115 Internal error 37 53 101 117 Execution error warning 38 54 102 118 Internal error warning lt x lt x KK KO RK HIN X X X X X x x mum o000000 o oo oo00col tm O Oo O O 0 0 0 0 0 0 0 0 Four bit status code STSTOP STEP Spectrum analyzer busy condition Ab
11. e 4 22 MAXPWR maximum input power command R SP NUM This is an input to a instrument that protects the RF INPUT from overload at the expected maximum power level The instrument selects a minimum RF attenuation so that the NUM signal level is reduced to no more than 18 dBm at the 1st Mixer This is the instrument s 1 dB compression point The maximum non destructive power level that can be connected to the RF INPUT is 30 dBm If no units are specified the instrument assumes the current reference level units If the number selected is out of range execution error message 33 is issued NOTE To ensure the correct response all of the letters in each of the units mnemonics for the MAXPWR command must be entered not just the first three letters as required for other mnemonics INC or DEC The minimum RF attenuation is changed to the next higher or lower step if any Macro Memory Used 4 bytes Examples MAXPWR 20DBMV MAX 18 DBUV MAXPWR DEC Power up value 18 to 42 dependent on MINATT value 18 MINATT value Interaction The range of RF attenuation is limited in response to the MAXPWR command which limits the range of the REFLVL command MAXPWR cancels the previous limit set by either MINATT or MAXPWR MAXPWR maximum input power query Response to MAXPWR query MAXPWR SP Only the number value will be returned the units will
12. 8 SH and Source and Acceptor Handshake Functions A 9 DC Device Clear Function A 9 DT Device Trigger Function A 9 C SR and PP Controller Service Request and Parallel Poll Furteolll 10 Taking Control Asynchronous or SynchrOnOUS A 10 10 Performing a Serial Poll A 10 Performing a Parallel Poll A 10 PROGRAMMING FUNCTIONS Programming Summary Notes Status Byte Interface Messages Commands and Queries Quick Reference to Commands and Queries Sample Macros Macro Preparation Pass Fail Harmonic Test Macros Continued Harmonic Macro Test Output For the Harmonic Macro Test Front Panel Relationship to Mnemonics ERR ERCNT Responses ERR Responses Numerical Order 494AP Programmers LIST OF ILLUSTRATIONS Figure Figure Number Page Number Page TEKTRONIX 494AP Programmable 5 1 Using the PKFIND command 5 12 Spectrum X 9 2 Locating the signal 5 15 1 1 GPIB pushbutton and indicators 1 1 5 3 Signal finding 5 16 1 2 Status of active GPIB functions 1 2 5 4 Signal finding 5 17 1
13. Bwnum gt P CIDRO CON aR CO none Ramone INIT initialize settings command INIT resets the instrument the same as if the power was turned off then turned back on The instrument functions are reset as shown in Table 9 1 Macro Memory Used 1 byte interaction IEEE 488 interface functions are not affected and the instrument remains under remote con trol RQS is set to OFF if either the LISTEN ONLY or TALK ONLY switch is set There is no INIT query OC OSH System Commands and Queries 494AP Programmers ID identify query Response to ID query Cmm C Da DO 494AP The instrument type number V lt NR2 gt Tektronix Interface Standard for GPIB Codes Formats Conventions and Features version number System Commands and Queries 494AP Programmers FV lt NR2 gt Instrument firmware version number FPV NR2 Front panel processor firmware ver sion number There is no ID command Table 9 1 INSTRUMENT FUNCTIONS Mnemonic FREQ FIRST SECOND DISCOR FRQRNG DELFR SPAN ZEROSP ARES MXSPN PHSLK VIDFLT VRTDSP REFLVL FINE RLMODE MINATT PLSTR TRIG SIGSWP TIME AVIEW BVIEW SAVEA BMINA MXHLD CRSOR REDOUT GRAT PT OFF YOFF CLIP TEXT EOS RQS WARMSG NUMEV IMPED RLUNIT STSTOP HDR SGERR SGTRAK MCPOIN NSELVL TMODE STYPE MTRACE PRIMAR MTRACE SECOND THRHLD 9 6 INIT Value 9 0 2 972 9 2 182 OF
14. 10 12 increase and decrease the marker frequency The MMAX and MMIN command arguments will still be frequency values Thus there will be no way to limit a marker max imum or minimum search to a specific horizontal range in zero span The MCEN and PKCEN commands are not available zero span Both BWMODE and SGTRAK wil be IDLE while ZEROSP is on USING MULTIBAND SWEEP It is possible to sweep a frequency range that covers more than one band as long as the entire frequency range is within the range of the preselector 1 7 GHz 21 GHz The low pass filter preselector boundary may not be crossed when using the internal mixer as this would lead to excessive wear of the preselector switch The multiband function is also available if the external mixer is in use however if the external mixer is being used the range that can be swept is 10 KHz 21 GHz In the waveguide bands the sweep range is restricted to a single band since each band normally requires a different mixer Entering the Multiband Sweep Mode Enter the Multiband Sweep mode with the STSTOP command over the GPIB or by recalling a setting using multiband sweep with the RECAL command Multiband sweep is started automatically when STSTOP is used to enter a sweep that covers more than one band within the allowed multiband range Send the STSTOP command with the desired start frequency and followed by the stop frequency Multiband Sweep Operation To sweep a rang
15. 2 bytes There is no MENU query SWEEP take a sweep command 6 16 The SWEEP command will start a new sweep and wait until the sweep has finished before executing the next macro command Macro Memory Used 1 byte There is no SWEEP query VAR variable query Response to VAR query moe The VAR query response will return the value of vari able NUM If NUM is out of range 0 is returned no error message is issued Range 1 to 30 There is no VAR command STMAC store macro command P The STMAC command tells the spectrum analyzer that the following GPIB commands will be stored as macro number NUM with a title of the CHARACTER string The spectrum analyzer will continue to store all commands until it receives the EMAC end macro com mand which tells it that entry for macro NUM is done Any query lines given between STMAC and EMAC will be executed as they are read and will not be saved as part of the macro The title CHARACTER string may be up to 22 characters Example STMAC 1 HARMONIC TEST Range NUM is O to 7 Interaction If the STMAC command is given and a macro is running or stopped then that macro is aborted If a macro is being entered and an illegal command is entered macro entry is aborted and the instrument is put back in the regular operation mode There is no STMAC query GETWFM get waveform command The GET
16. 494AP Programmers This causes the spectrum analyzer to output 12 fre quency values because it only performs the frequency query once on its second pass through the entire mes sage The REPEAT command cannot be used within a macro Interaction A REPEAT loop can only be stopped by DCL Pressing RESET TO LOCAL does not stop the loop it only causes execution error messages to be reported if the loop contains front panel commands If RESET TO LOCAL is pressed while a message that includes REPEAT is being acted on the message will only be repeated 256 times Since most commands are ignored after the RESET TO LOCAL button is pressed the REPEAT loop completes quickly There is no REPEAT query STATUS AND ERROR REPORTING Two commands EOS and RQS control spectrum analyzer service requests STATUS BYTE reports instru ment status in a format that includes both IEEE 488 and the Tektronix Interface Standard for GPIB Codes For mats Conventions and Features GET is enabled to trigger a new sweep DT two queries ERR ERCNT return the error codes a query EVENT returns detailed information about events reported in the last serial poll status byte two queries and one command ALLEV NUMEV EVQTY specify the identity and quantity of events reported EOS end of sweep command ON The spectrum analyzer asserts SRQ if RQS is ON when a sweep completes OFF The spectrum analyzer does not assert SRQ for
17. FPSET The front panel settings contained in the indicated register are transferred DISP The waveform and the associated readout and scaling data contained in the associated register are transferred NUM The number of the storage register to which data will be transferred The number must be in the range of 0 9 when FPSET is used or the range 0 8 when DISP is used RDATA response BINARY BLOCK The length of the binary data exclusive of the byte count and checksum see Binary Block in Section 2 of this manual is 128 bytes when a setting is being returned and 642 bytes when a display is being returned If the register number sent with the query is out of range a register number of 1 will be returned If the requested register did not contain valid data a register number of 2 will be returned In either of these cases all binary data bytes will be O PLOT query 9 7 The PLOT query sends information to plot the display on a TEKTRONIX 4662 Opt 01 4662 Opt 31 or 4663 emulating a 4662 Interactive Digital Plotter a Hewlett Packard HP7470A HP7475A HP7580B HP7585B or HP7586B plotter or a Gould 6310 or 6320 plotter e if REDOUT is ON corresponding settings will be plotted If GRAT is ON the scale down the right hand side of the screen will be plotted as well as the graticule information If REDOUT is also ON the bezel infor mation will also be plotted this assumes that the no
18. Otherwise The center frequency is put into the step size if delta markers are off and the Tune CF Mode is on There is no MSTEP query PSTEP plus step command 4 7 Instrument Control 494AP Programmers The PSTEP command increases the center fre quency if you are in the tune frequency mode by the value set in the STEP command if possible If you are in the tune marker mode the primary marker frequency is increased If the step marker is on a saved trace and you go outside the displayed trace execution error message 120 will be issued Macro Memory Used 1 byte Power up value See Interaction that follows Interaction If the frequency or delta to which the step size is to be set is larger than 155 GHz the step size will be set to 155 GHz If STEP has not been set PSTEP will set STEP to the following values e The absolute value of the delta frequency is put into step size if delta markers are on e The marker frequency is put into the step size if delta markers are off and the Tune Marker Mode is on Otherwise The center frequency is put into the step size if delta markers are off and the Tune CF Mode is on There is no PSTEP query COUNT counter command ON The counter mode is turned on OFF The counter mode is turned off When no argument is included an immediate signal count occurs whether or not the counter mode is on no change occurs in the ON OFF status of the
19. RESBW out of range 33 MAXPWR or MINATT out of range 34 Level out of range REFLVL THRHLD BWNUM MVRTDB MVLFDB 35 VRTDSP LIN out of range 36 VRTDSP LOG out of range 37 TIME out of range 39 IDENTify not allowed in this span div 40 Signal finds not allowed in zero span 41 Invalid DATA or ADDR argument contents 42 DATA direction not compatible with ADDR direction 45 GET Group Execute Trigger ignored not executed 46 NUMEV out of range 47 STORE RECALL DSTORE DRECAL or RDATA out of range 48 PHSLK cannot be turned OFF ON directly with PHSLK command 101 Function not available when SGTRAK is on 102 Frequency range limited in 75 input Option 07 only 103 Frequency out of range after step 104 Bandwidth mode is not available when in linear 105 Illegal sweep range 106 Argument out of range 109 ROFSET out of range Execution Warnings 49 550 FREQ change caused change 50 551 SPAN defaulted to MAX 52 553 UNCAL light turned on 53 555 Multiple use of display buffer If this error message is issued the macro in progress will be aborted ERR RESPONSES In Numerical Order For Quick Reference Code Meaning 0 No error Illegal numeric format 4 END received in block binary 5 Block binary checksum error 6 Illegal placement of question mark 7 Query not recognized 8 Header not recognized 9 End of message unit not expected arguments missing 10 Character argument not allowed 11 Numeric argument not all
20. Send the command header to the instru ment The terminating semi colon stops the 4041 from asserting EOI so the header and the data that follows will be received by the spectrum analyzer as a single message Line 150 Send the settings data to the instrument The image specifier 4 896 selects binary block format and sends the right most 8 bits of each element of w to the spectrum analyzer The percent sign and byte count preceding the data and the checksum following the data are sent automatically by the 4041 SCALING SAVING AND GRAPHING WAVEFORM DATA The spectrum analyzer waveform data outputs numbers from 0 to 255 called screen units These numbers can be scaled to electrical units using data con tained in the WFMPRE response Here is an expanded version of the spectrum analyzer binary output program given above This version transfers whatever portion of memory you have previ ously specified with a WFMPRE command A B or FULL power up default is FULL The program scales both the X and Y values and stores them in a two wide array The program also saves the non scaled binary array so you can transfer it back into spectrum analyzer digital storage if you wish This example cannot be used in customized macros as presented here because it con tains the CURVE and WFMPRE commands 100 GET AND SCALE SPECTRUM ANALYZER BINARY CURVE OUTPUT 110 Delete var w m 120 Print 1 WFMPRE 130 Input dein 1 n x3
21. Setting the LF OR EOI Switch Switch 3 of the rear panel GPIB ADDRESS switch bank see Figure 1 3OQ selects the terminator for mes sages on the bus If LF OR EOI is selected switch up 1 the spectrum analyzer interprets either the data byte LF or the end message EOI asserted concurrently with a data byte as the end of a message If EOI is selected switch down 0 the spectrum analyzer interprets the end message EOI asserted as well as a data byte as the end of a message Introduction to GPIB Operation 494AP Programmers Table 1 1 BUS ADDRESSES Primary Listen Talk Address Address Address 168421 00000 0 64 00001 1 65 00010 2 66 00011 3 67 00100 4 68 00101 5 69 00110 6 70 00111 7 71 01000 8 72 01001 9 73 01010 10 74 01011 11 75 01100 12 76 01101 13 77 01110 14 78 01111 15 79 10000 16 80 10001 TT 81 10010 18 82 1001 1 19 83 10100 20 84 10101 21 85 10110 22 86 10111 23 87 11000 24 88 11001 25 89 11010 26 90 11011 27 91 11100 28 92 11101 29 93 11110 30 94 11111 31 UNT Switch 3 also selects the output terminator Set to LF OR EOI the instrument adds CR and LF with EOI asserted as well as LF after the last byte of the mes sage Set to EOI the instrument asserts EOI con currently with the last byte of the message Figure 1 4 shows the effect of this switch for both input and output Select EOI switch down for Tektronix controllers The other position of this switch is provided to acc
22. stant should be larger for wide bandwidths than for nar row bandwidths Alternatively the positive peak noise level can be found directly with FMAX or MMAX if all signals are tuned off the screen The value of THRHLD can also be set to AUTO The threshold used for marker related signal processing commands will then be set slightly above the expected noise level as determined by the instrument s sensitivity specification attenuator setting resolution bandwidth and video filter bandwidth The actual threshold value chosen will be returned in the response to the THRHLD query Acquiring Data for Waveform Processing Both the signal separation and the noise considera tions mentioned previously need to be addressed when the waveform is acquired as well as when the signal processing commands are actually used Signal separation can be improved by selecting a narrower resolution with the RESBW command This may require the sweep to be slowed to maintain amplitude and frequency calibration TIME AUTO will automatically maintain a calibrated display if possible Noise peaks can be reduced by smoothing the data as it is acquired by means of video filters and or digital averaging The bandwidths of the wide VIDFLT WIDE and narrow VIDFLT NARROW video filters are automati cally changed in step with the resolution bandwidth To use digital averaging select CRSOR AVG or set the peak average line above the noise floor and select
23. 180 Print z ENTER MFREQ STNUM 3 190 Print z PRINT 4 1 XREG FFORMT 18 0 200 Print z ENTER MAMPL STNUM 2 210 Print z PRINT 4 28 XREG DEC 6 1 220 Print z PRINT 5 1 230 Print z PRINT 6 1 HARM LEVEL DBC 240 Print z STEP MARKER 250 Print z FOR 1 1 10 260 Print z ENTER 6 ENTER VAR 1 PLUS STNUM 5 270 Print z PRINT VAR 5 2 VAR 1 DEC 2 0 280 Print z PSTEP SWEEP MFBIG 290 Print z IF SIGNAL 300 Print 4Xz ENTER MAMPL 310 Print z PRINT VAR 5 15 XREG DEC 6 1 DBM 320 Print z ENTER VAR 2 330 Print z SUBT 340 Print z PRINT VAR 5 33 XREG DEC 6 1 350 Print z ELSE 360 Print Xz PRINT VAR 5 6 NO SIGNAL 370 Print z ENDI 380 Print z NEXT 390 Print Zz TEXT MACRO 400 Print z FREQ VAR 3 410 Print z ELSE 420 Print z PRINT 4 2 NO SIGNAL FOUND 430 Print z PRINT 6 10 MACRO KILLED 440 Print z ENDI 450 Print z DONE 460 Print z EMAC Appendix B 494AP Programmers HARMONIC TEST MACRO Continued Line 100 Store the following macro in menu position 1 and title it HARMONIC TEST Line 110 Turn on a single marker Line 120 Turn on the normal readout and clear the macro readout buffer Line 130 Print HARMONIC TEST on line 1 beginning 1 space from the left Line 140 Take a sweep then move the marker to the signal peak Line 150 Do a harmonic test Line 160 Center the marker Line 170 Print the fundamental frequency and amplitude on line 3 beginning 1 s
24. For additional information refer to the descriptions of PKFIND and MCEN earlier in this section Macro Memory Used 1 byte Interaction PKCEN is not available in ZEROSP or MXSPN There is no PKCEN query MMAX move marker to maximum command The MMAX command sets the Primary marker to the largest vertical value in digital storage If the largest value is located at more than one point the first left most point is used NUM NUM The optional arguments are two fre quency values If these are present the search is limited to the intersection of the given frequency range and the range displayed on the screen If the given range is totally outside the range displayed on the screen execu tion error message 28 is issued Macro Memory Used 12 bytes Examples MMAX 15 0MHZ 19 0MHZ MMA 15 0MHZ 19 0MHZ Interaction If MARKER is OFF MMAX sets MARKER to SINGLE There is no MMAX query MMIN move marker to minimum command Marker System 494AP Programmers The MMIN command sets the Primary marker to the smallest vertical value in digital storage If the smallest value is located at more than one point the first left most point is used NUM NUM The optional arguments are two fre quency values If these are present the search is limited to the intersection of the given frequency range and the range displayed on the screen If the given range is totally outside the range
25. GET SPECTRUM ANALYZER CURVE OUTPUT 510 Integer w 1000 Declare integer array 520 Print z WFMPRE ENC BIN 530 Input prompt CURVE using FA 896 dels z header w 540 Waveform heading is in header data in w array Line 510 Declares an integer array large enough for a full 1000 points Line 520 Requests the spectrum analyzer to for mat data in a binary format Line 530 Uses the input prompt to request a curve The free field input for the header string is delim ited from the data a comma with the dels clause and enters the array w in an 8 bit word format with the image specifier 8 The byte count words and checksum are input and checked automatically Checksum failure results in a trapable error interrupt to the 4041 Sending a Binary CURVE to the Spectrum Analyzer The following routine employs end block format to transfer a waveform to the spectrum analyzer Array w is transferred if not already created by the preceding rou tine w should be dimensioned to 1000 and filled with data in the range 0 to 255 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 600 TRANSMIT A BINARY CURVE TO THE SPECTRUM ANALYZER 610 Print using 8 z w Line 610 Sends the image specifier 8 followed by the binary numbers in array w after which it asserts EOI causes the spectrum analyzer to act on the message The CURVE header is omitted it is not required but would be accepted if sent The spectrum analyzer b
26. If the TEST query response is TEST ROM 4112 RAM 18 then ROM 1 The binary equivalent of the ROM number 4112 is 00100000001 000 2 Insert this binary number in part A of Figure 9 1 right justified Blocks 6 and 2 will be Off This indicates that both ROM 6 and ROM 2 are bad all other ROMs are good 3 Table 9 3 shows that ROM 6 is U1025 and that ROM 2 is U1010 both located on the GPIB board RAM 1 The binary equivalent of the RAM number 10 is 1010 2 Insert this binary number in part B of Figure 9 1 right justified Blocks 4 and 2 each contain a 1 which indicates that both RAMs 4 and 2 are bad all other RAMs are good 3 Table 9 3 shows that RAM 4 is U1020 and RAM 2 is U3020 both located on the Memory board There is no TEST command Table 9 3 TEST CONVERSION Chart Circuit Location Board A54 Memory A54 Memory A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A56 GPIB A54 Memory A54 Memo A54 Memory A54 Memory A54 Memory A54 Memo Device 4050 O0n o0 Circuit Number U3060 U1010 U1010 U1020 U1020 U1025 U1025 U1035 U1035 U3015 U3015 U3020 U3020 U3030 U3030 U3020 System Commands and Queries 494AP Programmers 9 8 7 6 5 3 2 1 0 00 INSTALLED 01 INSTALLED BAD 10 NOT INSTALLED ROM DATA STORAGE RAM SYSTEM RAM 5564 14
27. OFF lt 0 5 are rounded to 0 WAVEFORM FINDING The spectrum analyzer has two sets of waveform finding commands five commands are described in this section and two are described in Section 8 of this manual The MRGTNX and MLFTNX marker positioning commands move the Primary marker and RGTNXT and LFTNXT waveform processing commands move the invisible display data point The Primary marker is specified and reported in frequency and amplitude and the display data point is specified and reported in screen units The two locations marker and data point and the two sets of commands are independent unless the Pri mary marker and the display data point are coupled with the MCPOIN command The DPMK command moves the display data point to the Primary marker location without coupling the two and MKDP moves the Primary marker to the horizontal location of the display data point also without coupling the locations SYSTEM CONTROL The system control commands turn on the marker mode MARKER set the Primary or Secondary marker on a trace MTRACE assign a marker function to the front panel ASSIGN 1 or ASSIGN 2 pushbutton M1ASGN or M2ASGN normalize the Primary marker amplitude readout to the resolution bandwidth NSELVL and keep the Primary marker signal at center screen SGTRAK MARKER marker mode command OFF The marker is turned off ON or SINGLE The single marker is turned on DELTA The delta marker is tu
28. ON The instrument settings are displayed 3 Corr OFF The instrument settings are not displayed the readout is blanked Macro Memory Used 2 bytes 4 31 Instrument Control 494AP Programmers GRAT graticule command ON The crt graticule is lighted OFF The crt graticule is dark not lighted Macro Memory Used 2 bytes Power up value OFF GRAT graticule query Response to GRAT query CLIP blank baseline command ON Aproximately one graticule division of the screen trace is turned off at the baseline of the crt This allows the readout at the bottom of the screen to be clearly seen when viewing or plotting the display and it eliminates the bright baseline when photographing the display OFF The full trace is displayed on the crt Macro Memory Used 2 bytes Power up value OFF CLIP blank baseline query gt Response to query CD POTD Instrument Control 494AP Programmers GENERAL PURPOSE The general purpose commands and queries request front panel help messages or GPIB command headers HELP store settings in memory STORE recall settings from memory RECALL transfer data to and from storage memory RDATA plot crt information PLOT on a choice of plotters PTYPE change B A reference for the plotter POFSET cause oscillator corrections at the end of every sweep ECR send a service reque
29. Response to BWNUM query BWMODE marker bandwidth mode command The BWMODE command moves the delta markers down from the peak of the signal that the Primary marker is on by the value set in BWNUM This value could also have been set from the front panel If no value has ever been set the value used will be 6 dB BWMODE moves in 1 10 dB steps The Primary marker is placed on the right higher frequency side of the signal and the Secon dary marker is placed on the left lower frequency side of the signal If the Primary marker is not on a signal or if a point NUM dB set by the BWNUM command down cannot be found on each side of the signal the Secon dary marker moves to the location of the Primary marker and BWMODE goes to IDLE When BWMODE goes to IDLE marker execution warning message 130 is issued if SIGERR is on Macro Memory Used 2 bytes Power up value OFF Interaction BWMODE sets MARKER to DELTA The markers are reset after the marker position or BWNUM is changed or at every sweep if on an active trace The definition of the criteria for a signal is set by the THRHLD command The Lin Mode Multiband Sweep Mode and Zero Span Mode are not available in BWMODE BWMODE marker bandwidth mode query BWMODE Response BWMODE query MFBIG marker peak find command The MFBIG command moves the Primary marker to the peak of the largest on screen signal If no signal peak is found the mar
30. Section 7 494AP Programmers DISPLAY DATA AND CRT READOUT The spectrum analyzer follows the Tektronix Inter face Standard for GPIB Codes Formats Conventions and Features for waveform transfer The commands and queries in this section transfer display and readout data to or from the spectrum analyzer and are divided into two categories waveform transfers and crt readout transfers Use in Macros Most of the 1 0 commands in this section can be incorporated into macros designed to your specific needs No queries can be used within macros Since there is a total of 8k bytes of memory dedicated for macro use it is important that you know the number of bytes used for each command and keep this in mind while preparing macros This maximum number of bytes used is included with the commands in this section and there is also a table in the Index at the back of this manual that lists all available spectrum analyzer com mands and the bytes used by each WAVEFORM TRANSFERS The waveform transfers begin with a waveform preamble WFMPRE that identifies and scales the data and continue with data CURVE that represents the waveform A query WAVFRM displays the responses to the WFMPRE and CURVE queries The display pream ble DPRE contains the numeric data necessary to reproduce the display The display units necessary to make a hard copy of the display DCOPY can be transmitted to another unit A readout command RDOUT
31. THRHLD moves in 1 dB steps AUTO The threshold is set to approximately the sensitivity specification plus RF attenuation plus the video filter offset The video filter offset is 10 dB if there is no filter 4 dB if WIDE is ON and 2 dB if NARROW is ON NUM The threshold is set to level input If no units are specified the spectrum analyzer assumes the current reference level units Macro Memory Used 4 bytes Examples THRHLD AUTO THRHLD 40DBMV Power up value AUTO THRHLD marker threshold query Response to THRHLD query rore 5 14 MVLFDB move marker left x dB command The MVLFDB command moves the Primary marker to the left and NUM DB down negative NUM or up posi tive NUM or NUM without a sign from the current posi tion If the requested amplitude cannot be found the marker does not move Macro Memory Used 3 bytes Interaction If MARKER is OFF MVLFDB sets MARKER to SINGLE If SGERR is ON marker execution warning message 130 is issued if the requested ampli tude is not found MVLFDB move marker left x dB query Response to MVLFDB query FOUND is returned if the last MVLFDB command moved the marker to the requested position FAILED is returned if the last MVLFDB command could not move the marker to the requested position If the MVLFDB query is given before any MVLFDB command FAILED is returned MVRTDB move marker right x dB command The MV
32. The instrument 2ND LO is set to the requested frequency The resulting center frequency will be displayed Macro Memory Used 6 bytes Example SECOND 2182 MHZ Instrument Control 494AP Programmers Range Bands 1 and 5 12 is 2181 2183 MHz Bands 2 4 is 718 720 MHz Range Refer to Table 4 2 Power up value 2182 MHz SECOND 2nd LO frequency query Response to SECOND query Cana a SECOND SP TGMODE tracking generator mode command The TGMODE command allows higher frequency accuracy when using a tracking generator When TGMODE is ON the frequency correction factors for all resolution bandwidth filters wider than 10 kHz are dis abled These wide filters may be centered too far from 10 MHz for the difference to be corrected with the Track ing Adjust control on the tracking generator ON The tracking generator mode is turned on OFF The tracking generator mode is turned off Macro Memory Used 2 bytes Power up Value OFF TGMODE tracking generator mode query TGMopE 5 Response to TGMODE query SAMODE sideband analyzer mode command D m O LU Instrument Control 494AP Programmers SAMODE is active in Band 1 only When the SAMODE command is ON the spectrum analyzer phase locks in 50 kHz div instead of the normal 200 kHz div This extends the usefulness of the 1405 Sideband Analyzer which uses only the first local oscillator
33. The ranges of the FREQ and TUNE commands differ in several respects The range of the FREQ command covers the entire range of the instrument The TUNE command is limited to the current frequency range 10 11 Helps and Hints 494AP Programmers USING THE TIME MEASUREMENT FEATURE This instrument employs a special time measurement feature that is available whenever the instrument is in the zero span mode of operation or ZEROSP or ZETIME are on The marker frequency readout or delta marker fre quency readout is replaced by a time or delta time readout respectively The time readout in the single marker mode is the time to the marker position from the trigger point this point is 1 2 division to the left of the screen In the delta marker mode the delta time readout gives the time difference between the two markers In both cases the time value is scaled from the marker position s and the time division No actual time meas urement is done The time measurement feature is available only dur ing certain timing conditions If the TIME command is set to MAN EXT or a setting faster than 1 ms division a value of 200 will be returned by the MKTIME query When the MARKER command is DELTA both mark ers must be on the same trace for time measurement If the markers are on different traces when ZEROSP is turned on the secondary marker will move to the trace of the primary marker This marker will not move back when ZEROSP is tur
34. The spectrum analyzer does not handshake out the data in line 140 until it finishes executing the mes sage in line 130 Figure 10 1 further illustrates the two program con cept one in the controller and one in the spectrum analyzer and how they are synchronized with the sweep for data acquisition This figure charts the execution of the two programs arrows between the programs relate how one waits for the other The WAIT command is exe cuted in the loop that tests for the end of sweep this synchronizes data acquisition with the sweep Using the End of Sweep SRQ Although the previous method for synchronizing controller spectrum analyzer execution with the sweep is recommended there is another method This alternative Helps and Hints 494AP Programmers CONTROLLER EXECUTION SPECTRUM ANALYZER SA EXECUTION SEND FREQ I GHz SIGSWP WAIT FMAX POINT TO SA BUFFER MESSAGE TERMINATOR SET FREQ THEN START SWEEP ADDRESS SA TO TALK amp WAIT FOR SA OUTPUT FIND MAXIMUM VALUE AND BUFFER QUERY RESPONSE OUTPUT QUERY RESPONSE INPUT SA QUERY RESPONSE 5564 12 Figure 10 1 Synchronizing controller and spectrum analyzer for data acquisition 10 3 Helps and Hints 494AP Programmers may be necessary for some operating systems or appli cation programs that allow a short response time when the spectrum analyzer is made a talker or that must take
35. and SDC selected device clear interface mes sages by resetting its input and output buffers to restart bus communications When these messages are exe cuted they clear outstanding SRQ conditions and set the ERR query response to zero Power up status if selected internally is an exception see STATUS BYTE in Section 9 of this manual for more on power up status and for the affect of busy status on the execution of DCL and SDC Device Trigger DT1 The spectrum analyzer DT device trigger function allows the GET group execute trigger message to cause the instrument to stop the current sweep and rearm for the new sweep The new sweep begins when the triggering conditions are met The DT command must be on and the instrument must be in the Remote mode for GET to have any effect Controller CO The spectrum analyzer does not act as a controller CONNECTING TO A SYSTEM The spectrum analyzer can be connected directly to a GPIB system with the cable available as an optional accessory contact your local Tektronix Field Office or representative for ordering information The IEEE STD 488 PORT is shown in Figure 1 5 Printed under the IEEE STD 488 PORT are the Interface Function abbreviations and the codes indicating their use in the instrument refer to IEEE 488 Functions earlier in this section for an expla nation of each function The E2 following the functions indicates that three state drivers are used rather than open colle
36. his applies to amplitude calibration only 3 A calibration value for this item has been found but the most recent calibration attempt failed the last previously good value is used The value recorded for this item is the limit value i e the best it could do The actual required correction would exceed the limit 2 4 dB so this item is not calibrated This applies to amplitude calibration only 4 The last calibration attempt for this item succeeded 5 This filter is the reference for level calibra tion This applies to amplitude calibration only ENCAL enable calibration factors command Instrument Control 494AP Programmers OFF The filter s amplitude and frequency are not corrected and the nominal noise bandwidth is used ON The calibration factors are used internally to correct frequency and level errors and noise bandwidth in the filters ZERO Set calibration factors to 0 this does not affect OFF ON status NUM 0 OFF 1 ON 2 ZERO Macro Memory Used 2 bytes Power up Value ON ENCAL enable calibration factors query Response to ENCAL query COSO FINE fine reference level steps command ON Small steps are selected for the INC or DEC arguments in the reference level command see REFLVL for details With vertical scale factors of 1 2 3 and 4 dB div FINE ON selects the delta amplitude mode Delta Amplitude Mode The Delta
37. 0 5sto3s 624 ms 0 5sto3s 35 s 10 6 s O 10 ms div 190 ms 380 ms 80 ms 500 ms 560 ms 400 ms signal separation in div 7 3 560 ms Appendix A 494AP Programmers IEEE STD 488 GPIB SYSTEM CONCEPTS The General Purpose Interface Bus GPIB is a digital control bus that allows efficient communications between self contained instruments or devices interconnected in an instrumentation system The GPIB is an interface sys tem independent of the stimulus or measurement func tions incorporated in any instrument Instruments or devices designed to operate on the digital contro bus must be developed according to the specifications contained in IEEE Std 488 1978 IEEE Standard Digital Interface for Programmable Instrumen tation At Tektronix the IEEE 488 digital interface is commonly known as the General Purpose Interface Bus GPIB This section discusses the basic concepts of the GPIB For complete specifications refer to the IEEE Std 488 1978 standard published by the Institute of Electri cal and Electronics Engineers Inc The GPIB has four elements mechanical electrical functional and operational Of these four only the last is device dependent Operational elements state the way in which each instrument reacts to a signal on the bus MECHANICAL ELEMENTS The IEEE Std 488 defines the GPIB connector and cable assembly as the mechanical elements of the instru mentation system Standardizing the co
38. 13 Macros 494AP Programmers macro execution MCSTOP tell how much memory is used for a macro or how much is left in the spectrum analyzer MEMORY store the X register value into a variable STNUM display the requested menu MENU start a new sweep and wait for sweep to end SWEEP return the value of a variable VAR tell instrument to store the following commands STMAC get the current waveform GETWFM and input a number from the DATA ENTRY pushbuttons INPNUM PAUSE macro pause command SP NUM The PAUSE command pauses the current macro for 1 second or NUM seconds if NUM is used Macro Memory Used 1 byte There is no PAUSE query RUN run macro command SP 5 NUM The macro number NUM will be run Any macro currently running will be aborted and macro NUM will be started If any GPIB command comes while a macro is exe cuting the macro is stopped and RUN will restart it RUN without an argument will restart a stopped macro If a macro is not stopped and RUN is sent without an argument or NUM is greater than 7 macro execution error message 162 COMMAND 1 ONLY AVAILABLE WHEN A MACRO IS STOPPED is issued If RUN is sent with NUM 0 7 where no macro is located macro execution error message 165 is issued Here are two short examples of illegal RUN argu ments e RUN 10 is sent Since macro locations are 0 through 7 10 is an illegal macro
39. 2 bytes Number 2 bytes Special 12 byte Special 2 bytes None 1 byte None 1 byte None Special On Off Special Special Special None Special Number N A 2 bytes 2 bytes 4 bytes 5 bytes 2 bytes 1 byte 2 bytes 6 bytes N A None Yes Special Yes Special Yes None No On Off Yes None Yes Special Yes On Off Yes 2 bytes On Off Yes 2 bytes Number No 2 bytes Arguments are divided into the following four categories None No arguments are required On Off The arguments ON or num 1 or OFF or num 2 are required Number Number s argument required terminator optional Special Specific command arguments character strings or any combination of these categories are required This command cannot be used within a macro This command can only be used within a macro it cannot be used outside a macro HARMONIC TEST MACRO MACRO PREPARATION The folowing program shows the 4041 Data statements necessary for the HARMONIC TEST program This macro will use less than 10 of the total available 8K bytes of memory set aside for macro storage 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Print z STMAC 1 HARMONIC TEST 110 Print z MARKER SINGLE 120 Print z RDOUT NORMAL CLEAR 130 Print z PRINT 1 1 HARMONIC TEST 140 Print z SWEEP MFBIG 150 Print z IF SIGNAL 160 Print 2 MCEN 170 Print z PRINT 3 1 FUNDAMENTAL FREQUENCY AMPLITUDE
40. 3 Rear panel GPIB ADDRESS switches 1 3 5 5 Signal finding 5 17 1 4 Effect of message terminator switch for 5 6 Signal finding 5 18 CURD ERR 1 4 5 7 Signal finding 5 18 1 5 The rear panel IEEE STD 488 PORT GPIB 1 6 1 6 The spectrum analyzer can be connected to a 6 1 INPNUM 6 18 GPIB system in either a star or a linear PROM 1 6 7 1 Waveform data related to the display 7 5 4 1 Front panel Frequency commands 4 3 9 1 Test conversion 9 13 4 2 Front panel Frequency Span and Resolution vas 4 11 10 1 Synchronizing controller and spectrum 4 3 Front panel Vertical Display and Reference analyzer for data acquisition 10 3 Fol COMMANdE cccccsacessenseusequcctssxevesnnssestesisuune 4 15 10 2 How multiple use of the display data buffer 4 4 Front panel Sweep Control commands 4 24 COMMPONG oc ccsantesscessveatevcsscisd evecssvesssnesivesevens 10 7 4 5 Front panel Digital Storage commands 4 27 4 6 Front panel Display Control commands 4 31 A 1 IEEE Std
41. 37 55 47 71 57 87 67 103 77 119 10 30 SPE 50 8 70 241110 8 130 24 150 8 170 24 BS 8 H X h x 8 8 18 24 28 40 38 56 9 48 72 58 88 68 104 78 120 11 TCT 71 258111 9 131 25 5 9 171 25 HT 9 I Y i y 9 9 39 57 949 73 59 898 69 105 79 121 32 72 260112 10 132 268 152 10 172 26 SUB J Z j 2 1 26 58 B 4A 74 5A 90 6A 106 7A 122 13 33 53 11 73 271113 11 133 271 153 11 173 27 ESC K k B 11 1B 27 2B 43 3B 59 B 4B 75 5B 91 9 68 107 7 123 14 34 54 12 74 288 114 12 134 288 154 12 174 28 FF FS lt L N C 12 1C 28 B 2C 44 3C 60 8 4C 76 5C 928 6C 108 7C 124 35 75 29 115 13 155 13 175 29 6 M 1D 29 30 61 940 77 60 109 7D 125 36 76 30 116 14 136 30 156 14 176 a 30 1 30 62 B 4E 78 5b 94 6E 110 7E 126 17 37 57 15 77 117 151137 157 15 177 SI US L RUBOUT F 15 1F 31 2F 47 3F 63 Bl 4F 79 5F 95 9 6F 111 7F 127 ADDRESSED UNIVERSAL LISTEN TALK SECONDARY ADORESSES COMMANDS COMMANDS ADDRESSES ADDRESSES OR COMMANDS REF ANSI STD X3 4 1977 IEEE STD 488 1978 ISO STD 646 1973 octal 25 PPU GPIB code N AK ASCII character 15 hex 211 decimal Figure A 3 ASCII amp GPIB Code Chart 4415 23 IEEE STD 488 GPIB System Concepts 494AP Programmers To summarize the difference between interface con trol messages and device dependent messages on the data bus remember th
42. 488 GPIB connector A 1 4 7 Front panel General Purpose commands 4 33 2 Atypical GPIB A 3 A 3 ASCII amp GPIB Code A 5 A 4 example of data byte traffic on the 7 5 A typical handshake timing sequence A 7 Table Table Number Page Number Page 11 AdOIUBSOB oi sci ccssncecicvvsivensinssansccivissevseeiscesenss 1 3 9 1 Marker Trace 5 2 1 2 Spectrum Analyzer IEEE 488 Interface PIED ws rayYuE a EERERRELS ER Mi 1 4 0 1 Error Massagss 6 14 4 1 Front panel Commands and Queries 4 1 9 1 Instrument 1 9 6 4 2 X Ranges for the TUNE FIRST SECOND 9 2 Warning 9 8 FRQRNG STEP SPAN and MTUNE 9 3 Test Conversion 9 12 T bs on x x Een e xd 4 2 9 4 Error and Event 9 14 4 3 Resolution Bandwidth Selection 4 13 4 4 Reference Level 4 17 10 1 Execution and Transfer Times 10 14 4 5 Calibration 4 19 A 1 Major GPIB Interface Functions
43. 5 6 12 FER FL 6 12 R 6 12 6 13 General Purpose 6 13 6 14 RUN 6 14 DONIS 6 14 6 14 KILL sicucxnccccautuxtinndecscsecsrevercaiesavet bens 6 15 6 15 6 15 MEMORY ooa t asd 6 15 STNUM EHT 6 15 pls 6 16 enero deve dui vani 6 16 b SERT RENE em 6 16 baked wee 6 16 6 17 INPNUM 6 17 DISPLAY DATA AND CRT READOUT 1 0 NUMUSe in 7 1 Waveform 7 1 WEMP 7 1 CURVE rierren 7 4 WAVER vicscvcccecesctescnnsnssertused ccsvenssses 7 5 DPRET 7 5 DOOPT T ean Rua E VU d 7 6 Crt Readout 7 6 ROOL 7 6 TEXT PEDRO 7 7 LIPPE 7 7 MDMDOT SERI 7 7 7 7 WAVEFORM PROCESSING Use in roe oae no roo
44. A On Of on sB savEA B SAVEA On On jor of Full On Jot A On On On on B A Not applicable Since no digital storage traces are being viewed there is no visible marker The listed trace is that for which marker readouts are given Interaction MTRACE SECOND sets MARKER to DELTA If MARKER is OFF MTRACE or MTRACE PRIMAR sets MARKER to SINGLE e Arguments A B and BMINA set SAVEA ON BMINA sets BMINA ON e Argument FULL sets SAVEA OFF SAVEA OFF moves any marker s on A or B to FULL SAVEA ON moves any marker s on FULL to A or B according to Table 5 1 e f BWMODE is ON one MTRACE command will move both markers to the same trace If the marker is moved off the active trace it will go back to the active trace if the instrument is in MAX SPAN when it is returned to local control e if either marker is placed on a zero span trace the other marker will move there also MTRACE marker trace position query MTRACE or MTRACE PRIMAR The trace con taining the Primary marker is returned MTRACE SECOND The trace containing the Secondary marker is returned Examples MTRACE MTR SEC Response to MTRACE query 2 FULL is returned when SAVEA is OFF A B BMINA B Saved is returned when SAVEA is ON NONE is returned when MARKER is OFF or when MTRACE SECOND is requested while MARKER is set to SINGLE Interaction If HD
45. CRSOR KNOB Successive samples are averaged to obtain the value displayed at each digital storage point The number of samples averaged increases as the sweep is slowed This number is given by Time div 100 9 us Helps and Hints 494AP Programmers Spectrum Search To search a given frequency range for signals set the spectrum analyzer to sweep the given range with FREQ and SPAN or STSTOP If the frequency range is wide and or the number of signals expected is large search the range in sections With the marker or display data point at the left edge of the screen find the lowest frequency signal with the MRGTNX command or the RGTNXT command Find suc cessive signals by repeating the same command All sig nals in the display have been found when the RGTNXT command sets the display data point to 1001 0 or the MRGTNX command generates an SRQ message of NO SIGNAL FOUND If the service request is disabled either through SGERR OFF or RQS OFF the MRGTNX query can be used to determine whether the MRGTNX com mand found FOUND will be returned or did not find FAILED will be returned a signal Signal searches should be done in the single sweep mode take a new sweep only when all signals in one waveform have been found If the total range is being searched in sections move to the next section with a TUNE FREQ STSTOP PSTEP or MSTEP command and repeat the search By positioning the marker or display data point prop erly at t
46. CURVE query are used in the same command line with another CURVE command or CURVE query Whether interaction results in invalid data depends on the relative position of these message units in the mes sage This follows from how these message units use the buffer Buffer Data Flow Data flow through the buffer is diagrammed in Figure 10 2 This figure identifies the kinds of data operations as data paths or destinations branching from the right of the buffer The partitions in digital storage memory are shown as data sources or destinations branching from the left of the buffer The WFMPRE and CURVE commands contain argu ments that set switches to control data flow through the buffer Either the CRVID argument or the WFID argument sets the switch to select A B or FULL A and B memory The ENCDG argument sets the switch that selects either ASCII or block binary waveform output Both switches are shown in their power up default posi tions They remain wherever they are set until changed by an appropriate command WAVEFORM PROCESSING ASCII OR BINARY WAVEFORM INPUT WAVEFORM OUTPUT BLOCK BINARY WFMPRE ENCDG M 3401 157 Figure 10 2 How multiple use of the display data buffer is controlled 10 7 Helps and Hints 494AP Programmers Order Dependent Conflicts Conflicts in the use of the buffer occur depending on the order in which waveform processing and I O occurs The CURVE command
47. Finally restore the spectrum analyzer to the original settings by transmitting the stored SET query response back to the instrument a 4041 program follows that steps you through the operation 300 Rem This program stores recalls spectrum analyzer front panel settings 302 Dim s to 750 310 Print Press Return key to store settings 320 Input k wait for return 330 Input prompt set z s 335 Print Settings stored 340 Print Press Return to recall settings to front panel 350 Input k wait for return 360 Print z s 365 Print Settings recalled 370 End Line 302 Dimensions the string variable Lines 310 through 335 Inputs SET response from the spectrum analyzer Lines 340 through 365 Returns a SET response to the spectrum analyzer Resetting the Spectrum Analyzer and Interface Messages The INIT command resets the instrument s program mable controls to their initial turn on condition see Sec tion 9 in this manual for more on this command INIT is sent in the same manner as other commands Interface message DCL device clear clears the instrument I O buffers and can be used to restart bus communications with the spectrum analyzer DCL does not interrupt message execution If the spectrum analyzer is waiting for its talk address so it can execute an output query output is stopped and the buffers are cleared by DCL decimal code 20 or any device dependent input The decimal codes fo
48. IN on the rear panel The horizontal position of the crt beam and the instrument front end tuning are varied by an external signal A signal in the range 0 to 10 V scans the spectrum Macro Memory Used 5 bytes Examples TIME 1 TIM 10 MS TIME MAN Power up value TIME DIV control setting Interaction Too fast a sweep speed for a given resolution bandwidth will uncalibrate the display For digital storage to properly acquire spectrum data 10 ms div is the maximum usable sweep rate TIME time div query Cre Response to TIME query The SET response includes AUTO as a possible argument see SET under Instrument Parameters in the System Commands and Queries section of this manual 4 26 Instrument Control 494AP Programmers DIGITAL STORAGE These commands control the digital storage functions of display AVIEW BVIEW updating SAVEA comparison BMINA display storage DSTORE display recall DRECAL and digitizer control MXHLD CRSOR SAVEA BMiNA AView DSTore DREcaL A 7 S A 1 BAND k arte 4 787 CENTERIMARKER FREQUENCY FREQUENCY RESOLUTION SPANI DIV BANOWI 5559 10 Figure 4 5 Front panel Digital Storage commands AVIEW A waveform display command ON The A waveform is displayed on the crt The A and B waveforms are independent and may be displayed together or separately however both waveforms will be displayed if
49. Memory Used 1 byte Interaction CNTCF is not available in MXSPN or ZEROSP There is no CNTCF query STSTOP start stop sweep command MARKER The frequency and span are set so that the instrument sweeps over the frequency range delim ited by the markers The lowest frequency marker sets the start frequency and the highest frequency marker sets the stop frequency NUM NUM The starting frequency of the display is set to the first NUM and the ending frequency is set to the second NUM Execution error message 28 is issued if the second NUM is less than the first NUM Macro Memory Used 12 bytes Examples STS MARKER STSTOP 10MHZ 130MHZ STS 100000HZ 66MHZ Range Bands 1 and 6 12 Band limits of the band the start and stop frequencies were set in not the band the instrument is currently in Bands 2 5 Any value within the bands Instrument Control 494AP Programmers Power up value Start frequency 0 Hz stop fre quency 1 8 GHz Interaction Marker execution error message 123 is issued if the STSTOP MARKER command is given when MARKER is not set to DELTA STSTOP start stop sweep query 7 Response to STSTOP query The response is the present start and stop frequency in that order whether the values were entered as start stop frequencies or result from the combination of a center frequency and span DELFR delta frequency command ON The
50. ON and NO is returned There is no RVALID command Instrument Control 494AP Programmers 4 37 Section 5 494AP Programmers MARKER SYSTEM The digital storage functions described in Section 4 of this manual must be on for the marker s to be view able The Primary marker single marker mode displays marker frequency and amplitude A Secondary marker is added to the Primary marker in the delta marker mode and the difference in frequency and amplitude between the two markers is displayed In the delta marker mode the Primary marker is the brighter of the two The GPIB marker commands in this section are divided into four categories system control marker posi tioning marker finding and miscellaneous Use in Macros Most of the marker system commands in this section can be incorporated into macros designed to your specific needs No queries can be used within macros Since there is a total of 8k bytes of memory dedicated for macro use it is important that you know the number of bytes used for each command and keep this in mind while preparing macros This maximum number of bytes used is included with the commands in this section and there is also a table on the pullout page at the back of this manual that lists all available spectrum analyzer commands and the bytes used by each NUM Argument Values Unless otherwise stated the values for the NUM argument are 1 ON 2740 5 are rounded to 1 e 0
51. Output buffer overflow remaining output lost Attempt to execute command in Local mode Frequency out of range FREQ TUNE FIRST SECOND MMAX MMIN MTUNE MFREQ STSTOP STEP FRQRNG out of range CRES out of range SPAN out of range RESBW out of range MAXPWR or MINATT out of range Level out of range REFLVL THRHLD BWNUM MVRTDB MVLFDB VRTDSP LIN out of range VRTDSP LOG out of range TIME out of range IDENTify not allowed in this span div Signal finds not allowed in zero span Invalid DATA or ADDR argument contents DATA direction not compatible with ADDR direction GET Group Execute Trigger ignored not executed NUMEV out of range STORE RECALL DSTORE DRECAL or RDATA out of range PHSLK cannot be turned OFF ON directly with PHSLK command aif this error message is issued the macro in progress will be aborted 9 14 System Commands and Queries 494AP Programmers Table 9 4 Continued ERROR Code Meaning Execution Errors Continued 1012 Function not available when SGTRAK is on 102 Frequency range limited in 75 Q input Option 07 only 103 Frequency out of range after step 104 Bandwidth mode is not available when in linear 105 Illegal sweep range 106 Argument out of range 109 ROFSET out of range Execution Warnings FREQ change caused EXMXR change SPAN defaulted to MAX UNCAL light turned on UNCAL light turned off Multiple use of display buffer STEP defaulted to maximum SPAN defaulted to mi
52. VAR YREG ENTER DISBUF VAR NUM ENTER 100 ENTER 100MHZ Macro Memory Used 10 bytes VAR Range 1 to 30 DISBUF range 1 to 1000 Interaction Before the value of XREG is changed the value in XREG is copied into YREG There is no ENTER query BRANCHING AND LOOPING COMMANDS The branching commands will go to a LABEL GOTO label a point in the macro LABEL create macro looping FOR perform action if statement is true IF return from a subroutine RETURN and go to a Subroutine GOSUB The branching and looping com mands are available only within macros they cannot be used outside of macros Although not discussed separately there are companion commands included here NEXT works with the FOR command and ELSE and ENDI work with the IF command GOTO go to LABELed line command NUM Tells the macro which LABEL to go to and continue execution Macro Memory Used 5 bytes Range 1 to 100 If the macro is instructed to go to a label that does not exist macro execution error message 170 is issued Error message 170 will only be seen after the EMAC command when the macro is compiled and errors are located NOTE The last command in a macro before the EMAC command must be GOTO or RETURN or DONE If it is not macro execution error message 178 is issued There is no GOTO query 494AP Programmers Macros command syn ENTER enter value in X registe tax diagram Macro
53. a plot to be generated The following routine assumes the spectrum analyzer is at address z the plotter is at address P and that the plotter type has been selected with the PTYPE command 70 Z 1 ADDRESS OF SPECTRUM ANALYZER 80 3 ADDRESS OF PLOTTER 100 Print z GRAT ON RED ON PLOT 110 WBYTE ATN 64 z 32 p 120 On EOI 5 then gosub 200 130 Enable EOI 5 140 Wait 150 Stop 200 WBYTE ATN unl unt 210 Resume Line 100 Illuminates the graticule turns the crt readout on and readies the spectrum analyzer to send a waveform to the plotter Line 110 Makes the spectrum analyzer a talker and the plotter a listener Line 200 Untalks the spectrum analyzer and unlistens the plotter Using PLOT With Macros Macro Readout Buffer When the macro readout buffer is displayed it alone will be plotted nothing else will plot even the graticule or waveform Using DSLINE If DSLINE is used to turn off the normal top second or bottom readout lines or replace them with information from the macro readout buffer no labels associated with the lines will be plotted With DSLINE ON any middle line to be plotted will always be plotted in the location where the normal second line would be MULTIPLE USE OF DISPLAY BUFFER An error message alerts you to possibly invalid data caused by multiple use of the display buffer that is using the buffer for more than one purpose during execu tion of a message Also
54. alter the setup some commands are turned off before the setup begins For identification purposes the command headers are always returned in the response to SET query even if HDR is turned off There is no SET command 9 1 System Commands and Queries 494AP Programmers Response to SET query 88 eC DELFR 68 7 MARKER Curr On Ga mal On CLC nO With Option 07 Only RLMODE C O Guo ODOT 0 CONC ECE OED OEO BOOS OGD Gh E ns gt Cena o OnO CEE oe a CoC 9 2 System Commands and Queries 494AP Programmers Response to SET query continued 90 GOH O GW m 2 C co REDOUT c DEDO Mns C 800 ER wa Con Continues t pag 9 3 System Commands and Queries 494AP Programmers Response to SET query continued DLO DETRE ale Att MTRACE PRIMAR SP ale ORDO PRIMAR PRIMAR e CD Gua Sens o d re pang DL On Continued on next page STEP SP SP 9 4 Response to SET query continued DO VO
55. are separated and SAVEA is OFF signals resolved to a single point with very nar row resolution bandwidths compared to span appear in either A memory or B memory but not both Display Data and Crt Readout I O 494AP Programmers With SAVEA ON only the B waveform is filled with data from the current sweep so transfers can involve two unrelated waveforms WFID Either the A or B waveform or both A and B FULL waveforms are selected for data transfers and waveform processing ENCDG Either ASCII coded decimal numbers or binary numbers are selected for data transfer The two arguments may be selected independently or strung together in the same command The WFMPRE command cannot be used within a macro Examples WFMPRE WFID FULL WFMPRE ENCDG ASC WFM WFID A ENC BIN Response to WFMPRE query Power up value Full 1000 point ASCII coded digits Interaction The WFID portion of any previous WFMPRE command or the CRVID portion of any previ ous CURVE command is cancelled A WFID or CRVID other than FULL sets MCPOIN to OFF MCPOIN sets WFID to FULL WFMPRE waveform preamble query qn D c0 CO CO CLE una CE POO 800 73000 eT 0 C 7 C7 On On On C C96 Ona 57 Items that follow the waveform identification and cod ing specify other data packet parameters that refer to
56. at point N Display Data and Crt Readout 1 0 494AP Programmers YOFF is 225 top edge of graticule in log vertical display mode and 25 bottom edge of graticule in linear vertical display mode For example data value 125 graticule center could have the following absolute values CURVE display curve command curve SP YN 40 dBm at 10 dB div with a reference level of 0 dBm YN 0 112 V in linear mode with a reference level of 0 dBm The WFMPRE portion of the SET response includes only the WFID and ENCDG arguments NOTE The instrument should be in the Single Sweep mode and not be sweeping during the CURVE command or query If it is sweeping during the CURVE query it could give erroneous information unless transferring a SAVEA display CRVID The destination A B or FULL is selected for the waveform being sent If this argument is omitted the last CRVID in a CURVE command or WFID in a WFMPRE command takes precedence A or B indicates a 500 point transfer FULL indicates 1000 points NUM This is a sequence of ASCII coded digits delimited by commas between successive numbers BINARY BLOCK Binary block is a sequence of binary numbers that is preceded by the ASCII code for percent 96 and a two byte binary integer representing the number of binary numbers plus one the extra byte is the checksum and followed by the checksum The checksum is the 2 s complement of the modulo 256 sum
57. characters decimal 32 to decimal 94 in the ASCII Code Chart Figure A 3 be used to com pose device dependent messages One example of a device dependent message could be the following ASCII character string MODE V VOLTS 2 5E 3 FREQ 1 0E3 The ASCII character string sent with the ATN line unasserted tells the instrument to set its front panel con trols to the voltage mode and output a 2 5 mV signal at a frequency of 1000 Hz When 8 bit binary codes other than the ISO 7 bit are used for device dependent messages the most significant bit should be on data line 0108 for bit 8 B7 B6 B5 BITS B4 B3 B2B1 SII KEY IEEE STD 488 GPIB System Concepts 494AP Programmers 9 x 1 1 g g i 1 1 NUMBERS SYMBOLS UPPER CASE LOWER CASE 100 0 120 168 140 O 160 16 P p 40 64 50 808 60 96 70 112 1 GTL 21 LLO 61 178 101 1 121 178 141 1 161 17 SOH DC1 1 A Q a q 1 1111 17 31 49941 65 51 818 61 97 71 113 2 22 42 2 62 188 102 2 122 18 142 2 162 18 STX DC2 2 B R b r 2 12 18 22 34 32 50 72 114 23 43 3 63 19 163 19 3 S 3 13 19923 35 33 51 73 115 SDC 4 DCL 44 4 64 20 164 20 DC4 4 t 4 14 20 24 36 34 52 74 116 PPC 25 ppu 45 5 165 21 5 15 21 8 25 37 75 117 26 46 6 66 22 166 22 ACK SYN amp 6 6 16 22 26 38 36 54 76 118 27 47 7 67 23 167 23 BEL ETB 7 g w 7 7117 23 27 39
58. dB more RF attenuation than the MNOISE argument and results in lower signal levels in the analyzer hence less distortion NUM 0 MNOISE 1 MDIST Macro Memory Used 2 bytes Power up value MNOISE Interaction This command affects the gain distri bution obtained with the REFLVL command see also MINATT and MAXPWR RLMODE reference level mode query Response to RLMODE query RGMODE reduced gain mode command This command enables or disables 10 dB of IF gain and RF attenuation reduction when in 10 dB division ON The reduced gain mode is turned on OFF The reduced gain mode is turned off Interaction When IDENT and RGMODE are ON the identify trace moves up instead of down RGMODE affects the maximum reference level you can get with the REFLVL command When not in 10 dB div vertical display RGMODE does not affect the gain distribution Macro Memory Used 2 bytes Power up value OFF RGMODE reduced gain mode query Response to RGMODE query AUTO During several sweeps the spectrum analyzer automatically tunes the PEAK control to peak the largest signal in a window around the display data point refer to the Waveform Processing section later in this manual for information on the display data point When peakin the preselector peaking occurs 1 division or 0 MHz whichever is less on either side of the center Instrument Control 494AP Programmers or marke
59. delta frequency function is turned on As the frequency is changed the crt center frequency readout indicates relative frequency rather than absolute frequency Only the readout operates differently FREQ and FREQ response still refer to absolute frequency The resolution of the readout will be the lesser of the current readout resolution and the readout resolution when DELFR was turned on OFF The delta frequency function is turned off Macro Memory Used 2 bytes Power up value OFF DELFR delta frequency query COLO Response to DELFR query Lena el 4 9 Instrument Control 494AP Programmers DEGAUS degauss tuning coils command A current is momentarily turned off to remove resi dual magnetism in the 1st LO and preselector Macro Memory Used 1 byte There is no DEGAUS query EXMXR external mixer input command ON The front panel EXTERNAL MIXER input is selected which requires an external mixer OFF The coax RF INPUT is selected Macro Memory Used 2 bytes Power up value OFF Interaction The EXTERNAL MIXER input is automatically selected for the waveguide bands FRQRNG 6 and above and cannot be defeated by EXMXR OFF When active this input bypasses the input attenuator so it is up to the operator to prevent input overload EXMXR external mixer input query Response to EXMXR query 65 EXMXR 2 OFF IMPED impedance command Option 07
60. displayed on the screen execu tion error message 28 is issued Macro Memory Used 12 bytes Examples MMIN MMIN 15 0MHZ 19 0MHZ MMI 15 0MHZ 19 0MHZ Interaction If MARKER is OFF sets MARKER to SINGLE There is no MMIN query MRGTNX marker right next command The MRGTNX command moves the Primary marker to the peak of the next signal to the right of the present marker position If no signal peak is found the marker does not move Macro Memory Used 1 byte Interaction If MARKER is OFF MRGTNX sets MARKER to SINGLE If SGERR is ON marker execution warning message 130 is issued if a signal is not found The criteria for a signal are set by the THRHLD and STYPE commands MRGTNX marker right next query Response to MRGTNX query FOUND is returned if the last MRGTNX command found a signal FAILED is returned if the last MRGTNX command did not find a signal If the MRGTNX query is given before any MRGTNX command FAILED 1 returned Marker System 494AP Programmers THRHLD marker threshold command TEE NOTE To ensure the correct response all of the letters in each of the unit mnemonics for the THRHLD command must be entered not just the first three letters as required for other mnemonics The THRHLD command sets the threshold for the marker signal find commands MLFTNX MRGTNX MFBIG HRAMPL LRAMPL SGTRAK PKFIND PKCEN and BWMODE
61. displays messages on the crt in either a 2 line or a 16 line mode TEXT Three crt readout queries return the upper row of characters UPRDO the middle row MDRDO or the lower row LORDO WFMPRE waveform preamble command WrMene X SP The WFMPRE command has no effect on the Marker Finding commands in Section 5 of this manual The WFID path of the waveform preamble command allows the choice of either the A or B waveform or both FULL Following the ENCDG path the waveform pream ble command allows selection of either ASCII coded decimal or binary waveform data The contents of digital storage determine if a half resolution or full resolution waveform is obtained or two different waveforms This is because of the way digital storage is handled in the spectrum analyzer The B waveform is updated with each sweep the A waveform is updated only if SAVEA is OFF The values stored for each waveform are alternate points on the current display i e B A B A B A beginning at the left edge of the screen and moving to the right With SAVEA OFF each waveform is a half resolution replica of data from the last sweep A data points offset by 1 from corresponding B data points Full resolution FULL transfers merge the two waveforms for 1000 data points 100 points div and half resolution transfers A or B separate the waveforms for 500 data points 50 points div If the waveforms
62. e lt 0 5 are rounded to 0 Table 4 2 RANGES FOR THE TUNE FIRST SECOND FRQRNG STEP AND SPAN COMMANDS Freq ist LO ra 2nd LO Tune Maximum Band Range GHz Range MHz Range MHz Range GHz Span div 1 0 1 8 2072 3872 2181 2183 1 8 170 MHz 2 1 7 5 5 2529 6329 718 83 719 17 370 MHz 3 3 0 7 1 2171 6271 718 83 719 17 400 MHz 4 5 4 18 2076 6276 718 83 719 17 1 2 GHz 5 15 21 4309 6309 2181 2183 590 MHZ 6 18 27 2655 4071 2181 2183 790 MHZ 7 26 40 2443 3793 2182 2183 1 3 GHZ 8 33 60 3092 5790 2182 2183 2 6 GHZ 9 50 90 3195 5862 2181 2183 3 9 GHZ 10 75 140 3170 6000 2181 2183 6 4 GHZ 11 110 220 2917 5890 2181 2183 10 GHZ 12 170 325 2998 5841 2181 2183 15 GHZ Instrument Control 494AP Programmers FREQUENCY The commands in this group set and change the instrument center frequency FREQ TUNE and STSTOP set the tuning mode TMODE set the 1ST LO FIRST and the 2ND LO SECOND frequencies enable the tracking generator TGMODE and sideband analyzer SAMODE modes disable tuning corrections DISCOR select the frequency range FRQRNG turn the counter mode on and off COUNT select counter resolution CRES transfer signal count to center frequency CNTCF set frequency step size STEP decrease or increase center frequency MSTEP PSTEP set start stop frequencies STSTOP and start the delta frequency function DELFR apply degaussing current to restore preselector ali
63. either AVIEW or BVIEW is on and SAVEA is off OFF The display of the A waveform is turned off See the ON description for operation with SAVE A off If both AVIEW and BVIEW are turned off the input signal is displayed in real time Macro Memory Used 2 bytes Power up value ON Interaction While SAVEA is ON any updating of the trace display in A is halted AVIEW A waveform display query 4 27 Instrument Control 494AP Programmers Response to AVIEW query BVIEW B waveform display command ON The B waveform is displayed on the crt The A and B waveforms are independent and may be displayed together or separately however both waveforms will be displayed if either AVIEW or BVIEW is on and SAVEA is off OFF The display of the B waveform is turned off See the ON description for operation with SAVE A off If both AVIEW and BVIEW are turned off the input signal is displayed in real time Macro Memory Used 2 bytes Power up value ON BVIEW B waveform display query Response to BVIEW query meram Dm BVIEW SP OFF SAVEA save A waveform command s 027 5 ON The A waveform updating is stopped and the current contents are saved This allows comparison with the B waveform which is continuously updated The information in the crt readout is saved and will be displayed instead of the current instrument settings if only AVIEW is on both BVIEW and
64. from a failure 2nd LO tuning system recovered from a failure Phase lock system recovered from a failure IF count recovered from a failure Power supply regained regulation Frequency reference re locked Unrecognized event occurred System Events Power on Operation complete User request Power just came on Operation complete end of sweep SRQ was requested Marker Execution Errors MKTIME not available unless in zero span mode MKTIME out of range Frequency out of range because marker is on inactive trace Function not available when marker is on an inactive trace Function not available when marker is off Function not available when delta marker is off Function not available in BWMODE Function not available when marker is on a B SAVEA trace Function not available when in dB Hz Marker Execution Warninc Signal find commands could not find a signal Signal find commands could not find signal MLFTNX MRGTNX MFBIG HRAMPL LRAMPL PKFIND MVRTDB MVLFDB Macro Execution Errors Command not available when entering a macro Command only available when entering a macro Command only available when a macro is stopped Memory full macro entry refused Number is already used No macro is stored at NUM No more MDATA commands to read Too many GOSUBs with no return RETURN command not expected Line number used more than once DSLINE command Missing LABEL Missing ENDI Missing NEXT ELSE command not expected ENDI command not exp
65. is engineering units may be appended to a number argument The instrument treats the combined number and units as scientific notation where the first letter of the units element represents a power of 10 1 3 G 1E 9 and M 1E 3 or 1 6 the value of M depends on the function where MSEC stands for 1E 3 milliseconds in the TIME time div command and MHZ stands for 1 6 megahertz in the SPAN span div command Only the first letter of the units element is of importance the rest of the units element i e SEC or HZ does not contribute 2 3 Device Dependent Message Structure and Execution 494AP Programmers to the value of the command argument and can be omit ted This does not apply to the dBm and dBmvV units in use with the RLUNITS REFLVL and MAXPWR com mands where all letters must be used to avoid an error Although more than one format character may precede the units only a space SP is shown in the command syntax diagrams in this manual In most cases other than RLUNITS REFLVL and MAXPWR if no units element terminator is sent with the number one of the following will be implied as the default condition depending on usage Volts dB seconds or Hz Character Argument Arguments may be either words or mnemonics ON and OFF for instance are arguments for the commands that correspond to spectrum analyzer front panel push buttons like VIEW B Link Argument The bottom path in the argument dia
66. manual and instruc tions for putting spectrum analyzer waveform processing to work are given in Section 10 of this manual Getting Started 494AP Programmers Getting Smarter Another Way The following 4041 program will measure the ampli tude and frequency of the 100 MHZ CAL OUT and the next 9 harmonics of the CAL OUT signal 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 500 Dim m 20 910 Print z init time auto min 0 span 1m ref 20 920 Print amp z vid nar step 100m sig 530 Print z pstep sig wai mfbig mlocat rep 9 540 Input dein z m 550 Print m Line 500 Dimensions array m Line 510 Initializes the spectrum analyzer and sets the time division minimum attenuation frequency span and reference level Line 520 Sets the video filter establishes a step size of 100 MHz and enters the single sweep mode Line 530 Increases the primary marker frequency by the step value 100 MHz starts a sweep waits until the end of sweep finds the largest on screen signal and requests the marker frequency and marker amplitude and then repeats the sequence 9 more times Line 540 Inputs all 10 marker frequencies and marker amplitudes Line 550 Prints all 10 marker frequencies and marker amplitudes 3 5 Section 4 494AP Programmers INSTRUMENT CONTROL Commands and queries for instrument control are grouped in this section according to the following func tions the marker related commands
67. not be indicated the units will be the current reference level units RFATT RF attenuation query Requests the current value of RF attenuation Response to RFATT query co There is no RFATT command PLSTR pulse stretcher command ON The fall time of detected signals is increased So very narrow pulses in a line spectrum display can be seen The effect is apparent for signals analyzed at reso lution bandwidths that are narrow compared to the span It may be necessary to turn on the pulse stretcher for digital storage of such signals especially if the cursor is set high enough to average them Pulse stretcher may be required to view and store fast pulsed signals For short pulses the signal may exist for less time than is required for a point to be digi tized causing either no value or too low a value to be stored OFF The pulse stretcher is turned off Instrument Control 494AP Programmers Macro Memory Used 2 bytes Power up value OFF PLSTR pulse stretcher query Rcs Response to PLSTR query ay VIDFLT video filter command OFF Both the wide and the narrow video filters are turned off WIDE A filter is turned on in the video amplifier after the detector to average noise in the display The wide filter reduces video bandwidth to about 1 30 of the selected resolution bandwidth NARROW The narrow video filter reduces video bandwidth to about 1 30
68. number and the last macro that was run will be run again e RUN 1 is sent Any negative number is illegal and the macro in the 0 location will be run There is no RUN query DONE macro execution finished command EDEN pow The DONE command tells the spectrum analyzer that macro execution is finished Every macro must include the DONE command unless the macro is in a continuous loop e g a routine that measures bandwidth at the end of each sweep is in a continuous loop If DONE is encountered while the instrument is under remote control the current settings of TIME DIV MIN RF ATTEN dB and PEAK AVERAGE are held DONE in local control resets the controls to their front panel settings Macro Memory Used 1 byte NOTE The last command in a macro before the EMAC command must be GOTO or RETURN or DONE If it is not macro execution error message 178 is issued There is no DONE query EMAC end macro command The EMAC command tells the spectrum analyzer that entering input for a new macro is done The spectrum analyzer then stops storing compiles the macro and checks for errors Table 6 1 lists the errors that may be sent when the macro is being compiled Table 6 1 ERROR MESSAGES Error Number Description 106 Argument out of range LABEL 169 Line number used more than once DSLINE command 170 Missing LABEL 171 Missing ENDI 172 Missing NEXT 173 ELSE command not expected 174 END
69. number of points scaling and error checking NR PT Specifies either 500 or 1000 points in the curve to follow PT FMT Y indicates all curve data is Y display vertical values The data is ordered each point s X display horizontal value is determined by its point number and parameters in the waveform preamble PT OFF Relates the first point to the X origin by the point offset XINCR Is the difference between adjacent data points XZERO Points to the X origin XUNIT Identifies the horizontal display units in hertz seconds or divisions YOFF Relates Y data to the Y origin by the Y Offset YMULT Scales the Y values YZERO Points to the Y origin YUNIT Identifies the units that apply to the Y values dBm dBmV dBuV mV aV nV or volts BN FMT RP Means each binary number single byte stands for a binary positive integer BYT NR 1 Means that binary numbers or ASCII coded digits are transferred as single bytes BIT NR 8 Indicates the precision max number of significant bits of the binary numbers CRVCHK CHKSMO Specifies that the last byte of a binary transfer is a 2 s complement modulo 256 check sum for the preceding bytes except for the first byte which is a percent sign BYTCHK NULL Indicates no byte check is appended to binary data transfers X Axis Scaling X axis specifications XINCR PT OFF and XZERO are used to interpret the po
70. of r 5 Macro Memory Used 1 byte There is no EXCHG query INTEGR convert X register to an integer com mand The INTEGR command truncates the number currently stored in XREG into an integer Examples XREG CONTENTS Before INTEGR After INTEGR 123 45 123 1 96432 2 196 4 83723 E 20 4 83723 20 no effect Macro Memory Used 1 byte There is no INTEGR query POP put Y register into X register command The POP command duplicates the current contents of YREG and puts this into XREG The following example illustrates the use of the POP command 90 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Print z ENTER 5 110 Print z ENTER 10 120 Print z POP 130 Print z STNUM 1 140 Print z VAR 1 150 Input z r 160 Printr Line 100 Enters 5 into XREG Line 110 Moves the contents of XREG to YREG and enters 10 in XREG Line 120 Duplicates the contents of YREG 5 and puts the result in XREG now also 5 Line 130 Stores the contents of XREG in variable number 1 Line 150 Puts the contents of variable number 1 into r 6 3 Macros 494AP Programmers Line 160 Prints the contents of r 5 Macro Memory Used 1 byte Interaction YREG will remain unchanged after the POP command There is no POP query ENTER enter value in X register command The ENTER command syntax diagram is on the fol lowing page The ENTER command in a macro works much like a query
71. of the spectrum analyzer ON The sideband analyzer mode is turned on OFF The sideband analyzer mode is turned off Macro Memory Used 2 bytes Power up Value OFF SAMODE sideband analyzer mode query Response to SAMODE query CD 1 DISCOR disable tuning corrections command This command is included to allow disabling of the frequency control loop in the instrument for speed or diagnostics purposes It will also allow a fallback to low accuracy center frequency operation if the frequency control loop fails ON Center frequency corrections are disabled OFF Center frequency corrections are enabled Macro Memory Used 2 bytes Power up value OFF DISCOR disable tuning corrections query Response to DISCOR query CID Co 4 6 FRQRNG frequency range command NUM The instrument accepts number arguments in the range of 1 through 12 and changes the frequency range accordingly Non integer values are rounded If the number is too large or too small the programmable spectrum analyzer maintains its current frequency range and reports execution error message 29 INC The instrument changes to the next higher frequency range if possible DEC The instrument changes to the next lower frequency range if possible Macro Memory Used 2 bytes Power up value Frequency Range 1 Interaction The instrument automatically selects the
72. of the crt Each succeeding line of characters is displayed at the bottom of the crt and the previous bottom line moves to the top discarding the previous top line Thus each new RDOUT command causes the spectrum analyzer readout to scroll NOTE All characters are displayed as upper case characters In the TEXT LONG mode the screen is completely blanked and up to the first 40 remotely entered charac ters are displayed in the 1st line at the top of the crt screen Successive lines of characters are entered on the following lines until the 16th bottom line is reached Then as each successive line of characters is entered the entire screen scrolls up one line the first line is dis carded and the new RDOUT command characters become the 16th line NORMAL Normal spectrum analyzer readout is restored Macro Memory Used 41 bytes Power up value Normal readout Interaction If a crt message sent with RDOUT remains on the screen after the spectrum analyzer is returned to local control normal readout can be restored by changing an control that causes the normal readout to be updated TEXT LONG will blank the screen There is no RDOUT query TEXT text mode command MACRO SHORT The readout is switched to the normal 3 line mode with a spectrum display When the RDOUT commands used the normal readout is not displayed and customer specified characters are sent to the top and bottom lin
73. signal INIT FREQ 100MHZ SPAN 1MHZ FMAX POI In the preceding example the spectrum analyzer will not have made a full sweep at 100 MHz frequency and a span of 1 MHz before the FMAX POI is executed because there is no WAIT included in the command and you don t know where the sweep was when it went to 100 MHz The following command line is better but you will still have an error INIT FREQ 100MHz SPAN 1MHZ WAIT FMAX POI In this example you still don t know where the sweep was when it went to 100 MHz the screen may not have been updated The WAIT will tell the spectrum analyzer to wait for the end of the sweep before looking for the maximum point FMAX The sweep may not have swept the full 10 divisions with a span of 1 MHz and a center frequency of 100 MHz Right Way In order to satisfactorily center a given signal be sure to incorporate the SIGSWP command in your program as in the following example INIT FREQ 100M SPAN 1M SIG SIG WAI FMA POI In this example the first SIGSWP puts the spectrum analyzer into the Single Sweep mode The second SIGSWP starts a sweep and the WAIT tells the spec trum analyzer to wait for the sweep to end before exe cuting the FMA POI commands RUNNING PROGRAMS WITHOUT A CONTROLLER MACROS Most of the programming examples in this section can be incorporated into macroinstructions macros designed to meet your particular needs The examples in this section that contain commands th
74. spectrum analyzer responds by sending its status byte over the bus The following table explains the messages returned by the spectrum analyzer 1 on 0 X don t Power on status This is set when the instrument is turned on only if an internal switch is set otherwise SRQ is not asserted at power up and power on status does not exist If selected by the switch this status can not be masked by the RQS command The instrument is shipped with this switch off Refer switch selection to qualified service personnel End of sweep status This is set when the spec trum analyzer completes a sweep of the selected spec trum it indicates that digital storage has been updated Ordinary operation status This exists whenever there is no other status condition nothing out of the ordi nary to report Command error This occurs when a message cannot be analyzed or recognized Execution error This results when a message 1 analyzed and is recognized but cannot be executed such as FREQ 999GHZ Internal error This indicates that the spectrum analyzer has discovered a malfunction that could cause the instrument to operate incorrectly Execution warning This results from a command that the spectrum analyzer has performed but has a potential for error An example is RESBW 10 KHZ in the maximum span mode The spectrum analyzer sets the warning status because the UNCAL indicator is lit 0 1 0 X 0 0 0
75. the range of X values for the display data point is always 1 to 1000 2 The waveform processing commands in this sec tion that update the display data point use the same buffer memory as display data 1 0 therefore commands for these two functions can interact if executed as part of the same message This command interaction can cause invalid data output with either CURVE or CURVE When two particular conditions exist together it can cause CURVE data output commands to be invalid 1 if CURVE is followed by a command to update the display data point and 2 if digital storage is updated during the execution of the message either by repetitive sweeps or by the SIGSWP command When both of these conditions exist the curve data output that follows completion of the entire mes sage wil not be the data that was loaded in the buffer at the time CURVE was executed Instead the curve data that is output will be the data that was loaded by the later command to update the display data point because this later data overwrites the data already loaded in the buffer at the time CURVE was executed The curve data is output as expected if CURVE follows the command to update the display data point instead of preceding it because no conflict occurs in the way the commands use the buffer 3 VRTDSP LIN interacts with FIBIG RGTNXT and LFTNXT because they transform linear data into loga rithmic data before execution This interacti
76. the spectrum analyzer address to variable z as previ ously discussed It is also assumed your input and out put character strings will fit p and r respectively This gets further attention with regard to the instrument set tings query SET our next topic 200 On srq then call err hndl 210 Enable srq 220 Print ENTER MESSAGE 230 Input p 240 Print z p 250 Input 2 260 Print r 270 Goto 220 280 End 300 Sub err hndl 305 Integer e 310 Input prompt err 2 320 Print ERROR 330 Resume 340 End 3 3 Getting Started 494AP Programmers Acquiring Instrument Settings with the SET Query The SET query enables the controller to learn spec trum analyzer settings both for reference and to be able to restore the instrument to those settings This query readies the instrument to output a message that includes a response for each programmable function The format of the response allows it to be used to restore the instrument settings with no operator manipu lation required First set up for the measurement and try it from the spectrum analyzer front panel Store the message as it is transmitted by the spectrum analyzer using the SET query Your controller must be ready for a long character string Dimension a string variable large enough for at least 750 characters for the SET query response although the exact size depends on the current settings Then perform any desired instrument operations
77. to corresponding programming information from the GPIB Remote Only the system controller is permitted to assert the REN Remote Enable line whether or not it is the controller in charge at the time When the system controller asserts the REN line an instrument on the GPIB goes to a remote mode when it is addressed as a listener with its listen address not before An instrument remains in a remote mode until the REN line is released high or an optional front panel Switch on the instrument is activated to request the local mode or a GTL Go To Local command is received while the instrument is enabled as a listener However the controller can disable the instrument s front panel return to local switch es by sending a LLO Local Lockout command The LLO command must be preceded or followed by a listen address MLA to cause the instrument to go to a remote mode with front panel lockout The UNL Unlisten command does not return an instrument to the local mode When the REN line goes false it must be recognized by all instruments on the bus and they must go to the local mode within 100 us If data bytes are still being placed on the bus when REN goes false the system pro gram should assure that the data bytes are sent and received with the knowledge that the system is in a local mode not remote T TE and L LE Talker and Listener Functions NOTE Although discussed under one heading the T TE and L LE functions are in
78. to be printed the string may be up to 29 characters There is no PRINT query Macros 494AP Programmers PRINT print number or string command syntax diagram DATA COMMANDS The data commands store numeric data read data and store it into the X register READ and restore the data pointer MRESTO MDATA store numeric data command 6 12 CHARACTER _ CHARACTER a 9 NUM The numeric data to be used with the READ command is stored The program with the MRESTO command illustrates the use of the MDATA command Macro Memory Used 9 bytes There is no MDATA query READ read and store in XREG command The READ command reads the number at the current position of the DATA pointer and puts that value in XREG The macro starts looking from where the pointer is and looks until it finds the first MDATA command The value of the number is put in XREG and the pointer now points to the next command in the macro The program with the MRESTO command illustrates the use of the READ command Macro Memory Used 1 byte Interaction The data pointer is set to the first com mand in the macro when the macro is started If there are no more MDATA commands for READ to read macro execution error message 166 will be issued There is no READ query MRESTO restore data pointer command wa NUM The MRESTO command sets the DATA pointer to the first command in the macro if NUM is
79. to spectrum analyzer 470 Print 2 Check for error 480 Input z err 490 If err ERR 0 then return If no error then return 500 Print err Print error 510 Stop Stop 520 Mdone print All done No errors G PASS FAIL HARMONIC TEST Line 100 Store the following macro in menu position 2 and title it PASS FAIL HARMONIC TEST Line 110 Turn on a single marker do a sweep and move the marker to the signal peak Line 120 Clear line 4 in the macro readout buffer and display the normal top and marker readout and line 4 in the macro readout buffer Line 140 Center the marker put the marker frequency into the step size turn on delta markers and do a plus step Line 150 Take a sweep set the threshold to 60 dBm and move the marker to the signal peak Line 170 If there is no signal print TEST PASSED on the fourth line of the screen indented 10 spaces from the left Line 190 If there is a signal print TEST FAILED on the fourth line of the screen indented 12 spaces from the left Line 210 Move the marke back to the fundamental and set the threshold to auto Line 230 If no fundamental frequency was found print NO SIGNAL FOUND on the fourth line of the screen indented 2 spaces Line 250 Set the Triggering to Frerun and turn the markers off Line 260 The macro is done running Line 270 This is the end of the macro entry Appendix B 494AP Programmers PASS FA
80. 0 of the selected resolution bandwidth NUM 0 OFF 1 WIDE 2 NARROW Macro Memory Used 2 bytes Power up value OFF Interaction It may be necessary to reduce sweep speed TIME to maintain a calibrated display unless TIME is in AUTO because the instrument s overall bandwidth is reduced by video filtering VIDFLT video filter query Response to VIDFLT query LEHO 4 23 Instrument Control 494AP Programmers SWEEP CONTROL Three commands control the instrument sweep which is used both to sweep the frequency span and the crt display These commands control the sweep triggering and mode TRIG and SIGSWP and sweep rate TIME Selection of TIME AUTO directs the instrument to automatically match the sweep to related instrument parameters Other options include manual or external analog control of the sweep TUNE cre wane oz ar n es 47 CENTERIMARKER FREQUENCY v FREQUENCY RESOLUTION SPAN DIV BANDWIOTH REF VIDEO RESOL RANGE OFC FILTER SANOWIOTH Figure 4 4 Front panel Sweep Control commands TRIG triggering command FRERUN The instrument sweep is allowed to run repetitively A trigger is not required and is ignored so the instrument generates a sweep immediately after the hold off period that follows the previous sweep This is a simple and common setup used to acquire a spectrum for manual operation INT The spectrum analyzer generates a sweep only when it i
81. 1 1 ENTER NUMBER OF HARMONICS TO LOOK FOR 6 17 Macros 494AP Programmers 130 Print z PRINT 5 8 ENTER 140 Print amp z PRINT 14 1 RANGE 1 to 10 150 Print amp z INPNUM 5 20 UNSIGN DSTERM Line 100 Clears the macro readout buffer Line 120 Prints the statement on line 1 of the screen beginning at character position 1 Line 130 Prints the statement on line 5 of the screen indented 7 character spaces Line 140 Prints the statement on line 14 of the screen beginning at character position 1 Line 150 Prepares to enter a number on line 5 of the screen indented 19 character spaces Since UNSIGN and DSTERM are used the front panel dB pushbutton will light and the words END WITH will be on the screen on line 7 with an underline on line 8 Macro Memory Used 5 bytes Range The range of the first NUM is 1 to 12 if DSTERM is used or 1 to 15 if DSTERM is not used The range of the second NUM is 1 to 20 There is no INPNUM query LINE 1 NO OFFSET ENTER NUMBER OF HARMONICS TO LOOK FOR LINE 5 OFFSET 8 ENTER NUMBER OFFSET 20 LINE END WITH DB LINE 6 LINE 14 NO OFFSET RANGE 1 TO 10 LINE 16 PRESS SHIFT TO ABORT ALWAYS PRESENT 5559 14 Figure 6 1 INPNUM example 6 18
82. 1 65 81 Power on 0 X 0 X 0 0 1 0 2 18 66 82 End of Sweep 0 0 0 X 0 0 0 0 0 16 Ordinary operation 0 X 1 X 0 0 0 1 33 49 97 113 Command error 0 X 1 X 0 0 1 0 34 50 98 114 Execution error 0 X 1 X 0 0 1 1 35 51 99 115 Internal error 0 X 1 X 0 1 0 1 37 53 101 117 Execution error warning 0 X 1 X 0 1 1 0 38 54 102 118 Internal error warning Four bit status code Spectrum analyzer busy condition Abnormal 1 normal 0 condition SRQ is asserted depends on RQS and EOS commands 5559 15 Internal warning This reports that a non fatal operating condition has been detected Busy This is reported whenever the spectrum analyzer acts on a message in its input buffer This includes the WAIT command while waiting the spectrum analyzer reports busy status Effect of Busy on Device Dependent Messages The spectrum analyzer will not accept further device dependent messages while the busy condition exists if made a listener it asserts NRFD Commands that require interaction with the hardware can keep the spectrum analyzer busy for a second or more significant to some bus controllers for instance commands such as DEGAUS and INIT in the Count mode The waveform processing commands can also require significant pro cessor time Of course long messages such as the SET response take a while to execute see Execution Times Table 10 2 in Section 10 of this manual Although output operations such as the CURVE response ma
83. 1 division from the marker and it will turn the marker on if off Macro Memory Used 4 bytes Examples PEAK PEA AUTO PEAK 512 PEA STO Power up value KNOB MANUAL PEAK control on Interaction AUTO may be used when the external mixer is being used or with the internal mixer in bands 2 through 5 Under the conditions where AUTO may not be used peaking is not used and the stored number or knob position has no effect PEAK peaking query Response to PEAK query 4 21 Instrument Control 494AP Programmers MINATT minimum RF attenuation command NUM The gain distribution set by the instrument is limited RF attenuation may not be reduced below the attenuator step in the number argument If NUM is not an even decade from 0 to 60 the next higher step 0 10 20 60 is selected If the number selected is out of range execution error message 33 is issued INC or DEC The minimum RF attenuation is changed to the next higher or lower step if any Macro Memory Used 2 bytes Examples MINATT 20 MIN 42 DB MINATT INC Range 0 to 60 Power up value MIN RF ATTEN dB control set ting Interaction The range of RF attenuation is limited in response to the REFLVL command which limits the range of the REFLVL command The previous limit set by either MINATT or MAXPWR is cancelled MINATT minimum RF attenuation query MiNATT Response to MINATT query
84. 90 Print z STMAC 7 SIGNAL TEST 100 Print z SWEEP MFBIG 110 Print Z CLEAR 2 120 Print z IF SIGNAL 130 Printz PRINT 2 10 TEST PASSED 140 Print z ELSE 150 Print z PRINT 2 10 TEST FAILED 160 Print z ENDI 170 Print z DSLINE TOP 2 BOTTOM 180 Print z DONE 190 Print z EMAC Line 90 Stores the following GPIB commands as macro number 7 in the macro menu and titles it SIGNAL TEST The commands will not be executed just stored in memory Line 100 Takes a sweep and the marker finds the biggest signal Macros 494AP Programmers Line 110 Clears line 2 of the macro readout buffer Line 120 If a signal is found the test is passed Line 130 Prints the test passed message to the buffer Line 140 If a signal is not found the test failed Line 150 Prints the test failed message to the buffer Line 160 This is the end of the IF command Line 170 Displays the normal top and bottom lines and prints the test results on line 2 Macro Memory Used IF is 23 bytes ELSE is 4 bytes and ENDI is 1 byte Interaction The IF command requires an ENDI end of the IF statement command If the ENDI is miss ing macro execution error message 174 is issued and macro entry is aborted The ELSE command is optional with the IF command There is no IF query PRINT COMMANDS The print commands will clear the macro readout buffer CLEAR display a line DSLINE select data f
85. ABLE OF CONTENTS lii LIST OFILLVSTRATIONS vii LIST OF TABLES cccissscrsosssssccscsccccsiscscscorvscecsanseseccseencees vii SAFETY viii Section 1 INTRODUCTION TO GPIB OPERATION GPIB Pushbutton and Indicators 1 1 RESET LOCAL REMOTE 1 1 Blue SHIFT 1 2 Green SHIFT SRQ 1 2 VP lllo 1 2 GPIB Function Readout 1 2 Setting the GPIB ADDRESS Switches 1 2 Setting the LF OR EOI Switch 1 3 Setting the TALK ONLY and LISTEN ONLY 1 4 IEEE 488 Functions 1 4 Source Handshake SHh1 1 4 Acceptor Handshake 1 1 5 IL 41 1 5 Listener 153 ccisiscscsccenssosserosesssvessneieeie 1 5 Service Request SR1 1 5 Remote Local 11 1 5 Parallel Poll PP 1 5 Device Clear 1 1 5 Device Trigger DT1 1 5 Controller 1 5 Connecting to a System 1 5 Section 2 DEVICE DEPENDENT MESSAGE STRUCTURE AND EXECUTION Syntax 5 2 1 Spectrum Analyzer Input Messages 2 1 Input Message Format 2 1 Message Uni
86. Amplitude mode is active when both FINE reference level steps and a scale factor of 4 dB div or less are selected In this mode the crt VERT DISPLAY readout initializes to 0 00 dB Changes in reference level are displayed as the difference between the initial level and the new level not the absolute reference level This readout is available with UPRDO REFLVL returns the absolute reference level The initial gain distribution RF attenuation and IF gain is not disturbed changes in reference level are created by an offset in the display This allows signals to be compared with inherently higher relative accuracy The delta amplitude range is 657 75 dB and slides depending on the reference level when the Delta Ampli tude mode is entered OFF Normal steps are restored for reference level changes which cancels the Delta Amplitude mode if active 4 20 Macro Memory Used 2 bytes Power up value OFF Interaction This command along with VRTDSP controls the spectrum analyzer response to REFLVL INC or DEC FINE fine reference level steps query Response to FINE query 22 RLMODE reference level mode command MNOISE The instrument is requested to assign gain distribution with minimum RF attenuation for a given reference level Generally this yields 10 dB less RF attenuation than the MDIST argument and results in less displayed noise but may increase distortion MDIST Generally this yields 10
87. B HP7585B or HP7586B or a Gould 6310 or 6320 plotter Select plotter type with lt blue SHIFT gt SAVE A described in Section 4 of this manual A bus controller is not required lt Green SHIFT gt SRQ This SRQ service request pushbutton sequence gets the controller s attention so it will listen respond to the spectrum analyzer For example if the controller put instructions on the screen in the TEXT LONG mode to set up test equipment etc the last line of the instruc tions might say PRESS lt GREEN SHIFT gt SRQ WHEN READY This would instruct the controller to go on to the next step An SRQ will only be issued if RQS is on ADDRESSED This indicator is lit when the spectrum analyzer is addressed to listen or talk GPIB Function Readout A single character appears in the lower crt readout when the spectrum analyzer is talking T or listening L see Figure 1 2 Two characters will appear in this loca tion if the instrument is talking or listening and also requesting service S or if the instrument is in both the talk only and listen only modes REF LEVEL CENTER FREQUENCY MKR LEVEL MARKER FREQUENCY SPAN DIV Q 906H7 600 0 0 1 8 INT 3MHZ AF FREQ REF VIDEO RESOLUTION ATTEN RANGE OSC FILTER BANDWIDTH TALKER LISTENER SERVICE REQUEST 5559 06 Figure 1 2 Status of active GPIB functions Setting the GPIB ADDRESS Switches The rear panel GPIB ADDRESS switches shown in Figure 1 3 set the value of
88. BMINA off OFF The A waveform updating is resumed Macro Memory Used 2 bytes Power up value OFF Interaction BMINA ON turns SAVEA ON SAVEA OFF turns BMINA OFF SAVEA save A waveform query Response to SAVEA query ON The instrument turns on SAVEA if it is off and then turns on a display of the difference between the A waveform and the B waveform which is continuously updated The difference trace baseline is normally set at graticule center but may be varied with an internal switch refer any changes to qualified service personnel OFF The difference display is turned off Macro Memory Used 2 bytes Power up value OFF Interaction BMINA ON turns SAVEA ON SAVEA OFF turns BMINA OFF BMINA B A waveform display query Response to BMINA query 0 DSTORE store display command 9 5 A The A waveform is stored in the memory loca tion indicated by NUM If the number requested is out of the range limit execution error message 47 is issued B The B waveform is stored in the memory loca tion indicated by NUM If the number requested is out of the range limit execution error message 47 is issued The readout and markers associated with the display are stored with the display Macro Memory Used 3 bytes Examples DSTORE A 4 DST B 2 Range 0 to 8 There is no DSTORE query DRECAL recall display command CR A A w
89. Bs before a RETURN macro execution error message 167 will be issued and the macro will be aborted Macro Memory Used 5 bytes Range 1 to 100 There is no GOSUB query 6 8 IF if statement is true command and ELSE and ENDI P SIGNAL True if the last marker signal find com mand found a signal The marker signal find commands are MLFTNX MFGTNX MFBIG HRAMPL LRAMPL PKFIND MVRTDB and MVLFDB NOSIG True if the last marker signal find com mand did not find a signal The marker signal find com mands are MLFTNX MFGTNX MFBIG HRAMPL LRAMPL PKFIND MVRTDB and MVLFDB VAR Compares the contents of a variable to either another variable the X register the Y register or a number XREG Compares the contents of the X register to either a variable the X register the Y register or a number YREG Compares the contents of the Y register to either a variable the X register the Y register or a number NUM Compares a number to either a variable the X register the Y register or another number IF Comparators Argument Description LESS IF less than GRT IF greater than EQL IF equal to NOT IF not equal to IF less than or equal to IF greater than or equal to The following example illustrates the use of the IF command THIS PROGRAM WILL DELETE ANY PRO GRAM STORED IN MACRO LOCATION 7 70 Z 1 ADDRESS OF SPECTRUM ANALYZER 80 Print z KILL 7
90. Commands Most of the commands in the 494AP are compatible with the other Tektronix Spectrum Analyzer s in the 49X series This allows you to use the programs you created for use with other 49X series instruments There are two commands that have no effect on the operation of the 494AP and their descriptions have not been included in this Programmers manual These are FRCAL and PHSLK Even though they have no effect they will be accepted by the 494A 2 6 Since phase lock cannot be turned off in the 494AP the PHSLK command has no effect However if PHSLK OFF is sent while the instrument is phase locked or PHSLK ON is sent while the instrument is not phase locked execution error message 48 will be issued The PHSLK query will still return the present phase lock status Section 3 494AP Programmers GETTING STARTED Getting started with the spectrum analyzer on the GPIB is a simple matter if you are already familiar with a GPIB controller If not talking to the spectrum analyzer over the bus may be the easiest way to get over any uncertainty you feel about getting started Refer to the Macros section for information on preparing programs that can be stored in the spectrum analyzer memory to be used without a controller The spectrum analyzer speaks a friendly language that includes codes for easier human understanding mnemonics for control of the front panel and to transfer measurement data Put these mnemonics into GPIB i
91. DXN DXMULT N PT OFF XDIV XCENT DXZERO where DXN is the X value in graticule divisions Y Axis Scaling Y axis specifications YGRAT YCENT DYZERO DYMULT and YDIV are used to interpret the position of the ordered points in absolute Y values DYN DYMULT VALN YDIV YCENT DYZERO where DYN is the Y value in graticule divisions VALN is the current data value There is no DPRE command DCOPY copy display query 9 The DCOPY query response is the same as the response to ID WFMPRE DPRE CURVE It allows transmission of information from one device to another in display units so that a hard copy can be made of the display There is no DCOPY command CRT READOUT TRANSFERS Readout messages RDOUT can be displayed on the crt screen in either a 3 line or a 16 line mode or can be put in the macro readout buffer text mode TEXT Three crt readout queries return the upper row of normal readout characters UPRDO the middle row MDRDO or the lower row LORDO 7 6 RDOUT readout message command v Q al iun NORMAL CHARACTER the TEXT SHORT mode the spectrum display remains on the crt the readout is cleared and up to the first 40 characters are displayed across the bottom of the spectrum analyzer crt When the RDOUT command sends a new line of characters it is entered at the bottom of the crt and the previous bot tom line of characters is moved to the top
92. E 0 1 2 See 2 DSLINE TOP 4 8 See 3 DSLINE 1 MARKER 4 See 4 The following examples illustrate incorrect use of DSLINE DSLINE 1 2 1 See 5 DSLINE TOP 1 2 See 6 Example Descriptions 1 Two lines are displayed line 1 from the macro readout buffer in place of the normal top line and line 2 from the macro readout buffer in place of normal marker line 2 Two lines are displayed the result is the same as description 1 above 3 Three lines are displayed normal top line line 4 from the macro readout buffer at the fourth line on the screen and line 8 from the macro readout buffer at the eighth line on the screen 4 Three lines are displayed line 1 from the macro readout buffer in place of the top line normal marker line and line 4 from the macro readout buffer at the fourth line on the screen 5 Line 1 is used twice 6 Line 1 is used twice TOP is displayed on line 1 The following example illustrates the use of the DSLINE command 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Print z CLEAR 110 Print z PRINT 3 0 LINE 3 120 Print z PRINT 7 0 LINE 7 130 Print z PRINT 8 0 LINE 8 140 Print z DSLINE TOP 3 7 150 Wait 5 160 Print z DSLINE 7 MARKER 8 6 10 Line 100 Clears the macro readout buffer Line 110 Puts LINE 3 in line 3 of the macro readout buffer Line 120 Puts LINE 7 in line 7 of the macro readout buffer Line 130 Puts LINE 8 in line 8 of the macro readout
93. F 1 OFF MAX OFF ON OFF OFF OFF LOG 10 DB 0 dBm OFF MNOISE Knob position OFF FRERUN OFF Knob position ON ON OFF OFF OFF KNOB ON OFF 500 225 OFF SHORT OFF 50 N Option 07 Only dBm 0 1 8 GHz ON OFF OFF OFF OFF FREQ CW NONE NONE AUTO Table 9 1 Continued INSTRUMENT FUNCTIONS Mnemonic INIT Value BWMODE OFF TGMODE OFF SAMODE OFF ECR OFF ZETIME OFF RGMODE OFF ROFSET 0 HDR header command m ON The header for query responses is turned on OFF The header for query responses is turned off Macro Memory Used 2 bytes Power up value On Interaction The HDR command has no affect on the SET response since the headers are necessary to interpret the response HDR header query Response to HDR query po 5 HoR SP C OFF MESSAGE EXECUTION The two following commands WAIT and REPEAT affect how the spectrum analyzer executes message units imbedded within other messages WAIT wait for end of sweep command The spectrum analyzer delays action on commands in its input buffer that follow the WAIT command status byte to busy and does not input device dependent mes sages The wait condition is ended in either of two ways 1 WAIT ends if an end of sweep is present If this occurs the controller is allowed to request updated spectrum data and be guaranteed that the data has been updated The request message would be similar to SIGSWP
94. Figure 9 1 TEST Conversion Chart Error Codes The Tektronix Interface Standard for GPIB Codes Formats Conventions and Features specifies device dependent Error codes by category Table 9 4 identifies each general category and lists the codes within that category Following the listing are the specific error messages returned by the spectrum analyzer Error codes are returned in numerical order as they appear in Table 9 4 When the current code s is read the error response is cleared 9 13 System Commands and Queries 494AP Programmers ERROR Code Table 9 4 ERROR AND EVENT CODES Meaning No error Command Errors Command header error Command argument error Missing argument Checksum error Bytecount error Input buffer overflow Illegal numeric format END received in block binary Block binary checksum error Illegal placement of question mark Query not recognized Header not recognized End of message unit not expected arguments missing Character argument not allowed Numeric argument not allowed String argument not allowed Binary argument not allowed Link not allowed for this argument Special argument type not recognized Special argument not allowed Character argument not recognized Input buffer overflow Execution Errors Command not executable in Local mode Settings conflict Argument out of range Group Execute Trigger ignored not executed Output buffer overflow remaining output lost
95. I command not expected 175 NEXT command not expected 177 Index out of range DISBUF INDEX VAR INDEX 178 FOR index is already used There is no EMAC query KILL delete macros command ALL A 82 NUM ALL All macros will be deleted from memory NUM Only macro NUM will be deleted from memory A macro cannot be changed once it is stored in memory it must be deleted KILL NUM and completely re entered There is no KILL query MACRO macro status query The MACRO query will return the current macro status Response to MACRO query OFF There is no macro action RUN There is a macro running MCSTOP There is a macro stopped waiting for the RUN STOP pushbutton to be pressed or the RUN com mand to be sent STMAC A macro is being stored in memory MCSTOP macro stop command The MCSTOP command stops macro execution The macro can be restarted by sending the RUN command over GPIB or by pressing RUN STOP on the front panel MCSTOP always holds the current settings of the TIME DIV MIN RF ATTEN dB and PEAK AVERAGE Macros 494AP Programmers Macro Memory Used 1 byte There is no MCSTOP query MEMORY query CORONE 8 NUM The MEMORY query serves two separate purposes MEMORY query with no argument returns the amount of memory remaining for storing macros from the original 8k bytes reserved for macros MEMORY query with a number argument re
96. I or binary numbers refer to both the WFMPRE and CURVE queries Display Data and Readout 494AP Programmers There is no WAVFRM command DPRE display preamble query DPRE calls for the transmission of the display preamble The display preamble contains numeric data items to be used with corresponding curves to reproduce a display Response to DPRE query cent 9 jC oxzeno CC pxwucr Om OO xov amp 9 C 8 48 9 Grzen 57 9 7 rT a XGRAT 10 Specifies the X horizontal graticule size XCENT Is the X center of the display data in number of divisions relative to the left hand side of the graticule DXZERO 0 Displays the X offset in divisions rela tive to XCENT DXMULT 1 Displays the X multiplier XDIV Displays X divisions unit YGRAT 8 Specifies the Y vertical graticule size YCENT 8 Is the Y center of the display in number of divisions relative to the bottom of the graticule 7 5 Display Data and Crt Readout I O 494AP Programmers DYZERO 9 Displays the Y offset in divisions rela tive to YCENT DYMULT 1 Displays the Y multiplier YDIV 0 04 Displays Y divisions unit X Axis Scaling X axis specifications XGRAT XCENT DXZERO DXMULT and XDIV are used to interpret the position of the ordered points in absolute X values
97. IL HARMONIC TEST IC PASS FAIL TTOM 10 TEST PASSED 12 T ES TT F AILE D N O S IGNA L F O UND i i i 8 Store the following GPIB commands as macro number 1 in the macro menu and title it HARMONIC PASS FAIL NOTE The following commands will not be executed just stored in NVRAM Turn on single markers Take a sweep Move marker to the biggest peak Clear line 4 in macro readout buffer Display normal top and bottom readout and line 4 in the macro readout buffer Center marker signal Put marker frequency into step size Turn on delta markers Plus step tune to harmonic Take a sweep Set threshold to 60 Move marker to peak If no signal was found above 60 then the test passed Print TEST PASSED on line 4 A signal was found so test failed Print TEST FAILED on line 4 Done with IF statement Move marker back to fundamental frequency MINUS STEP Reset the signal threshold to auto No fundamental frequency was found Print NO SIGNAL FOUND on line 4 Turn markers off Done with macro End of macro entry GSNNILNOD SOHOYMW MANUAL CHANGE INFORMATION At Tektronix we continually strive to keep up with latest electronic developments by adding circuit and component improvements to our instruments as soon as they are developed and tested Sometimes due to printing and shipping requirements we can t get these changes immediately into pr
98. L 2 which reads 2GHZ into XREG then sets the center frequency to 2 GHz Line 180 GOSUBs to LABEL 2 which reads 3GHZ into XREG then sets the center frequency to 3 GHz Line 190 Sets the DATA pointer to the first item after LABEL 1 2GHZ Line 200 GOSUBs to LABEL 2 which reads 2GHZ into XREG then sets the center frequency to 2 GHz Line 210 GOSUBs to LABEL 2 which reads 3GHZ into XREG then sets the center frequency to 3 GHz Line 220 GOSUBs to LABEL 2 which reads 4GHZ into XREG then sets the center frequency to 4 GHz Line 240 Sets label marker 2 at this position Line 250 Reads the value in the next MDATA command Line 260 Sets the center frequency to the value in XREG Line 270 Takes a sweep moves the marker to the maximum signal and waits 5 seconds before the next macro command is executed Line 280 The macro returns to the line following the last GOSUB Macro Memory Used 5 bytes Interaction If the macro warning message END OF READ DATA MACRO ABORTED appears on the screen while the macro is running the macro will be aborted at that point There is no MRESTO query GENERAL PURPOSE MACROS The general purpose macros pause macro execution PAUSE start or restart macro execution RUN indicate when the macro is done executing DONE indicate when the macro entry is ended EMAC delete one or all macros KILL query macro status MACRO stop 6
99. MKA Mem TY MARKER MENU fj count FREQ START START DISPLAY TRIGGERING o FREE RUN 7 IQ e ID 570 mmo PEAK STEP ose NTRY view T BSAVE ASSIGN C eR un sran D MANUAL ma P FREQUENCY RESOLUTION SCAN SAMO SONAL SINGLE VERT FREQ REF VIDEO RESOLUTION TRACK SWEEP DISPLAY RANGE OSC FILTER BANOWIDTH RESET READY RF INPUT 507 emu m rd o sione DISTORTION 103 2 e Ben 24 RNAL TIME DIV u EXT MIXERUPRESEL Or 5557 01 TEKTRONIX 494AP Programmable Spectrum Analyzer Section 1 494AP Programmers INTRODUCTION TO GPIB OPERATION The TEKTRONIX 494AP Programmable Spectrum Analyzer adds remote control and automated spectrum data acquisition and analysis to the performance and portability features of the TEKTRONIX 494A non programmable Spectrum Analyzer The spectrum analyzer front panel can be controlled remotely except for those controls intended for local use only such as INTENSITY Waveform processing functions are added to do some spectrum analysis locally The IEEE STD 488 General Purpose Interface Bus GPIB port in the spectrum analyzer rear panel allows it to be used with a wide variety of systems and controll ers the instrument follows the Tektronix Interface Stan dard for GPIB Codes Formats Con
100. Maximum MMAX Move Marker to Minimum MMIN Marker Right Next MRGTNX Marker Threshold THRHLD Move Marker Left x dB MVLFDB Move Marker Right x dB MVRTDB Signal Type STYPE Signal Find Error SGERR Table 4 1 cont Name Mnemonic inemonic Miscellaneous Zoom Zero Time ZOOM ZETIME These commands are related to front panel control functions they are not actually labeled on the front panel The following controls and adjustments are operated only from the instrument front panel no remote control INTENSITY MANUAL SCAN POSITION lt gt AMPL and LOG CAL POWER PEAK AVERAGE cursor other than fully counterclock wise or clockwise positions Use in Macros Most of the instrument control commands in this sec tion can be incorporated into macros designed to your specific needs No queries can be used within macros Since there is a total of 8k bytes of memory dedicated for macro use it is important that you know the number of bytes used for each command and keep this in mind while preparing macros This maximum number of bytes used is included with the commands in this section and there is also a table in the foldout chart at the back of this manual that lists all available instrument commands and the bytes used by each NUM Argument Values Unless otherwise stated the values for the NUM argument are 1 ON 240 5 are rounded to 1 e 0 OFF
101. N Using COUNT CF To go to a narrow span from a wide span without having to span down or re center the signal etc use the CNTCF command Position the signal as indicated previ ously for COUNT check for 20 dB above the noise level and send CNTCF Now select the desired span div It is important to make sure sufficient count resolution CRES is selected for the desired span div The CRES selected should be less than 0 1 of the span div desired If many different span divs are being used it is more convenient to leave CRES set to 1 Hz 100 Print z SIG WAI FMA CEN 110 Print z SIG WAI FMA POI FMI POI 120 Input z X Y X1 Y1 130 If Y Y1 50 then 200 140 Print z CNTCF SPAN s 200 CODE TO HANDLE LOW SIGNAL LEVEL CONDITION Using MCEN To span down around a signal without having to manually span down re center the signal etc use the MCEN command after first having selected the desired signal with one of the marker signal finding commands described previously Then select the desired span div Higher Center Frequency Drift Rate After Tuning After a large center frequency change more than 500 MHz oscillator drift can cause center frequency errors This is especially noticeable at slow sweep speeds at spans just above the point where the 1st LO is phase locked which occurs at either 200 kHz div or 50 kHz div depending upon band Additional delay time after a large frequency change beyond that built into
102. P A space SP must separate the header from any argument s Argument Delimiter A comma must separate individual arguments and a colon must separate link arguments Argument Format The following diagram illustrates that arguments fol lowing the header may be a number a group of charac ters or either a number or a group of characters linked to another argument C CORNA p UNITS CHARACTER CHARACTER ARGUMENT CHARACTER ARGUMENT UNITS CHARACTER CHARACTER ARGUMENT Numbers The defined element NUM is a decimal number in any of three formats NR1 NR2 or NR3 NR1 is an integer no decimal point NR2 is a floating point number decimal point required NUM arguments may serve two functions The first is to select the value of a continuous function for example the center frequency with FREQ In this case if NUM exceeds the range of the function the spectrum analyzer does not execute the command but issues an error mes sage see POINT in Section 4 in this manual for an exception Numbers within the range are rounded The second function of a NUM argument is to substi tute for character arguments in ON OFF or mode selec tion In this case if NUM exceeds the selection range it is rounded to the nearest end of the range No error message is issued Numbers within the range are rounded Units The spectrum analyzer accepts arguments in engineering notation that
103. P function implemented If an instrumentation system has more than one con troller only the system controller is allowed to assert the IFC Interface Clear and REN Remote Enable lines at any time during system operation whether or not it is the controller in charge at the time If a controller requests system control from another controller and it receives a message from another con troller to send REN the system controller must verify that the REN line remains unasserted false for at least 100 us before asserting REN The time interval that REN is asserted depends on the remote programming sequence and will vary with the program The IFC line must be asserted for at least 100 The Controller function has specified time intervals for certain operations For example the execution time for parallel polling instruments on the bus cannot be less than 2 us If the controller is in the controller active wait state and does not receive an internal message to con duct a parallel poll it must wait for at least 1 5 us before going to the controller active state in order to give the NRFD NDAC and EOI lines sufficient time to assume their valid states The controller must also have a delay of at least 2 us 1 1 us for tri state drivers in order for the instruments to see the ATN line asserted before the controller places the first data byte on the bus Taking Control Asynchronous or Synchronous All data bytes transmitted ov
104. P 492AP 495P 495P Option 05 494AP RQS is the master mask for service requests and both RQS and EOS must be on to cause end of sweep service requests 492P 496P RQS masks error service requests and EOS masks end of sweep service requests Only EOS must be on for end of sweep service requests Affect of Busy on Device Dependent Messages 494P 492AP 495P 495P Option 05 494AP Inter face messages are processed despite busy status If RTL interrupts a message the programmable spectrum analyzer executes the remainder of the message before restoring local control The response of the spectrum analyzer to interface messages depends on the manner in which they are handled Some interface messages are handled by the GPIB interface while others require action by the microcomputer The latter generally involve the GPIB address and are implemented in firmware rather than on the interface The speed with which these commands can be handshaked depends on how fast the spectrum analyzer can service the resulting interrupt 492P 496P Interface messages are processed despite busy status if the busy status occurs because the spectrum analyzer is executing a WAIT command If RTL interrupts WAIT the spectrum analyzer attempts to 2 5 Device Dependent Message Structure and Execution 494AP Programmers execute the remainder of the message after restoring local control and waiting for EOS If the busy status occurs because t
105. Primary marker is moved to the largest left most vertical value in digital storage if that value is above the threshold If no value is found above the threshold the marker does not move PKFIND locates the left most peak or the center peak of a cluster but it is not a sig nal processing command with the built in intelligence Peak B would be selected from the cluster in Figure 5 1 peak A would be selected in Figure 5 1B because the low point B would stop a search from continuing to the cluster C MARKER To A MARKER Figure 5 1 Using the PKFIND command Macro Memory Used 1 byte Interaction If MARKER is OFF PKFIND sets MARKER to SINGLE If SGERR is ON marker execution warning message 130 is issued if a value is not found The criteria for a signal is set by the THRHLD command PKFIND does not use STYPE PKFIND marker to maximum above threshold query Response to PKFIND query FOUND is returned if the last PKFIND command found a signal FAILED is returned if the last PKFIND command did not find a signal If the PKFIND query is given before any PKFIND command FAILED is returned PKCEN marker to maximum and center com mand The PKCEN command is a combination of the PKFIND and MCEN commands The Primary marker is moved to the largest left most vertical value in digital storage if that value is above the threshold and the marker is then tuned the marker frequency to the center of the screen
106. R TEST 100 Print z FOR 1 100MHZ 500MHZ 100MHZ 110 Print z ENTER VAR 1 120 Print z PUTREG FREQ MFBIG PAUSE 5 130 Print z NEXT 140 Print z DONE 150 Print z EMAC Line 100 For variable a 100 MHz to 500 MHz in 100 MHz steps Line 110 Enters the value of variable number into XREG Line 120 Sets the center frequency to the value in XREG moves the marker to the biggest signal and waits 5 seconds before the next macro command is executed Line 130 Repeats until variable 1 is greater than 500 MHz Macro Memory Used FOR is 20 bytes and NEXT is 5 bytes Range NUM is 1 to 30 Arguments 2 3 and 4 are 549 755 813 877 maximum value for a 5 byte hexadecimal number Interaction The FOR command requires a NEXT command If the NEXT is missing macro execution error message 172 is issued after the EMAC command has compiled the macro and checked for errors There is no FOR query RETURN return from a subroutine command The RETURN command returns macro control to the line following the last GOSUB command Refer back to the example for GOSUB to see the use of the RETURN command If there is a RETURN without a GOSUB macro exe cution error message 168 RETURN NOT EXPECTED will be issued and the macro will be aborted Macro Memory Used 1 byte Macros 494AP Programmers NOTE The last command in a macro before the EMAC command must be GOTO or RETURN or DONE I
107. R is OFF PRIMAR or SECOND and the following delimiter are eliminated along with the MTRACE header M1ASGN assign marker pushbutton 1 command 5 18 9 Marker System 494AP Programmers The M1ASGN command assigns the marker function that will be called up with the front panel ASSIGN 1 pushbutton For the description of each argument see the description of the command whose mnemonic is the same as the argument Macro Memory Used 4 bytes Examples M1ASGN MRGTNX M1A MVR 100 M1ASGN MVLFDB 80DB Power up value The assignment is stored in memory The power up value is the marker function that was assigned when the power to the instrument was last turned off If no assignment has ever been made MRGTNX is assigned Interaction The M1ASGN command affects only the command that will be executed when the front panel ASSIGN 1 pushbutton is pressed while the instrument is under local control M1ASGN assign marker pushbutton 1 query Response to M1ASGN query C M1ASGN sP MLFTNX 5 3 Marker System 494AP Programmers M2ASGN assign marker pushbutton 2 command MaAsan SP The M2ASGN command assigns the marker function that will be called up with the front panel ASSIGN 2 pushbutton For the description of each argument see the description of the command whose mnemonic is the same as the argument Macro Memory Us
108. RESOL SPAN DIV C e e 10 2 RLUwr FINE 5559 03A Figure 4 3 Front panel Vertical Display and Reference Level commands 4 15 Instrument Control 494AP Programmers VRTDSP vertical display command Power up value LOG 10 dB division SP Interaction The selection of 1 2 3 or 4 dB div with FINE ON causes the spectrum analyzer to enter a delta amplitude mode See FINE for a discussion of this mode VRTDSP vertical display query Response to VRTDSP query REFLVL reference level command EOE LOG The display is scaled to the dB division specified by integers in the range 1 to 15 non integers are rounded VRTDSP LOG values outside this range cause execution error message 36 to be issued LIN The display is scaled in volts division NUM is adjusted to the volts equivalent of the nearest 1 dB div If NUM is omitted the display is scaled to leave the refer ence level at its current value V D 1 8 volts equivalent of REFLVL INC or DEC changes the scale factor to the C wc next step in the 1 2 5 volts division sequence if possi ble when FINE is OFF When FINE is ON the next step DEC is determined by the 1 dB change in REFLVL that INC or DEC causes the new scale factor is 1 8 volts equivalent of REFLVL Out of range values cause the instrument to report execution error message 35 NOTE Macro Memory Used 3 bytes Examples VRT LOG 3 T
109. RTDB command moves the Primary marker to the right and NUM DB down negative NUM or up positive NUM or NUM without a sign from the current position If the requested amplitude cannot be found the marker does not move Macro Memory Used 3 bytes Interaction MARKER is OFF MVRTDB sets MARKER to SINGLE If SGERR is ON marker execution warning message 130 is issued if the requested ampli tude is not found MVRTDB move marker right x dB query Response to MVRTDB query FOUND is returned if the last MVRTDB command moved the marker to the requested position FAILED is returned if the last MVRTDB command could not move the marker to the requested position the MVRTDB query is given before any MVRTDB command FAILED is returned STYPE signal type command CW Continuous wave signals are identified PULSE Pulsed signal groups are identified SPURS All signals above the threshold are identified NUM 0 CW 1 PULSE 2 SPURS Figure 5 2 is a signal enlarged to show how the spec trum analyzer locates the signal peak with one of the sig nal processing commands The signal processing com mands are MLFTNX MRGTNX MFBIG HRAMPL and LRAMPL The spectrum analyzer looks at both the indivi dual left most and right most peaks of a signal From this reading the spectrum analyzer calculates the exact center of the signal If this location is one of the max Marker System 494AP Programme
110. Response to HRAMPL query FOUND is returned if the last HRAMPL command found a signal FAILED is returned if the last HRAMPL command did not find a signal If the HRAMPL query is given before any HRAMPL command FAILED 1 returned LRAMPL next lower amplitude command 5 10 The LRAMPL command moves the Primary marker to the next lower amplitude signal on the display If the marker is on the lowest signal on the display or a signal cannot be found the marker does not move Macro Memory Used 1 byte Interaction If SGERR is ON marker execution warning message 130 is issued if a signal is not found If MARKER is OFF LRAMPL sets MARKER to SINGLE The criteria for a signal are set by the THRHLD and STYPE commands LRAMPL next lower amplitude query 9 Response to LRAMPL query FOUND is returned if the last LRAMPL command found a signal FAILED is returned if the last LRAMPL command did not find a signal If the LRAMPL query is given before any LRAMPL command FAILED is returned BWNUM marker bandwidth number command Bwn Pnu e BWNUM sets the level below the signal peak used the bandwidth mode BWMODE at which the bandwidth is found This number is stored in battery powered memory Macro Memory Used 3 bytes Power up value The value set is stored in memory If a number has never been set or if the memory fails the value will be 6 dB BWNUM marker bandwidth number query
111. SBW query ay RESBW SP The response to the SET query includes the AUTO argument see SET under Instrument Parameters in the System Commands and Queries section of this manual because in AUTO the instrument can determine the bandwidth ARES automatic resolution bandwidth command ON The current span is matched with an appropri ate resolution bandwidth that maintains calibrated perfor mance for the current sweep speed if possible When both auto resolution and auto time are selected resolu tion is selected based on span and time is selected to maintain calibration OFF ARES ON is cancelled leaving the resolution bandwidth at the current value Macro Memory Used 2 bytes Power up value On Interaction ARES OFF also cancels RESBW AUTO ARES is turned off by any RESBW command except RESBW AUTO ARES automatic resolution bandwidth query 4 14 Response to ARES query ARES is not included in the response to the SET query because AUTO is included in the RESBW response IDENT identify command ON The identify function is turned on Spurious conversion products are shifted horizontally on alternate traces The trace is also offset vertically on alternate sweeps so true signals stand out OFF The identify function is turned off Macro Memory Used 2 bytes Power up value Off Interaction The span must be 50 kHz div or less in bands 1 5 50 MHz
112. SIGSWP WAIT WFMPRE CURVE The first SIGSWP command sets the spectrum analyzer to the single sweep mode if it was previously in a repetitive sweep mode The next SIGSWP arms the sweep and WAIT delays further action until the sweep completes The message ends by the request of a waveform preamble and data If the sweep is in the single sweep mode and is not armed the READY light is off when the WAIT command comes up the spectrum analyzer continues to execute the message in the buffer and does not wait 2 WAIT is ended if DCL or SDC while listener addressed is received This empties the input and output buffer so any commands that follow WAIT are discarded See STATUS BYTE later in this section Macro Memory Used 1 byte Interaction WAIT delays completion of any portion of a message that follows until one of the ending condi tions just outlined occurs There is no WAIT query REPEAT repeat execution command 6 Num NUM This determines the number of times in addition to the first time the spectrum analyzer is to repeat the commands or queries that come before REPEAT Range 0 to 16 777 215 2 24 1 Since REPEAT may itself be one of the commands that comes before a REPEAT the nested first REPEAT will only be performed on the first pass through the com mands that come before the second REPEAT For exam ple RGTNXT FREQ REPEAT 10 FREQ 1 4 GHZ REPEAT 1 System Commands and Queries
113. TE re rH Part No 070 5559 01 Product Group 26 494AP SPECTRUM ANALYZER Copyright 1987 Tektronix Inc All rights reserved Contents of this publication may not be reproduced in any form without the written permission of Tektronix Inc Products of Tektronix Inc and its subsidiaries are covered by U S and foreign patents and or pending patents SCOPE MOBILE and are registered trademarks of Tektronix Inc TELEQUIPMENT is a registered trademark of Tektronix U K Limited Printed in U S A Specification and price change privileges are reserved Tektronix Inc P O Box 500 Beaverton Oregon 97077 Serial Number 494AP Programmers PREFACE This manual is one of a set of product manuals for the TEKTRONIX 494AP Programmable Spectrum Analyzer This manual describes the programmable func tions of the spectrum analyzer and how to use them for remote operation The manual organization is shown in the Table of Contents The manuals that are available now in addition to this Programmers Manual are the 494A 494AP Operators Manual standard acces sory 494A 494AP Service Manuals Volume 1 and 2 optional accessories 494A 494AP Operators Handbook optional acces sory and 494AP 495 Option 05 Programmers Reference Guide For manual ordering information contact your local Tektronix Field Office or representative or refer to the Accessories portion of the Replaceable Mechan
114. VEA both ON and BMINA and BVIEW both OFF the returned readout will be the saved readout Refer to the recall display DRECAL or the save A waveform SAVEA commands in Section 4 of this manual There is no UPRDO command MDRDO middle readout query COO Response to MDRDO query 40 CHARACTER STRING CHARACTER Characters are from the middle row of regular crt readout Blanks are transmitted as spaces Regular readout that would be displayed if GPIB did not have control whether visible on the screen or not is the readout returned by the query not a message sent to the instrument by RDOUT Refer to the recall display DRE CAL or the save A waveform SAVEA commands in Section 4 of this manual There is no MDRDO command LORDO lower readout query 8 7 Response to LORDO query Display Data and Crt Readout 1 0 494AP Programmers CHARACTER Characters are from the lower row of regular crt readout Blanks are transmitted as spaces Regular readout that would be displayed if GPIB did not have control whether visible on the screen or not is the readout returned by the query not a message sent to the instrument by RDOUT With AVIEW and SAVEA both ON and BMINA and BVIEW both OFF the returned readout will be the saved readout Refer to the recall display DRECAL or the save A waveform SAVEA commands in Section 4 of this manual There is no LORDO command 7 8 Section 8 494AP Progra
115. WFM command will get the current waveform A amp B and store it in the array DISBUF The purpose of the GETWFM command is to load the waveform so you can use the ENTER DISBUF command The Macro Example below finds the highest point in the display and works like the PKFIND command The highest point is left in XREG The following example illustrates the use of the GETWFM command THIS PROGRAM WILL DELETE ANY PRO GRAM STORED IN MACRO LOCATION 7 70 2 1 ADDRESS OF SPECTRUM ANALYZER 80 Print z KILL 7 90 Print z STMAC 7 GETWFM TEST 100 Print z GETWFM 110 Print z ENTER 0 120 Print z FOR 1 1 1000 130 Print z ENTER DISBUF VAR 1 140 Print z IF YREG GRT XREG 150 Print z POP 160 Print z END I 170 Print z NEXT 180 Print z DONE 190 Print z EMAC Line 100 Gets the current waveform Line 110 Initializes the maximum value Line 120 For 1 1 to 1000 Line 130 Enters DISBUF VAR 1 Line 140 If YREG old maximum value is greater than XREG Line 150 Puts higher value into XREG Macro Memory Used 1 byte There is no GETWFM query Macros 494AP Programmers INPNUM input number command iNPNuM 5 NUM J gt C The INPNUM command allows you to input a number from the DATA ENTRY pushbuttons and store the number in XREG The first NUM sets the line number on which the input number will be printed on the screen The second NUM is
116. YTE in Section 9 in this manual and reports the corresponding status when polled Remote Local RL1 The spectrum analyzer has the complete remote local function The front panel RESET TO LOCAL pushbutton returns the instrument from remote to local control unless the LLO local lockout message was previously received The GTL go to local message also returns the instrument from remote to local control Refer to the discussion under STATUS BYTE in Section 9 of this manual for the effect of busy status on remote local tran sitions The current value of most programmable functions is maintained when switching from local to remote control Only the value of TIME DIV MIN RF ATTEN dB and PEAK AVERAGE may change to match the front panel control settings when switching from remote to local control so they won t conflict with local control The spectrum analyzer must be under remote control to begin executing device dependent messages that change the state of local controls or to load data into digital storage Once begun execution continues even if REN remote enable goes false The spectrum analyzer changes settings for which there is no local control and outputs data while under local control Introduction to GPIB Operation 494AP Programmers Parallel Poll PP1 The spectrum analyzer responds to a parallel poll to indicate if service is requested Device Clear DC1 The spectrum analyzer responds to the DCL device clear
117. a plug in device at secondary address 12 as the final destination of the data to follow The data is the two ASCII characters A and B decimal 65 and decimal 66 Note that the ATN line is asserted for the first two data bytes and unasserted for the device dependent character to indicate the last data byte in the message The controller activates the ATN line again and sends the universal unlisten UNL and untalk UNT commands to clear the bus Six handshake cycles on the data transfer control bus are required to send the six data bytes Transfer Bus Handshake Each time a data byte is transferred over the data bus an enabled talker and all enabled listeners execute a handshake sequence via signal lines DAV NRFD and NDAC see Figure A 5 the ATN line is shown to illus trate the controller s role in the process A 6 DAV Data Valid The DAV signal line is asserted by the talker after the talker places a data byte on the data bus When asserted low DAV tells each assigned listener that a new data byte is on the bus The talker is inhibited from asserting DAV as long as any listener holds the NRFD signal line asserted NRFD Not Ready For Data An asserted NRFD sig nal line indicates one or more of the assigned listeners are not ready to receive the next data byte from the talker When all of the assigned listeners for a particular data byte transfer have released NRFD the NRFD line becomes unasserted high When NRFD
118. a single line is called a uni line message two or more of these messages can be sent concurrently Only multi line messages are discussed here uni line messages are discussed later under GPIB Signal Line Definitions The interface control messages refer to Figure A 3 are sent and received over the data bus only with the ATN attention line asserted true Interface message coding can be related to the ISO International Standards Organization 7 bit code by relating data bus lines DIO1 through DIO7 to bits B1 through B7 respectively in the Bits column in Figure A 3 IEEE STD 488 GPIB System Concepts 494AP Programmers INSTRUMENT A ABLE TO CONTROL TALK amp LISTEN CONTROLLER DATA BUS 8 SIGNAL LINES INSTRUMENT B TALK AND LISTEN DIGITAL MULTIMETER TRANSFER BUS HANDSHAKE 3 SIGNAL LINES INSTRUMENT C LISTEN ONLY SIGNAL GENERATOR INTERFACE MANAGEMENT BUS 5 SIGNAL LINES INSTRUMENT D TALK ONLY COUNTER DIO1 DIO8 DATA INPUT OUTPUT LINES DAV DATA VALID NRFD NOT READY FOR DATA NDAC NOT DATA ACCEPTED IFC INTERFACE CLEAR ATTENTION SRQ SERVICE REQUEST REN REMOTE ENABLE EOI END OR IDENTIFY 4415 22 Figure A 2 A typical GPIB system IEEE STD 488 GPIB System Concepts 494AP Programmers Interface control messages refer to Table 2 include the primary talk and listen addresses for instru ments on the bus addressed c
119. alue of a display data point The vertical scale is the same as illustrated for the CURVE query in Section 7 of this manual If the second number is not entered digital storage is asked for the value of the waveform at X the first number This makes the display data point correspond to a point in digital storage If the second number is sup plied in the POINT command the display data point may not correspond to any point in digital storage Macro Memory Used 5 bytes Examples POINT 500 150 center screen POI 1 25 screen bottom left POI 1000 225 screen top right Power up value 500 225 Interaction The SET response sent back to the instrument sets both the X and Y values of the display data point which may not correspond to any point in digital storage See Display Data Point Commands Interaction POINT display data point query Response to POINT query que LIO The first number is the X value of the display data point the second number is the Y value of the display data point Note that the query response may not match any point in digital storage if the Y value was set by a POINT command or if digital storage was updated after the display data point was acquired 8 1 Waveform Processing 494AP Programmers FIBIG find big command gt NUM This command seeks to acquire the largest signal peak with a point of greater value than NUM If a signal peak greater than NUM i
120. alyzer is faster Table 10 1 EXECUTION AND TRANSFER TIMES Command Time FREQ MFREQ 0 1 8 GHz 10 MHz div 800 ms 100 MHz step 10 MHz div 150 ms 0 1 8 GHz 1 MHz div 1 4 100 MHz step 1 MHz div 350 ms TUNE MTUNE 100 kHz step 100 kHz div 80 ms 100 Hz step 100 kHz div 60 ms 100 kHz step 100 Hz div 1 4 100 Hz step 100 Hz div 1 4 COUNT 1 Hz resolution 2 6 1 kHz resolution 1 25 s CNTCF 1 Hz resolution 2 8 1 kHz resolution 1 75 8 10 14 Table 10 1 Continued Command EXMXR and FRQRNG if transfer switch or pre selector LPF switch is changed SPAN to phase lock span boundary 10 kHz div to 1 MHz div IDENT ON 50 kHz 5 kHz o 500 Hz REFLVL RLMODE MINATT MAXPWR if RF attenuator is Switched CURVE CURVE Display Data Input Binary from number array ASCII as a string ASCII as numbers CURVE CURVE Display Data Output Binary input as strings ASCII input as a string ASCII input as numbers POINT X argument FIBIG LFTNXT RGTNXT FMAX FMIN SET command execution time SET response Display Data Output INIT CAL AUTO PEAK AUTO DSTORE displa DRECAL displa STORE settings RECALL settings MFBIG MLFTNXT MRGTNXT TEST HRAMPL LRAMPL Time Add 150 ms per switch 220 ms 32 5 ms 40 5 ms 156 ms Add 100 ms 100 ms 1 1 8 1 20 0 60 ms 3 4 3 0 14 3 56 ms 760 ms 100 ms signal separation in div 480 ms
121. alyzer makes a single sweep of the selected spectrum when the conditions determined by the TRIG command are met Refer to Programming Techniques in the Helps and Hints section later in this manual Instrument Control 494AP Programmers NOTE The Single Sweep mode should be used under most programming conditions see Programming Techniques in the Helps and Hints section later in this manual Macro Memory Used 1 byte Power up value OFF Interaction Any TRIG command cancels the single sweep mode SIGSWP single sweep query Response to SIGSWP query The response to the SET query is omitted if single sweep is not active see SET under Instrument Parame ters in the System Commands and Queries section of this manual TIME time div command 4 25 Instrument Control 494AP Programmers NUM 1 2 5 sequence in the range 20 0E 9 to 10 Numbers not in this sequence are rounded to the nearest step If the number selected is out of range execution error message 37 is issued AUTO The instrument is requested to select the fastest sweep allowed for calibrated response INC or DEC The sweep rate is changed 1 in the sequence if possible MAN The sweep is coupled to the MANUAL SCAN control so you can manually scan the spectrum As the control is turned the horizontal position of the crt beam and the instrument front end tuning are varied EXT The sweep is coupled to HORIZ TRIG EXT
122. am example shown in this manual The amended program would look like the following 80 2 1 90 srq then call srq hndl 100 Enable srq 110 Print 2 100 MHZ SPAN 1 MHZ REFLVL 20 DBM 120 End 130 Sub srq hndl 140 Integer status adr 150 Poll status adr z 3 2 160 Print status 170 If status 97 then print command error 180 If status 98 then print execution error 190 If status 99 then print internal error 200 If status 101 then print execution error warning 210 If status 102 then print internal error warning 220 End Whatever controller is used or statement is sent the actions shown in the syntax diagram below must be taken to get a message to the spectrum analyzer The UNL unlisten and UNT untalk messages are optional in the previous syntax diagram of bus traffic However one or both are sent by most controllers when they begin transmitting and end transmitting on the bus in order to guarantee a clear communications channel The controller sends the GPIB address you entered as part of the controllers GPIB I O statement The con troller either converts it to the spectrum analyzer listen address or expects to receive the listen address with the offset included i e 33 The controller then sends the device dependent message you inserted into the state ment and may finish by sending UNL and UNT If the controller does not assert REN remote enable automati cally for GPIB 1 0 you
123. and keep this in mind while preparing macros This maximum number of bytes used is included with the commands in this sec tion and there is also a table in the foldout pages at the back of this manual that lists all available spectrum analyzer commands and the bytes used by each WAVEFORM FINDING The spectrum analyzer has two sets of waveform finding commands two commands are described here and five are described in Section 6 of this manual The RGTNXT and LFTNXT waveform processing commands move the invisible display data point and the MRGTNXT and MLFTNXT marker commands move the Primary marker The display data point is specified and reported in screen units and the Primary marker is specified and reported in frequency and amplitude The two locations data point and marker and the two sets of commands are independent unless the display data point and the Primary marker are coupled with the MCPOIN command The DPMK command moves the display data point to the Primary marker location without coupling the two and MKDP moves the Primary marker to the horizontal loca tion of the display data point also without coupling the commands POINT display data point command GPs CL 9 NUM First NUM This is the X value of a display data point The horizontal scale is always the same as a full 1000 point waveform as explained under Display Data Point Commands Interaction later in this section Second NUM This is the Y v
124. and queries are in the Marker System section Frequency Frequency Span and Resolution Vertical Display and Reference Level Sweep Control Digital Storage Display Control General Purpose Marker System Control Marker Positioning Marker Finding The mnemonics codes in Table 4 1 correspond to the instrument names for the front panel pushbuttons and controls and related functions Table 4 1 FRONT PANEL COMMANDS AND QUERIES Name Mnemonic Frequenc FREQ ENTRY FREQ CENTER MARKER FREQUENCY TUNE TUNE CF TMODE 15 LO FIRST 2ND LO SECOND Tracking Generator Mode TGMODE Sideband Analyzer Mode SAMODE Disable Tuning Corrections DISCOR A Band and V Band FRQRNG STEP ENTRY STEP STEP MSTEP STEP PSTEP COUNT COUNT COUNT RESOLN CRES Count Cr CNTCF FREQ START STOP STSTOP AF DELFR Degauss DEGAUS EXT MIXER b EXMXR IMPEDANCE IMPED Frequency Span and Resolution FREQUENCY SPAN DIV and SPAN SPAN DIV ENTRY ZERO SPAN ZEROSP MAX SPAN MXSPN RESOLUTION BANDWIDTH RESBW AUTO RESOLN ARES IDENT IDENT Table 4 1 cont Name Mnemonic Vertical Display and Reference Level 10dB DIV 2dB DIV LIN VRTDSP dB DIV ENTRY REFERENCE LEVEL and REFLVL REF LEVEL ENTRY REF LEVEL UNITS CAL RLUNIT and ROFSET Enable Calibration Factors ENCAL FINE FINE MIN NOISE MIN DISTORTION RLMODE Reduced Gain Mode RGMODE MANUAL PEAK AUTO PEAK MIN RF ATTEN dB MINATT MAXPWR a
125. at any message sent or received when the ATN line is asserted low is an interface con trol message Any message data bytes sent or received when the ATN line is unasserted high is a device dependent message GPIB SIGNAL LINE DEFINITIONS Figure A 2 shows how the sixteen active signal lines on the GPIB are functionally divided into three com ponent buses an eight line data bus a three line data byte transfer control handshake bus and a five line general interface management bus The data bus contains eight bi directional signal lines 0101 through 0108 Information in the form of data bytes 15 transferred over this bus A handshake timing sequence between the enabled talker and the enabled listeners on the three line data transfer control bus transfers one data byte eight bits at a time These data bytes are sent and received in a byte serial bit parallel fashion Since the handshake sequence is an asynchronous operation no clock signal on the bus the data transfer rate is only as fast as the slowest instrument involved in a data byte transfer A talker cannot place data bytes on the bus faster than the slowest listener can accept them Figure A 4 illustrates the flow of data bytes on the bus when a typical controller sends ASCII data to an assigned listener The first data byte decimal 44 enables an instrument at address 12 as a primary listener The second data byte decimal 108 is optional for example enabling
126. at cannot be used within macros are noted Prepare your macros using a language such as BASIC and a controller Once the macro is stored in the spectrum analyzer memory it can be run at any time without the further use of a controller We recommend that a copy of all macros be kept for ease in reconstruct ing a macro if it is lost Any stored macros will be lost if the battery powered memory is interrupted as when the battery is removed for long term storage There are two harmonic test macros in the pullout pages at the back of this manual that were prepared to be stored in the spectrum analyzer and used without the need of a controller 10 1 Helps and Hints 494AP Programmers DATA ACQUISITION When the spectrum analyzer is executing commands under program control there are two programs running not just one One program is running in the controller and a second in the spectrum analyzer The key to success is synchronizing the execution of the two programs In addition the two programs must be synchronized with the data acquisition event in this case the sweep Synchronizing Controller and Spectrum Analyzer Programs must run in the controller at the same time that the spectrum analyzer acts on messages that come over the GPIB This is all done within the spectrum analyzer by the way it buffers and executes messages When the spectrum analyzer receives a message it waits until the end of the message to begin acting
127. ate 1 for busy 0 for not busy Error codes however are accumulated until read and are reported in numerical order While you can recover only one status byte you may recover more than one code in the ERR query response indicating more 10 13 Helps and Hints 494AP Programmers than one abnormal condition occurred The status byte is cleared by a serial poll of that instrument Error codes are cleared by reading them with the ERR query Reading the status byte does not clear the error codes and vice versa DCL and SDC if addressed clear both the status byte and error codes EXECUTION AND TRANSFER TIMES The spectrum analyzer firmware typically takes 10 to 25 ms to execute commands received over the bus refer to Table 10 1 This is the time the spectrum analyzer is busy following receipt of the end of message terminator EOI or LF depending on the switch Execution time for some commands stretches beyond 25 ms however because of interaction between the firmware and hardware or a wait to allow hardware response If the spectrum analyzer is busy any command will have to wait until the hardware is not busy e g if a signal count is being done any command other than COUNT will have to wait Because of the way the spectrum analyzer handles output it is free after it loads an output buffer The addi tional time for the transfer for CURVE CURVE and SET is related to the listener for cases where the spec trum an
128. ational power cords Tektronix Options A1 A2 A3 and A5 are approved only for the country of use and are not included in the CSA certification Refer cord and connector changes to qualified ser vice personnel For detailed information on power cords and connec tors see the Maintenance section in the Service Manual Volume 1 Use the Proper Fuse To avoid fire hazard or equipment damage use only the fuse of correct type voltage rating and current rating for your product as specified in the Replaceable Electri cal Parts list in Volume 2 of the Service Manual Refer fuse replacement to qualified service personnel 494AP Programmers OPERATIONAL PRECAUTIONS Do Not Operate in Explosive Atmospheres To avoid explosion do not operate this product in an explosive atmosphere unless it has been specifically certified for such operation Do Not Remove Covers or Panels To avoid personal injury do not remove the product covers or panels unless you are qualified to do so Do not operate the product without the covers and panels properly installed Dangerous voltages exist at several points in this product To avoid personal injury do not touch exposed connections and components while power is on REFER ALL SERVICING TO QUALIFIED SERVICE PERSONNEL 494AP Programmers analyzer REF LEVEL CENTER FREQUENCY SPANIDIV MKR LEVEL MARKER FREQUENCY Cre vom GRAT ILLUM F gt CENTER READ A
129. aveform is recalled from the memory specified by NUM 0 8 and put in the A waveform display If AVIEW is ON and BVIEW and BMINA are OFF the readout associated with a recalled A waveform is displayed B A waveform is recalled from the memory specified by NUM 0 8 and put in the B waveform display If BVIEW or BMINA is ON the readout associ ated with a recalled B waveform is displayed if in single Sweep NOTE The contents of B will be overwritten on the next sweep unless SINGLE SWEEP is ON Macro Memory Used 3 bytes Examples DRECAL A 4 DRE B 2 Range 0 to 8 Interaction DRECAL turns SAVEA ON The B waveform display will be overwritten if the instrument is not in the single sweep mode If you try to recall a waveform from an empty memory location execution error message 62 will be issued There is no DRECAL query Instrument Control 494AP Programmers MXHLD max hold command ON Digital storage holds the maximum value obtained for each point in both the A and B waveforms a point is updated only if the new value is greater than the current value The A waveform is not affected if SAVEA is on OFF The B waveform is continuously updated the waveform is updated only if SAVEA is OFF Macro Memory Used 2 bytes Power up value OFF MXHLD max hold query Response to MXHLD query KNOB The PEAK AVERAGE control is under local control so you can set the cursor lev
130. ber of event codes If the number requested is out of range maximum number of 39 execution error mes sage 46 will be issued Macro Memory Used 2 bytes Power up value 0 NUMEV number of events query Response to NUMEV query NUMEV returns the current value for NUMEV EVQTY event quantity query COLO Response to EVQTY query NR1 specifies the number of events that will be returned in the next ALLEV If the NUMEV setting is 0 and EVQTY is not executed ALLEV returns an unspecified number of events There is no EVQTY command System Commands and Queries 494AP Programmers TEST internal test query Crest This query checks the system ROM and RAM Response to TEST query The TEST query response consists of two decimal numbers that indicate if a ROM or RAM IC was found to be defective These numbers must be translated to their binary equivalents to determine the ROM and RAM loca tions If all ROM and RAM are good the TEST query response wil be ROM 0 RAM 0 After the binary numbers are determined put them into the conversion chart in Figure 9 1 to identify the IC number Then use Table 9 3 to find the correct circuit number and circuit board The following example shows how to use the conversion chart and Table 9 3 If any ROM or RAM ICs are indicated to be bad refer this information to qualified service personnel Example Print A TEST Input A R Print R
131. brated the UNCAL light will come on e With the TIME AUTO command the sweep speed may vary as each band is swept Any time division value refers to a division of the sweep that gathered the data not to a division of the compressed display e f the sweep is not in TRIG FRERUN the triggering conditions selected will be used for only the first lowest frequency sweep of the sweep needed to do one complete multiband sweep After this sweep is triggered the remaining sweeps will be done in the Free Run mode Similarly once a single sweep is started with the SIGSWP command the number of sweeps needed to form a complete display will occur If a multiband sweep is interrupted by the SIGSWP command or GET command the next sweep will be the lowest frequency sweep Helps and Hints 494AP Programmers TIME MAN or EXT cannot be used when sweeping a multiband range e The COUNT command cannot be used in the Multi band Sweep mode Auto peaking will be done as usual in a 2 division window centered on the center or marker frequency If this range covers more than one band peaking will be done in all bands covered If there is at least one signal within a band or portion of a band the peak value of the frequency window that contains the largest signal will be updated Exiting Multiband Sweep Multiband sweep may be exited in several ways e Using the FREQ command to enter a frequency e Recalling a setting with RECAL w
132. buffer Line 140 Displays three lines normal top line LINE 3 from line of the macro readout buffer at the third line on the screen and LINE 7 from line 7 of the macro readout buffer at the seventh line on the screen Line 160 Displays three lines normal marker line at the second line on the screen LINE 7 from line 7 of the macro readout buffer at the seventh line on the screen and LINE 8 from line 8 of the macro readout buffer at the eighth line on the screen Macro Memory Used 4 bytes Range NUM is 1 to 16 Power up value TOP MARKER and BOTTOM Interaction The TEXT mode must be in SHORT normal 3 line mode for DSLINE to have any effect on the readout DSLINE display line query Response to DSLINE query Gut rang Com pu O MRDO macro readout query Os NUM The line selected by NUM will be returned from the readout buffer that the PRINT command uses If MRDO is sent without an argument or NUM is greater than 16 all 16 lines of the readout buffer will be returned Response to MRDO query PRINT print number or string command The PRINT command syntax diagram is on the fol lowing page The following is a simplified representation of the PRINT command syntax diagram starting location number or string The PRINT command prints a number and a string of up to 29 characters or a string of up to 40 characters The first argument set
133. can set it with an earlier control statement The spectrum analyzer does not balk if REN is not set unless you send commands that change front panel settings or data in digital storage That leaves the most important part up to you what goes in the controller statement as a device dependent message The spectrum analyzer control mnemonics are collected for quick reference on a Program Summary fol dout chart at the back of this manual For details on how to state each command correctly and the instrument response turn to the command descriptions that begin in Section 4 The detailed descriptions are arranged by function refer to the foldout chart at the back of this manual for page numbers The spectrum analyzer executes the message when it sees the message terminator either EOI or LF Mes sage syntax and command execution are given fuller treatment in Section 2 of this manual Querying Programmable Controls The spectrum analyzer returns the state of program mable controls when queried This takes two steps 1 Query the spectrum analyzer The query takes the form of the mnemonic for a function name followed by a question mark 2 Read the response A GPIB INPUT statement does the job in the case of most controllers The response will be returned as a character string with or without the applicable header depending on whether the HDR command is ON or OFF see the Header informa tion in Section 2 of this manual For examp
134. care of other tasks while the spectrum analyzer is acquiring data In such cases the controller can enable the spectrum analyzer end of sweep SRQ to synchronize data acquisition with the sweep The following example just shifts the WAIT from the spectrum analyzer program to the 4041 BASIC program to exercise the SRQ It could be modified however to busy the controller with some other task using the SRQ subroutine to test the status byte and perform input when end of sweep status is detected 80 2 1 ADDRESS OF SPECTRUM ANALYZER 100 Dim p 5 2 110 srq then call srq hndl 120 Enable srq 130 Print z SIGSWP EOS ON 140 Fori 1to5 150 Print z FREQ si GHZ SIGSWP 160 Wait 170 Print z FMAX POINT 180 Input z p i 1 p i 2 190 Next i 200 End 300 Sub srq hndl 310 Integer status adr 320 Poll status adr z 330 Resume 340 End With no WAIT command following SIGSWP in line 150 the spectrum analyzer is ready to buffer another message But the controller does not send it immedi ately because of the WAIT statement in line 160 The SRQ that the spectrum analyzer asserts at the end of its sweep which was enabled in line 130 triggers the con troller to perform a serial poll lines 300 through 340 and then send the message in line 170 INPUT An SRQ Alternative An INPUT statement in the right place is an alterna tive to waiting for an end of sweep SRQ This tactic takes advantage of a spectrum analyzer output f
135. counter mode Macro Memory Used 2 bytes Power up value OFF Interaction If a marker s is on a non saved trace COUNT will count at the marker COUNT will count at center screen if MKR is OFF If MXSPN is ON counting will occur at the maximum span dot position rather than center screen Signals cannot be counted on a trace saved with SAVEA or with STORE and RECALL 4 8 COUNT counter query COLO Response to COUNT query The number returned in this response is the result of the last count regardless of whether COUNT is ON or OFF If a signal count has not been made 0 will be returned The number will not be returned with the SET query response CRES counter resolution command cres 8 NUM NUM The proper decade of counter resolution is selected for use Numbers that are not powers of ten will be set to the next lower power of ten up to a maximum of 1 GHz resolution If the number is out of range execu tion error message 30 will be issued Marker Memory Used 4 bytes Range 0 1 GHz Power up value 1 Hz CRES counter resolution query Response to CRES query ARA Com 9 CNTCF count to center frequency command A count of the signal is taken then this signal count result is transferred to the center frequency This tunes the spectrum analyzer to the signal counted Accuracy is limited by the count resolution in use when the signal count is done Marker
136. cro readout buffer PRINT 4 2 N O SIGNA L F OUND ENDI DONE Done with macro EMAC End macro entry OUTPUT FOR HARMONIC MACRO TEST displayed on the CRT of the 49X HARMONIC TEST FUNDAMENTAL FREQUENCY 100 000 238MHZ HARM it l 2 3 4 5 6 7 NO SIGNAL 8 9 Hp LEVEL 30 ODBM 35 0DBM 36 2DBM 42 0DBM 54 3DBM 56 0DBM 72 4DBM 79 9DBM 87 ODBM AMPLITUDE 10 0DBM PASS FAIL HARMONIC TEST MACRO MACRO PREPARATION The following program shows the 4041 Data statements necessary for the PASS FAIL HARMONIC TEST program This macro will display TEST PASSED on line 4 of the crt if the fundamental s 1st harmonic is less than 60 dBc from the fundamental s amplitude If it is not TEST FAILED will be displayed on line 4 of the crt This macro will use less than 5 of the total available 8K bytes of memory set aside for macro storage 10 Z 1 20 MACRO NUMBERO HARMONIC PASS FAIL test 30 Data stmac 0 HARMONIC PASS FAIL 40 Data marker single sweep mfbig clear 4 dsline top 4 bottom 50 Data if signal mcen step primar marker delta pstep 60 Data sweep thrhld 60 mfbig if nosig print 4 10 test passed 70 Data else print 4 12 TEST FAILED 80 Data endi mstep thrhld auto else 90 Data print4 2NO SIGNAL FOUN D endi marker off done emac 100 MACRO NUMBER 1 HARMONIC TEST 110 Data stmac 1 HARMONIC TEST 120 Data marker single rdout normal clear 130 Data sweep mfbig if
137. ctor drivers because of the high speed opera tion of the instrument Introduction to GPIB Operation 494AP Programmers 15 V MAX OUTPUT ER CORD PROTECTIVE GROUNDING EARTH GROUND DO NOT REMOVE LIFIED PERSONNEL IEEE STD 488 PORT SH1 AH1 T5 L3 SR1 RL1 PP1 DC1 DT1 CO E2 Figure 1 5 The rear panel IEEE STD 488 PORT GPIB The GPIB is a flexible system that works either in a star or linear pattern shown in Figure 1 6 Up to 15 dev ices can be connected at one time To maintain bus electrical characteristics no more than one 2 meter cable should be connected for each device one for the controller one for the spectrum analyzer and so on and at least two thirds of the devices connected must be on Appendix A details the IEEE STD 488 GPIB System Concepts An internal switch change causes the spectrum analyzer to assert SRQ when power is first applied This requires immediate action by some controllers so is not recommended for these controllers Because changing the switch requires that the cover be removed refer this task to qualified service personnel The instrument start up procedure is provided in both the Operators Manual and the Operators Handbook Refer to those books for instructions on how to begin operating the instrument Refer to your local Tektronix Field Office or representative for Manual ordering infor mation The initial power on setting of all programmable func tions is
138. d from the resolu tion filter in use Note that this is not the same algorithm as the one used by the data point related commands In particular the data point algorithm looks for a particular width while the marker related algorithm looks only for a minimum width Note also that if the span is wide in com parison with the resolution bandwidth there may be no difference between SPURS and CW When PULSE is chosen if two candidate signals are within two minor divisions 0 4 of a major division they are assumed to be either time related lines or spectral lines belonging to the same pulse This extends to multiple lines in a group of such lines the highest amplitude line will be identified as the center of the signal Another difference between the display point com mands and the marker commands is the output units The POI query reports in screen units 1 1000 horizon tally and 25 225 vertically The marker queries report the actual frequency and amplitude of the marker Two other factors affect the results The first of these is separation With any of the signal processing com mands there must be at least a 3 dB notch between two signals in order for them to be individually recog nized The second factor is noise Because noise is ran dom noise peaks may appear to be small signals Whether or not these peaks are detected may be con trolled by using a threshold with the signal processing commands This is discussed in the fo
139. dependent of each other The T Talker and TE Talker Extended functions provide an instrument and its secondary devices if any with the capability to send device dependent data over the GPIB or in case of a controller the capability to send device dependent program data over the GPIB IEEE STD 488 GPIB System Concepts 494AP Programmers The Talker T function is a normal function for a talker and uses only a one byte primary address code called MTA My Talk Address The Talker Extended TE func tion requires a two byte address code an MTA code fol lowed by the second byte called MSA My Secondary Address Only one instrument in the GPIB system can be in the active talker state at any given time A non controller commences talking when ATN is released and continues its talker status until an Interface Clear IFC message occurs or an Untalk UNT command is received from the controller in charge The instrument will stop talking and listen any time that the controller in charge asserts ATN One or more instruments on the bus can be pro grammed for the L Listener function by use of their specific primary listen address called MLA Some of the instruments interfaced to the bus may be programmed for the LE Listener Extended function if implemented The LE function requires a two byte address code No L or LE function is active during the time that ATN is asserted All talker and listener functions must respond
140. do not change when switching from remote to local control except as necessary to match the settings of front panel controls for TIME DIV MIN RF ATTEN dB and PEAK AVERAGE The spectrum analyzer flashes the instrument name firmware version number the GPIB address and the macro status message on the crt when RESET TO LOCAL is pressed If there is no macro running the mes sage will be MACRO OFF where indicates the menu location of the last macro that was run If there is a macro running the message will be MACRO RUN where indicates the menu location of the macro that is running If there is a macro in process but stopped the message will be MACRO STOP where indicates the menu location of the macro that is stopped If a macro is being stored in memory the message will be MACRO STORE where indicates the menu location where the macro is being stored lt Blue SHIFT gt PLOT Press this pushbutton when the spectrum analyzer is in the talk only mode for the instrument to send the appropriate commands over the GPIB to a plotter which must be in the listen only mode connected to the bus see the TALK ONLY LISTEN ONLY switch descriptions later in this section The spectrum analyzer display waveform marker s graticule and crt readout can be recreated on a TEKTRONIX 4662 Option 01 or 4662 Option 31 Interactive Digital Plotter or a 4663 in the 4662 emulation mode or a Hewlett Packard HP7470A or HP7475A HP7580
141. e that covers more than one band the spectrum analyzer first determines the bands involved and calculates the center frequency and span needed in each band to cover the desired range Then the microcomputer successively sets the instrument and performs one sweep in each band The digital data is collected in the B digital display This data is then compressed to cover the appropriate portion of the screen and is displayed in the A storage display During multiband sweep operation MULTIBD is displayed at the bottom center of the screen If the start frequency is less than 3 GHz and the stop frequency is greater than 7 1 GHz the 3 GHz 7 1 GHz band is not used Instrument Operating Differences When In the Multi band Sweep Mode Because of the method used to obtain a multiband sweep certain instrument functions must be locked out and others will operate differently from normal To remind you of these differences multi band execution error message 150 is issued when you enter the mode and message 151 is issued when you exit the mode Following are the functional operating differences that are present when in the Multiband Sweep mode e To allow data collection in the B display of digital storage while AVIEW is ON the storage must be set with AVIEW ON and BVIEW and BMINA OFF These settings are changed automatically when the Multi band Sweep mode is entered and cannot be changed while in the mode The existing settings are resto
142. e GPIB For example 4041 BASIC contains optional OPEN and SET DRIVER state ments that set GPIB communications parameters These statements are not included in the program examples because the default parameter values are suitable for simple programs such as the examples The statements may be helpful in writing programs involving multiple 1 channels such as tape files or other GPIB controller instruments Refer to the manual of the controller you are using for the statements needed in your application In these examples the spectrum analyzer s primary address is assumed to be 1 See Section 1 of this manual for instructions on how to set the GPIB address switches Some of the lines in the examples extend beyond the column width limitations When this happens the line is broken where a natural space occurs and the remainder of the line is indented on the immediately following line Because of this natural space a space must be added between the two example lines when joining them to form one program line PROGRAMMING TECHNIQUES Signal Processing The instrument should be in the Single Sweep mode and not be sweeping during any of the signal processing commands or queries The signal processing commands are HRAMPL LRAMPL MFBIG MLFTNX PKFIND MMAX MMIN MRGTNX MVLFDB MVRTDB CURVE WAVFRM DPRE DCOPY FIBIG LFTNXT RGTNXT FMAX and FMIN Wrong Way The following is an unsuccessful com mand line to try to center a
143. e asserted to interpret the status of all selected instruments To conclude the parallel poll the controller releases EOI and then The instrument s do not need to be reconfigured for each subsequent parallel poll The PPU Parallel Poll Unconfigure command will clear all device configurations and prevent them from responding to future polls The PPD Parallel Poll Disable command accomplishes essentially the same thing except that the PP function remains in the configured state PPU is a universal command all instruments while PPD is used with PPC and becomes an addressed command only those devices selected with PPC will accept PPD NOTES e To assure correct and expected results during signal processing use the Single Sweep triggering mode while programming The signal processing com mands are HRAMPL LRAMPL MFBIG MLFTNX PKFIND MMAX MRGTNX MVLFDB MVRTDB CURVE WAVFRM DPRE DCOPY FIBIG LFTNXT RGTNXT FMAX and FMIN e Only the first three letters of a mnemonic are required e g ARE for AREs except all of the letters of the units arguments for REFLVL and MAXPWR must be entered e Form a query by adding a question mark to the header of a Display Data 1 0 Marker System Macro or Front Panel header AREs unless no query is indicated POInt is the only Waveform Processing query e The header will be returned with query responses with HDR ON or the header will not be returned with HDR OFF
144. e the search routine to find signals close to the noise floor USING REPEAT FOR SIGNAL TRACKING AND SEARCHES NOTE The REPEAT command cannot be used within customized macros because it causes a loop condition Therefore the examples shown for this discussion cannot be used within macros The REPEAT command adds another dimension to spectrum analyzer messages the number of times a loop through a string of commands or queries Several uses are suggested here Spectrum Search Using Repeat The spectrum analyzer can perform a signal search by executing a loop in a single message and buffering the results without controller interaction The controller can later turn its attention again to the spectrum analyzer and input the results The following routine works on a waveform in digital storage that is not updated during processing 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 SPECTRUM SEARCH 110 Print z POINT 0 120 Print z RGTNXT POINT REPEAT 20 130 ve he e ee e e e e e de dede en n 140 INSERT ANY OTHER TASKS 150 n eh 300 Dim p 20 2 310 Input z p Line 120 The spectrum analyzer buffers the query responses as it executes the loop Line 310 Inputs the signal points as a string del imited by semicolons The number of query responses that can be buffered depends on the query and the message sent to the spec trum analyzer Messages and responses share buffer space Long messages will leave less
145. e they do not meet the minimum bandwidth criteria If Pulse was selected signals A B D E F and G would be identified Signal C would be skipped because it is within 2 minor divisions from sig nal B The PULSE algorithm will think signal C is a part of signal B If Spurs was selected all signals would be identified Macro Memory Used 2 bytes Power up status CW Interaction The STYPE command affects the marker finding commands MFBIG MLFTNX MRGTNX HRAMPL and LRAMPL STYPE signal type query STYPE 2 Response to STYPE query LEVEL REF 20DBM CEN MKR 42 4DBM MKR J 10DB VERT RF DISPLAY ATTEN FREQUENCY 800 8 GHZ S KHZ DBM 1 800 0006H7 IN NU Au AN UNE SM FREQ REF VIDEO RESOLUTION RANGE OSC FILTER BANDWIDTH SPAN DIV TOY jt 5557 03 Figure 5 3 Signal finding example 5 16 Marker System 494AP Programmers REQUENCY 800 0006H7 800GH7 PC EE I T i 1808 0 1 8 10 2 RF FREQ REF VIDEO RESOLUTION ATTEN RANGE OSC FILTER BANDWIDTH Figure 5 4 Signal finding example i HI IM Tp 1008 ATTEN Hi RU RANGE osc FIL 6195 03 Figure 5 5 Signal f
146. eature if the analyzer has no output when it receives its talk address it outputs a byte with all bits set to one as soon as it is not busy 80 2 1 ADDRESS OF SPECTRUM ANALYZER 100 Dim p 5 2 110 Print z SIGSWP 120 Fori 1to5 130 Print z FREQ i GHZ SIGSWP WAIT 140 Input z d 150 Print z fmax poi 160 Input 2 1 2 170 Nexti 180 End 10 4 Here the WAIT is put back into the spectrum analyzer message and the INPUT statement in line 140 stalls the controller while the spectrum analyzer makes a sweep d serves the purpose of a dummy string the data is not input until line 160 BINARY WAVEFORM TRANSFER These examples cannot be used as presented here in customized macros because they contain the CURVE and WFMPRE commands Selecting binary rather than ASCII coded decimal speeds up waveform transfers Neither the controller nor the spectrum analyzer has to perform a conversion between binary and ASCII The difference is evident in the times for both kinds of transfer listed in this section under Execution Times Table 10 1 The gains possible by using binary are not hard to achieve Here s how Getting Spectrum Analyzer Binary Curve Output The spectrum analyzer encloses binary waveform data values in the binary block format For details see the syntax diagrams in Sections 4 and 7 For a 4041 routine that handles block binary enter the following 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 500
147. ected NEXT command not expected Index out of range DISBUF INDEX or VAR INDEX FOR index is already used Missing DONE or RETURN or GOTO ERROR EVENT System Commands and Queries 494AP Programmers Table 9 4 Continued Meaning 140 141 143 150 151 152 204 205 204 556 558 556 559 Multiband Execution Errors Function either not available or cannot be changed when in multiband sweep Frequency out of range because instrument is in multiband sweep Multiband sweep cannot be started in external or manual sweep Multiband Execution Warnings Multiband sweep started Multiband sweep stopped Start frequency changed Multiband sweep started Multiband sweep stopped Start frequency changed to 1 7 GHz because of using internal mixer 9 17 Section 10 494AP Programmers HELPS AND HINTS This section covers some techniques for program ming the spectrum analyzer This information will speed your progress in putting the spectrum analyzer to work solving your measurement problems Notes on the Program Examples Many combinations of languages and controllers may be used for programming the spectrum analyzer over the GPIB The examples in this manual are given in the BASIC language specifically in the version of BASIC used by the Tektronix 4041 System Controller Other ver sions of BASIC will probably have similar syntax Some ontrollers may require additional statements to set up data transfer over th
148. ed 4 bytes Examples M2ASGN MRGTNX M2A MVR 100 M2ASGN MVLFDB 80DB Power up value The assignment is stored in memory The power up value is the marker function that was assigned when the power to the instrument was last turned off If no assignment has ever been made MLFTNX is assigned Interaction The M2ASGN command affects only the command that will be executed when the front panel ASSIGN 2 pushbutton is pressed while the instrument is under local control M2ASQN assign marker pushbutton 2 query 5 4 Response to M2ASGN query CORO o i HERD NSELVL noise level normalization command NSELvL The Primary marker amplitude readout normalizes to the resolution bandwidth and changes the units of the marker amplitude readout from units to units Hz This command assumes the Primary marker is on noise not on a signal If the marker is on a signal the marker amplitude readout is incorrect ON The normalization is turned on OFF The normalization is turned off Macro Memory Used 2 bytes Power up value OFF Interaction The marker amplitude readout is in reference level units Hz If MARKER is OFF NSELVL sets MARKER to SINGLE NSELVL noise level normalization query NSELVL Response to NSELVL query The noise level at the position of the Primary marker is returned regardless of whether NSELVL is ON or OFF The number is not returned with
149. een signal peak MFBIG move the Primary marker to 5 9 Marker System 494AP Programmers the next signal peak to the left or the right MLFTNX or set the Primary marker to the largest or smal lest vertical value in digital storage MMAX or MMIN set the Primary marker to the largest vertical value in digital storage that is above threshold PKFIND set the Pri mary marker to the largest vertical value in digital storage that is above threshold and tune the marker fre quency to center screen PKCEN set the threshold for the Primary marker signal find commands MLFTNX MRGTNX MFBIG HRAMPL LRAMPL SGTRAK BWMODE and PKFIND THRHLD move the Primary marker to the left and down or up or to the right and down or up from the present position MVLFDB or MVRTDB set the signal type STYPE and assert SRQ when the signal identification routine cannot find the requested signal SGERR HRAMPL Next higher amplitude command The HRAMPL command moves the Primary marker to the next higher amplitude signal on the display If the marker is on the highest signal on the display or if no signal is found the marker does not move Macro Memory Used 1 byte Interaction If SGERR is ON marker execution warning message 130 is issued if a signal is not found If MARKER is OFF HRAMPL sets MARKER to SINGLE The criteria for a signal are set by the THRHLD and STYPE commands HRAMPL next higher amplitude query
150. el which is shown by a line across the crt Above the line peak values are stored as each point is updated below the line averaged values are stored PEAK The line position on the crt is not affected The peak value digitized at each point is used to update digital storage regardless of the cursor position last set by KNOB This is the same as setting the cursor to its lowest minimum position AVG The line position on the crt is not affected Average values are used to update the waveforms regardless of the cursor position last set by KNOB PEAK AVG is the same as if the cursor is set to its highest maximum position 4 29 Instrument Control 494AP Programmers NUM 0 KNOB 1 PEAK 2 AVG Macro Memory Used 2 bytes Interaction Averaging can reduce the value in digi tal storage for signals with very narrow response or pulsed signals Power up value KNOB CRSOR peak average cursor query Response to CRSOR query 4 30 Instrument Control 494AP Programmers DISPLAY CONTROL These commands control the instrument crt display functions to display the readout REDOUT light the graticule GRAT and eliminate the baseline trace CLIP FREQUENCY gt RESOLUTION SPAN DIV BANDWIDTH MIXER EKT MIXER PRESEL 5559 11 Figure 4 6 Front panel Display Control commands REDOUT readout command Power up value ON REDOUT readout query COO Response to REDOUT query
151. er the GPIB with the ATN line asserted are interpreted as system control information Asserting ATN directly at any moment is an asynchronous operation with respect to the bus and may cause loss of data if a handshake cycle is in progress To prevent loss of data a controller can take control synchronously that is it can monitor the Transfer Bus and only assert ATN when DAV is unasserted false Passing Control As a controller in charge the system controller pro gram may relinquish contro to any other instrument in the system capable of acting as a controller The con troller in charge first addresses the other controller as a A 10 talker and then sends the TCT Take Control command The other controller then becomes the controller in charge when ATN is released Performing a Serial Poll The controller in charge may conduct a serial poll at any time whether or not an instrument on the bus has asserted the SRQ line Most but not all instruments have the Service Request SR function To perform a serial poll the controller first asserts and issues the Untalk UNT and Unlisten UNL commands The controller then sends the Serial Poll Enable SPE command followed by the talk address of the first instrument to be polled The controller then releases ATN and the addressed talker responds by sending its status byte over the bus If the addressed talker has requested service it must assert bit seven of the statu
152. es LONG The readout is switched to the 16 line mode without a spectrum display RDOUT commands wvill fill the top line first then fill successive lines until all lines have characters When all 16 lines are full of characters the entire screen scrolls up Send TEXT LONG again to clear the page of the readout and begin sending charac ters to the top line again MACRO The readout is switched to the 16 line mode without a spectrum display and the macro readout buffer is displayed The PRINT command is used to display data into the macro readout buffer The CLEAR command can be used to clear the macro readout buffer Macro Memory Used 2 bytes Power up value SHORT Interaction If the crt readout is not in the NOR MAL mode when TEXT is executed the readout will be cleared this could be used as a page command to clear the screen for new text RDOUT NORMAL restores normal spectrum analyzer readout TEXT text mode query Response to TEXT query UPRDO upper readout query COLO Display Data and Crt Readout 1 0 494AP Programmers Response to UPRDO query 40 CHARACTER STRING CHARACTER Characters are from the upper row of regular crt readout Blanks are transmitted as spaces Regular readout that would be displayed if GPIB did not have control whether visible on the screen or not is the readout returned by the query not a message sent to the instrument by RDOUT With AVIEW and SA
153. es None N A None N A None N A None N A None 1 byte On Off Number On Off Number 2 bytes Arguments are divided into the following four categories None No arguments are required On Off The arguments ON or num 1 or OFF or num 2 are required Number Number s argument required terminator optional Special Specific command arguments character strings or any combination of these categories are required command cannot be used within macro This command can only be used within a macro it cannot be used outside a macro Page 9 10 4 14 4 27 4 28 4 28 5 10 4 18 4 9 4 29 7 4 4 10 9 11 9 11 9 10 9 11 6 3 4 10 8 2 4 20 4 5 QUICK REFERENCE TO COMMANDS AND QUERIES Continued Mnemonic RLUNIT ROFSET RQS RUN RVALID SAMODE SAVEA SECQND pn SGERR SGTRAK SIGSWP SPAN SSR b STATUS BYTE STEP STMAC STNUM STORE STSTOP STYPE SUBT SWEEP TEST TEXT TGMODE THRHLD TIME TMODE TOPSIG TRIG TUNE UPRDO VAR VIDFLT VRTDSP WAIT WARMSG WAVFRM WFMPRE ZEROSP ZETIME ZOOM b b Query Available Macro Memory Used Special On Off On Off Number None On Off 2 bytes On Off 2 bytes Number 6 bytes None N A On Off 2 bytes Special 2 bytes None 1 byte Special 5 bytes Number 2 bytes N A N A Special 6 bytes Special N A Number
154. f it is not macro execution error message 178 is issued There is no RETURN query GOSUB go to LABELed subroutine command NUM Macro control is transferred to the LABELed subroutine The macro will return to the next command following the GOSUB when the macro finds a RETURN statement The following example illustrates the use of the GOSUB command THIS PROGRAM WILL DELETE ANY PRO GRAM STORED IN MACRO LOCATION 7 70 Z 1 ADDRESS OF SPECTRUM ANALYZER 80 Print z KILL 7 90 Print z STMAC 7 GOSUB TEST 100 Print z FREQ 100M 110 Print z GOSUB 1 120 Print 2 200M 130 Print 4z GOSUB 1 140 Print z FREQ 300M 150 Print z GOSUB 1 160 Print z DONE 170 Print z LABEL 1 180 Print z SWEEP MFBIG PAUSE 5 190 Print z RETURN 200 Print z EMAC Lines 100 and 110 Sets the center frequency to 100 MHz and sends macro control to LABEL 1 Lines 120 and 130 Sets the center frequency to 200 MHz and sends macro control again to LABEL 1 Lines 140 and 150 Sets the center frequency to 300 MHz and sends macro control again to LABEL 1 Line 180 Takes a sweep moves the marker to the maximum signal and waits 5 seconds before the next macro command is executed 6 7 Macros 494AP Programmers Line 190 The macro returns to the line following the last GOSUB When the macro goes up to line 160 the macro is through running If there are more than 20 nested GOSU
155. frequency closest to that already in use that encom passes the frequency setting that responds to the FREQ command In option 07 instruments when using 75 Q input if the requested frequency range is outside the allowable limits if you send anything except FRQRNG 1 execution error message 102 is issued FRQRNG frequency range query FRQRNG gt Response to FRQRNG query CDA C STEP step size command The STEP command sets the frequency step size used by the MSTEP and PSTEP commands PRIMAR Sets the step size to the primary marker frequency SECOND Sets the step size of the secondary marker frequency DELTA Sets the step size to the absolute value of the difference in frequency between the primary and secondary markers CF Sets the step size to the absolute value of the center frequency NUM Sets the step size to the frequency input Macro Memory Used 6 bytes Examples STE DEL STE PRIMAR STEP SEC STE 20 KHZ STEP 100 MHZ Range Set STEP anywhere within the internal mixer band range In the waveguide mixer bands STEP can be used within a single band only The largest acceptable value is 155 GHz the width of band 12 If a larger value is entered STEP will be set to 155 GHz Power up value See Interaction that follows Interaction STEP DELTA and STEP SECOND cause marker execution error message 123 to be issued if MARKER is not set to DELTA If the freque
156. g the front panel push buttons for these three settings 1 Press the lt blue SHIFT gt FREQ 1 0 0 MHZ push buttons to center the CAL OUT signal 2 Span down to look more closely at the signal by pressing the blue SHIFT SPAN DIV 1 MHZ pushbut tons The spectrum analyzer automatically picks resolution bandwidth and time division to fit the new span division unless Auto Resolution and Time Auto are cancelled For most purposes leave the TIME DIV control set to AUTO so that Time Auto is in effect in either local or remote control and leave Auto Resolution selected 3 Press the SHIFT REF LEVEL 2 0 dBM push buttons to set the signal to the reference level The spectrum analyzer automatically selects the appropriate input attenuation and IF gain for a reference level at the power level of the CAL OUT signal s funda mental frequency The spectrum analyzer takes into account the MIN RF ATTEN dB and MIN NOISE settings when positioning the attenuation and gain 3 1 Getting Started 494AP Programmers The spectrum analyzer powers up with the automatic modes active and in MAX SPAN to display a complete frequency band You can restore this condition at any time with the lt blue SHIFT gt RESET pushbutton sequence 4041 Controller How do steps 1 2 and 3 in the last example work on a Tektronix 4041 controller The spectrum analyzer commands are inserted in the follow ing GPIB output statement PRINT Throughout
157. ge one of the fol lowing will be returned e 200 0 if under range 200 0 if over range 999 9 if markers are off Examples MAMPL MAM SEC Interaction The amplitude is returned in the current reference level units if in a log display mode or in volts if in a linear display mode If the frequency of the Secondary marker is off screen MLOCAT SECOND and MLOCAT DELTA use the last known Secondary marker amplitude Response to MAMPL query 5 6 NR2 is returned in the Log Mode and NR3 is returned in the Lin Mode MAMPL is not included in the response to SET Interaction If HDR is OFF PRIMAR SECOND or DELTA and the delimiter are eliminated along with the MAMPL header There is no MAMPL command MCEN marker to center command The Primary marker frequency is tuned to the center of the screen Marker execution error message 121 is issued if the marker is not on an active trace Macro Memory Used 1 byte Interaction If MARKER is OFF MCEN sets MARKER to SINGLE In this case since the Primary marker appears at the center of the screen the center frequency does not change When counting at the marker it is the counted frequency that is tuned to center MCEN is not available in ZEROSP or MXSPN There is no MCEN query MCPOIN marker coupled to the display pointer command ON The display pointer tracks the Primary marker OFF The display pointer does not
158. gnal find commands could not find signal MLFTNX MRGTNX MFBIG HRAMPL LRAMPL PKFIND MVRTDB MVLFDB Function either not available or cannot be changed when in multiband sweep Frequency out of range because instrument is in multiband sweep Multiband sweep cannot be started in external or manual sweep Multiband sweep started Multiband sweep stopped Start frequency changed to 1 7 GHz because of using internal mixer Command not available when entering a macro Command not available when NOT entering a macro Command only available when a macro is stopped Memory full macro entry refused Number is already used No macro is stored at NUM No more MDATA commands to read Too many GOSUBs with no RETURN RETURN command not expected Line number used more than once DSLINE command Missing LABEL Missing ENDI Missing NEXT ELSE command not expected ENDI command not expected NEXT command not expected Index out of range DISBUF INDEX VAR INDEX or STNUM INDEX FOR index is already used Missing DONE or RETURN or GOTO aif this error message is issued the macro in progress will be aborted HELP GRAT CLIP M1AsGN M2ASGN MENu MCSroP STSTOP STEP PKFiND TRIG SGTRAK SIGswP TIME Appendix B 494AP Programmers FRONT PANEL RELATIONSHIPS TO MNEMONICS CNTcF COUNT DELFR CREs MCEN FREo IDENT MEXcHG fosan iez
159. gnment DEGAUS and select the EXT MIXER input EXMXR Instruments with Option 07 installed change between the 50 0 and 75 0 inputs IMPED CNTcF FREQ DELFR TMOve CREs TUNE MSTep PROGRAMMABLE SPECTRUM ANALYZER CENTER FREQUENCY ANIDI 92 gt D MARKER FREQUENCY j oe p J BAND i X ster e ES y g FX 1 25 COUNT 8 Do V CENTER MARKER s Ro LJ vw A EM one NARROW vew S SPAN s e 5 CALL SAVE BRAVE 7 ane oO 9 30 0 SPAN i 20 e FREQUENCY gt RESOLUTION SPANIDIV BANDWIDTH R REF VIDEO RESOLUTION RANGE OSC FILTER BANDWIDTH TIME DIV OPTION 07 ONLY Figure 4 1 Front panel Frequency commands 4 3 Instrument Control 494AP Programmers FREQ center frequency command uu ni NUM The instrument centers its span about the value in the command argument The range of values and resolution of the instrument response are the same as for front panel operation Macro Memory Used 6 bytes Examples FREQ 200MHZ FREQ 100000 FRE 200 MHZ Range 0 Hz to 325 GHz Power up value 0 MHz FREQ center frequency query Response to FREQ query l TUNE incremental frequency change command 5 gt NUM NUM The instrument changes its cente
160. goes high the RFD message Ready For Data tells the talker it may place the next data byte on the data bus NDAC Not Data Accepted Each assigned listener holds the NDAC signal line asserted until the listener accepts the data byte currently on the bus When all assigned listeners have accepted the current data byte the NDAC signal line becomes unasserted high telling the talker to remove the data byte from the bus The DAC message Data Accepted tells the talker that all assigned listeners have accepted the current data byte NOTE One handshake cycle transfers one data byte then the listeners reset the NRFD line high and the NDAC line low before the talker asserts DAV for the next data byte transfer Both NRFD and NDAC high at the same time is an invalid state on the bus Management Bus The management bus is a group of five signal lines that are used to control the operation of the IEEE Std 488 GPIB Digital Interface IFC Interface Clear The system controller is the only instrument on the bus allowed to assert IFC IFC is asserted for greater than 100 us to place all instruments in a predetermined state While IFC is being sent only the DCL Device Clear LLO Local Lockout PPU Paral lel Poll Unconfigure and REN Remote Enable interface messages universal commands will be recognized ATN Attention The controller in charge is the only instrument on the bus allowed to assert ATN ATN is asserted when an
161. gram combines both character and number arguments in a link argu ment The link is the colon which delimits the first and second arguments For example the VRTDSP vertical display command employs link arguments to make scale factors available String Argument A string argument is used when a message is to be displayed on a plotter or display unit for human interpre tation as with the RDOUT command The characters are enclosed in quotes to delimit them as a string argument End Block End block binary is a sequence of binary numbers that is preceded by the ASCII code for at EOI must be asserted concurrently with the last data byte The end block can only be the last data type in a message 8 BIT BINARY NUMBER D 2 4 Binary Block Binary block is a sequence of binary numbers that is preceded by the ASCII code for percent and a two byte binary integer representing the number of binary numbers plus one the extra byte is the checksum and followed by the checksum The checksum is the 2 s complement of the modulo 256 sum of all preceding bytes except the Thus the modulo 256 sum of all bytes except the should equal zero to provide an error check of the binary block transfer BINARY BINARY COUNT COUNT HIGH LOW BYTE BYTE CHECKSUM BINARY NUMBER Query Format A query message unit requests either function or display data from the instrument The query message unit f
162. gument gives the resolution as a power of 10 in Hz to which the number is displayed A number to be printed with FFORMAT cannot have a fractional lest than 1 Hz part DECIMAL prints a number in NR2 format The second link argument gives the number of digits to the right of the decimal point The following examples assume that the number indi cated by the result shown is in the X register Examples PRINT 1 5 XREG SCI 14 3 122E 10 PRINT 1 5 XREG SCI 14 WATTS 3 122E 3 WATTS PRINT 1 5 XREG ENG 14 31 12 9 PRINT 1 5 XREG ENG 14 WATTS 71 22E E WATTS PRINT 1 5 VAR 3 DEC 14 2 101 34 PRINT 1 5 VAR 3 DEC 14 0 73652 PRINT 1 5 VAR 3 DEC 14 0 HZ 73652 HZ PRINT 1 5 YREG FORMAT 14 E 2 738 274 PRINT 1 5 YREG FORMAT 14 HZ 2 738 27AHZ PRINT 1 5 14 3 12 738MHZ PRINT 1 5 XREG FFORMT 14 0 12 738 749MHZ PRINT 1 5 XREG FFORMT 14 6 12MHZ PRINT 1 5 XREG 14 2 12 738 3MHZ Macro Memory Used 47 bytes Range The first argument line number is 1 to 16 the second argument starting position is 1 to 40 If FORMAT or FFORMT is used the range of the third argument is 549 755 813 887 maximum value for a 5 byte hexadecimal number If no number is to be printed just a string the string plus the starting position may be up to 40 characters If the string extends beyond the 40 character maximum it will be truncated If a number is
163. he GPIB as either active true or passive true signals Passive true signals occur at a high voltage level and must be carried on a signal line using open collector devices Active true sig nals occur at a low voltage level FUNCTIONAL ELEMENTS The functional elements of the GPIB cover three areas 1 The ten major interface functions of the GPIB are listed in Table A 1 Each interface function is a system element that provides the basic operational facility through which an instrument can receive process and send messages over the GPIB 2 The second functional element is the specific pro tocol by which the interface functions send and receive their limited set of messages 1 IEEE STD 488 GPIB System Concepts 494AP Programmers 3 The logical and timing relationships between allow able states for all interface functions is the third area covered Table A 1 MAJOR GPIB INTERFACE FUNCTIONS Interface Function Symbol Source Handshake SH Acceptor Handshake AH Talker or Extended Talker T or TE Listener or Extended Listener L or LE Service Request SR Remote Local RL Parailel Poll PP Device Clear DC Device Trigger DT Controller C NOTE The IEEE Std 488 standard defines the ten interface functions the specific protocol and timing relationships by the use of state diagrams Not every instrument on the bus will have all ten interface functions incor porated because only those functions impor tant to a partic
164. he spectrum analyzer is executing any device dependent message other then WAIT the response is handled the same as described for the 495P 495P Option 05 494AP and 492AP GET Group Execute Trigger 494P 492AP 495P 495P Option 05 494AP GET requires firmware action so handshake occurs only when the interrupt can be handled The effect of GET is masked by DT Device Trigger 492P 496P Handshake occurs only when the microcomputer is not executing a device dependent mes sage unit other than WAIT GET is not masked Reference Level 494P 492AP 495P 495P Option 05 494AP The minimum reference level is 117 dBm The delta amplitude range is 57 75 dB and slides depending on the reference level when the delta amplitude mode is entered 492P 496P The minimum reference level is 123 dBm The deita amplitude range is 63 75 dB and slides depending on the reference level when the delta amplitude mode is entered RDOUT Command 494P 492AP 495P 495P Option 05 494AP The remote to local transition will always return RDOUT to NORMAL i e any messages sent to the crt with RDOUT commands will be replaced by the regular crt readout 492P 496P If the remote to local transition occurs after UNT or UNL messages sent to the crt via RDOUT may be retained on the screen The regular crt readout will be returned by changing any control whose current condition is reported on the crt Compatibility Only
165. he start of the search the LFTNXT MLFTNX HRAMPL and LRAMPL commands can also be used to find all signals in a given waveform Because the oscillators are counted on an active trace the marker related commands are slower on an active trace than on a stored trace Speed will be increased at the expense of some accuracy by turning BVIEW OFF and commanding SAVEA ON after the single sweep and before the search is started SAVEA OFF should be sent before the next sweep A signal search program using RGTNXT is given in connection with the description of the REPEAT com mand Measuring Signal Frequency with COUNT To measure the frequency of a signal center the sig nal on screen or move the marker to the signal This can be done by using a FMAX CENSIG combination or PKFIND The signal level at center screen point 500 or at the marker must be at least 20 dB above the noise level A 10 MHz div span div will provide a good compromise between the time required to span down and the need to be 20 dB above the noise Send COUNT COUNT and input the signal frequency The number returned will have a least significant digit of the current count resolution CRES command 100 Print z SIG WAI FMA CEN 110 Print z SIG WAI FMA POI FMIN POI 120 Input z X Y X1 Y1 10 9 Helps and Hints 494AP Programmers 130 If Y Y1 lt 50 then 200 140 Print z COUNT COUNT 150 Input 2 f 200 CODE TO HANDLE LOW SIGNAL LEVEL CONDITIO
166. horter or send the frequency in scientific notation but this example shows the conversational format of spec trum analyzer messages that makes them readable therefore human oriented The spectrum analyzer device dependent messages in this manual are downward compatible with the Tek tronix 49XP Series 492AP 495P 495P Option 05 and 275XP Series programmable spectrum analyzers except as noted later in this section under Spectrum Analyzer Compatibility SYNTAX DIAGRAMS Spectrum analyzer messages are presented in this manual in syntax diagrams that show the sequence of elements transferred over the bus Each element is enclosed in a circle oval or box Circles or ovals contain the mnemonics for literal ele ments i e a character or string of characters that must be sent exactly as shown Because most mnemonics may be shortened the required characters in command and query literal elements i e the first three characters of the element are shown larger than optional charac ters Although mnemonics are shown all upper case the spectrum analyzer accepts either upper case or lower case ASCII characters Query response characters are shown exactly as they will be returned Boxes are used for defined elements and contain a name that stands for the element defined elsewhere NUM is such an name and is defined under Numbers later in this section Elements of the syntax diagram are connected by arrows that show the possible pat
167. hs through the diagram 1 the sequence in which elements must be transferred Parallel paths mean that one and only one of the paths must be followed while a path around an element or group of elements indicates an optional skip Arrows indicate the direction that must be followed usu ally the flow is to the right but if an element may be repeated an arrow returns from the right to the left of the element Some examples of such sequences follow gt OY SPECTRUM ANALYZER INPUT MESSAGES Input Message Format A remote control message to the spectrum analyzer comprises one or more message units of two types The message units either consist of commands that the spec trum analyzer inputs as control or measurement data or they consist of queries that request the spectrum analyzer to output data One or more message units can be transmitted as a message to the spectrum analyzer Message units con tain ASCII characters binary may also be used for data The spectrum analyzer accepts either upper case or lower case characters for the mnemonics shown in the syntax diagrams 2 1 Device Dependent Message Structure and Execution 494AP Programmers i FORMAT i CHARACTER Message Unit Delimiter Message units are separated by a semicolon A semicolon is optional following the last message unit Message Terminator TERM The end of message terminator may be either the END message EOI asse
168. ical Parts list in the Service Manual Volume 2 Standards and Conventions Used Most terminology is consistent with standards adapted by IEEE and IEC A glossary of terms is pro vided in Appendix A Abbreviations in the documentation are consistent with ANSI Y1 1 1972 GPIB functions con form to the IEEE 488 1978 Standard and the Tektronix Interface Standard for GPIB Codes Formats Conven tions and Features Copies of ANSI and IEEE standards can be ordered from the Institute of Electrical and Elec tronic Engineers Inc Contact your local Tektronix Field Office or representative if you have questions regarding the Tektronix reference document Change History Information Any change information that involves manual correc tions or additional information is located behind the tabbed Change Information page at the back of this manual History information as well as the updated data is combined within this manual when the page s is revised A revised page is identified by a revision date located in the lower inside corner of the page Unpacking and Initial Inspection Instructions for unpacking and preparing the instru ment for use are described in Section 3 of the Operators Manual Storage and Repackaging Instructions for short and long term storage and instrument repackaging for shipment are described in Section 3 of the Operators Manual 494AP Programmers TABLE OF CONTENTS Page T
169. ications in the IEEE 488 standard refer to Appendix A in this manual for the basic con cepts of the IEEE 488 standard Table 1 2 lists interface capabilities as defined in the standard Table 1 2 PROGRAMABLE SPECTRUM ANALYZER IEEE 488 INTERFACE FUNCTIONS Function Implemented As Source Handshake SH1 Acceptor Handshake AH1 Talker T5 Listener L3 Service Request SR1 Remote Local RL1 Parallel Poll PP1 Device Clear DC1 Device Trigger DT1 Controller CO Source Handshake SH1 The spectrum analyzer has complete capability to transfer messages to other devices on the bus Although tri state drivers are used on the data lines T1 DAV delay for data setting is greater than 2 us Acceptor Handshake AH1 The spectrum analyzer has complete capability to receive messages on the bus Talker T5 The spectrum analyzer has the complete talker func tion including serial poll it unaddresses as a talker when addressed as a listener The instrument operates in a simple system in a talk only mode if the TALK ONLY switch is set to 1 up Listener L3 The spectrum analyzer has the complete listener function unaddresses as a listener when addressed as a talker The instrument operates in a simple system in a listen only mode if the LISTEN ONLY switch is set to 1 up Service Request SR1 The spectrum analyzer has the complete service request function asserts SRQ service request for the conditions indicated under STATUS B
170. ich requires two numbers and uses both the X and Y registers the START FREQ goes into YREG and the STOP FREQ goes into XREG For a description of the command argu ments see the description of the command whose mnemonic is the same as the argument Examples See Example Descriptions Below PUTREG STEP See 1 PUTREG RESBW f See 2 PUTREG STSTOP See3 PUTREG MVRTDB See 4 Example Descriptions 1 Puts the value of XREG into the step size 2 Sets the resolution bandwidth to the value in XREG 3 Puts the contents of YREG into START FREQ and the contents of XREG into STOP FREQ 4 Puts the value of XREG into X and calls the move right X dB routine Macro Memory Used 2 bytes There is no PUTREG query EXCHG exchange X and Y registers command The EXCHG command exchanges the current con tents in XREG and YREG The following example illustrates the use of the EXCHG command 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Print z ENTER 5 110 Print z ENTER 10 120 Print z EXCHG 130 Print z STNUM 1 140 Print z VAR 1 150 Input z r 160 Printr Line 100 Enters 5 into XREG Line 110 Moves the contents of to YREG and enters 10 in XREG Line 120 Enters 5 into XREG and moves 10 into YREG Line 130 Stores the contents of XREG in variable number 1 Line 150 Puts the contents of variable number 1 into r Macros 494AP Programmers Line 160 Prints the contents
171. imitations are This portion of the manual will try to help you gain that understanding and to use the power of the spectrum analyzer in your applica tion with more accurate and predictable results Understanding How Waveform Processing Works There are two sets of signal processing commands commands that move the marker and commands that move the display data point See Sections 5 and 8 of this manual for more information Each set of commands uses a different signal finding algorithm Commands that move the display data point use the same algorithm as the commands used in previous 490 series spectrum analyzers This algorithm looks for the signal shape pro 10 8 duced by a continuous wave cw signal passing through the resolution filters of the spectrum analyzer Complex spectra such as those produced by amplitude fre quency or pulse modulation or by signals with significant amounts of drift or phase noise may be missed In contrast the marker related signal processing commands allow through the STYPE command a choice of signal processing algorithms These commands iden tify a candidate signal by means of three points a peak and a point 3 dB down on each side of the peak Whether or not the candidate is recognized as a signal depends upon the processing mode chosen When SPURS is chosen all candidates are taken to be signals When CW is chosen a signal to be a signal must be at least half as wide as would be predicte
172. in a controller program to get the current value of the given argument setting or variable The value is placed in the X register For a description of the com mand arguments see the description of the command whose mnemonic is the same as the argument When ENTER does not have an argument the contents of XREG are copied into YREG both XREG and YREG will hold the same value Sample Entries ENTER POINT The X POINT value will be put into XREG and the Y POINT value will be put into YREG ENTER STSTOP The start frequency will be put into YREG and the stop frequency will be put into XREG VAR The variable is entered into XREG e g VAR NUM VAR XREG VAR YREG VAR VAR NUM If the index is out of range macro execution error mes sage 176 is issued and the macro is aborted DISBUF The display buffer point indexed by NUM XREG YREG or VAR NUM is entered into XREG e g DISBUF NUM DISBUF XREG DISBUF YREG DISBUF VAR INDEX Execution error message 176 is issued either if the overall index for DISBUF the part fol lowing the first colon is outside the range of 1 1000 or if the NUM indicating which variable to use is outside of the range of 1 30 NOTE The GETWFM command must be used before ENTER DISBUF can be used See the GETWFM command description for more information NUM A number with or without a units designator is entered into XREG Examples ENTER MFREQ ENTER MAMPL SEC ENTER
173. ind and mark an adequate tape file These statements do the job 100 Open 2 WAVEFORM OPEN REP CLIP YES 110 Print 2 120 Close 2 These statements return the data from the tape 100 Open 2 WAVEFORM 110 Input 2 120 Close 2 Storing Settings If a particular series of settings are commonly used in an application it is recommended that these settings be stored within the spectrum analyzer using the STORE command This practice will save program storage in the controller programming time and bus transfer time The settings can be recalled whenever needed with the RECALL command you need to store more settings than can be held in the spectrum analyzer at one time the settings data can be conveniently exchanged between the controller and the analyzer with the RDATA command and query 10 6 Using PLOT The spectrum analyzer can generate a plot of the display directly on a e Tektronix 4662 Option 01 e Tektronix 4662 Option 31 e Tektronix 4663 in the 4662 emulation mode e Hewlett Packard HP7470A Hewlett Packard HP7475A Hewlett Packard HP7580B e Hewlett Packard HP7585B e Hewlett Packard HP7586B e Gould 6310 e Gould 6320 All selected waveform graticule marker and crt readout data can be plotted PLOT sent to the spec trum analyzer causes it to output the plotter code when addressed as a talker Address the plotter as a listener then monitor the EOI line to allow the controller to cause
174. inding example Marker System 494AP Programmers LEVEL FREQUENCY SPAN DIV rer 20DBM CEN 0006H7 MKR 28 8DBM 800 0006H7 e 1 8 REO REF VIDEO RESOLUTION DISPLAY RANGE OSC FILTER BANDWIDTH Figure 5 6 Signal finding example LEVEL FREQUENCY rer 50DBM CEN S69KHZ MKR MKR 201 9KHZ L Fay REF VIDEO RESOLUTION RANGE OSC FILTER BANDWIDTH Figure 5 7 Signal finding example 5 18 SGERR signal find error command ON The spectrum analyzer asserts SRQ if RQS is ON when any of the following conditions exist e The internal signal identification routine cannot find the signal requested by the MFBIG MRGTNX MLFTNX HRAMPL or LRAMPL commands e The internal signal identification routine cannot find the amplitude requested by the PKFIND PKCEN MVRTDB or MVLFDB commands e The requested bandwidth cannot be found by the BWMODE command OFF The spectrum analyzer does not assert SRQ when any of the above commands fail Power up value OFF Macro Memory Used 2 bytes Interaction RQS must be on for marker execution warning message 130 to be issued SGERR signal find error query Response to SGERR query MISCELLANEOUS ZOOM command The ZOOM command moves the Primary marker fre quency to the center frequency and sets the SPAN fre quency span division to the next smaller span division if possib
175. instrument connected to the bus is being enabled as a talker or listener or when sending other interface control messages As long as the line is asserted low only instrument address codes and interface control messages are sent over the bus When the ATN line is unasserted only those instruments enabled as a talker and listener can send and receive data over the bus Ke o IEEE STD 488 GPIB System Concepts 494AP Programmers PRIMARY SECONDARY LISTEN ADDRESS ADDRESS 2 lt 66 108 S L IU ATN ASSERTED CONTROLLER EOI ATN ASSERTED ASSERTED INSTRUMENTS Figure A 4 An example of data byte traffic on the GPIB ATN CONTROLLER DAV TALKER NRFD LISTENER NDAC LISTENER LAST INTERFACE MSG BYTE FROM CONTROLLER FIRST DATA BYTE FROM TALKER DEVICE DEPENDENT MSG Figure A 5 A typical handshake timing sequence idealized Byte capture time is dependent on the slowest Instrument involved in the handshake RFD means Ready For DATA DAC means Data Accepted A 7 IEEE STD 488 GPIB System Concepts 494AP Programmers SRQ Service Request Any instrument connected to the bus can request the controller s attention by assert ing the SRQ line The controller responds by asserting ATN and executing a serial poll routine to determine which instrument is requesting service The instrument requesting service responds with a device dependen
176. int SIGNAL ir 170 Print z REFLVL 20 DBM 180 Nexti Line 110 Sets span div and reference level for the Start of the signal search and selects narrow video filter to smooth the data for the routine The single sweep mode is selected so new data can be acquired on com mand Line 120 Starts the loop Line 130 Tunes to a harmonic of the calibrator signal then starts a sweep to acquire new data The WAIT guarantees digital storage is filled with updated data before proceeding Line 140 FIBIG finds the calibrator harmonic it should be the only signal on screen TOPSIG automati cally changes analyzer gain or input attenuation to bring the signal peak to the reference level top of screen These and other waveform processing commands allow you to analyze signals without reading in all the display data and operating on it in your controller Line 150 Inputs the analyzer response Line 160 Because the response to each query in line 140 begins with a mnemonic for the function the analyzer output string acquired in line 150 is intelligible as is and the frequency and reference level readings are printed at the controller Line 170 Readies the spectrum analyzer to do it again Line 180 Goes around again The waveform processing commands and query allow you to analyze data without reading waveforms and manipulating them in your controller More details can be found in Sections 5 and 8 of this
177. inted manuals Hence your manual may contain new change information on following pages A single change may affect several sections Since the change information sheets are carried in the manual until all changes are permanently entered some duplication may occur If no such change pages appear following this page your manual is correct as printed
178. ith a sweep that falls within one band e Entering a sweep that falls within one band using the STSTOP command e Entering FRORNG e Changing the span with the SPAN ZEROSP or MXSPN commands With MARKER ON the center frequency is set to the Primary marker frequency With MARKER OFF the center frequency remains at the center frequency of the multiband sweep The span is set to the span of the mul tiband sweep or is defaulted to MXSPN if the multiband sweep value is larger than the maximum span of the band containing the center frequency The command change that caused the exit from multiband sweep will then change either the center frequency or span or both COMPARING THE STATUS BYTE AND THE ERR RESPONSE The spectrum analyzer status byte and ERR response described in Section 9 play complementary roles in GPIB system programming The status byte is the spectrum analyzer response to a serial poll The ERR response is the spectrum analyzer answer to a device dependent query message The status byte pro vides information about instrument conditions category normal abnormal busy command error exe cution error etc The ERR response details the cause of abnormal status i e what kind of error or warning prompted the spectrum analyzer to assert SRQ and report abnormal status Status bytes are not stacked The code for the condi tion that caused the SRQ is not updated although bit 5 reflects the present instrument st
179. ived The instrument remains busy until it is done executing the commands in the buffer unless the process is stopped by the DCL Device Clear or SDC Selected Device Clear interface messages While busy further input is not accepted see STATUS BYTE in Section 9 in this manual for more on busy status Output if requested is begun only after the entire input message is executed Because display measurement data input and out put and waveform processing share the same buffer conflicts can arise This is discussed in the Interaction part of the CURVE command in Section 7 under Display Data Point Commands Interaction in Section 8 and is further expanded on under Multiple Use of Display Buffer For Waveform Processing and I O in Section 10 all in this manual Command Format A command message unit either sets an operating mode or parameter or it transfers data to the instrument The command format to set a mode or parameter includes the following possible paths FORMAT amp CHARACTER p E CHARACTER Because the general command format for display data transfers is complicated it is omitted see the data I O commands in Section 7 of this manual for the specific command syntax Header Header elements are mnemonics that represent a function for example FREQ for center frequency and CURVE for the display trace Device Dependent Message Structure and Execution 494AP Programmers Header Delimiter S
180. ivide Y by X register command The DIVIDE command divides the contents of YREG by the contents of XREG and puts the result in XREG e g XREG YREG The following example illustrates the use of the DIVIDE command 10 25 90 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Print z ENTER 10 110 Print z ENTER 5 120 Print z DIVIDE 130 Print z STNUM 1 140 Print z VAR 1 150 Input z r 160 Printr Line 100 Enters 10 into XREG Line 110 Moves the contents of XREG to YREG then enters 5 in XREG Line 120 Divides the contents of YREG 10 by the contents of XREG 5 YREG still contains 10 Line 130 Stores the contents of XREG in variable number 1 Line 150 Puts the contents of variable number 1 into r Line 160 Prints the contents of r 2 Macro Memory Used 1 byte Range 9 999 999 999 999 E 99 to 9 999 999 999 999 E 99 Interaction The YREG is unchanged after the DIVIDE command There is no DIVIDE query REGISTER COMMANDS The register commands put the number in X register into a setting PUTREG exchange the contents of X register and Y register EXCHG convert the number in X register to an integer INTEGR put the contents of Y register into X register POP and enter a value into the X register ENTER PUTREG put X register into a setting command The PUTREG command sets the argument to the value currently in XREG except STSTOP wh
181. k however the spectrum analyzer does not begin talking until it finishes executing the message in line 120 This assures that the spectrum analyzer updates the FRQRNG query response before handshaking out array element f i 1 in line 130 Synchronizing with the Sweep Spectrum data can be acquired synchronously with the sweep that updates digital storage if a WAIT com mand is inserted in the message to the spectrum analyzer Generally WAIT is placed immediately after a SIGSWP command that arms a sweep so that data is acquired from a full sweep WAIT delays the execution of commands or queries that follow in the same message until the full sweep is completed This means you can direct the spectrum analyzer to acquire process and output data all in the same message If the commands or queries you add to process or output data follow WAIT the results will be based on data acquired by the SIGSWP command For example enter 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Dim p 5 2 110 Print z SIGSWP 120 Fori 1to5 130 Print z FREQ 5 GHZ SIGSWP WAIT FMAX POINT 140 Input z p i 1 p i 2 150 Nexti Line 110 Sets the spectrum analyzer to the single sweep mode if the spectrum analyzer is not already in the single sweep mode Succeeding SIGSWP commands arm the sweep Line 130 Illustrates how to use WAIT WAIT fol lows SIGSWP and precedes the command and query that ready the spectrum analyzer to output the updated data
182. ker does not move Marker System 494AP Programmers Macro Memory Used 1 byte Interaction If MARKER is OFF MFBIG sets MARKER to SINGLE If SGERR is ON marker execution warning message 130 is issued if a signal is not found The definition of the criteria for a signal is set by the THRHLD and STYPE commands MFBIG marker peak find query Response to MFBIG query FOUND is returned if the last MFBIG command found a signal FAILED is returned if the last MFBIG command did not find a signal If the MFBIG query is given before any MFBIG command FAILED is returned MLFTNX marker left next command The MLFTNX command moves the Primary marker to the peak of the next signal to the left of the present marker position If no signal peak is found the marker does not move Macro Memory Used 1 byte Interaction If MARKER is OFF MLFTNX sets MARKER to SINGLE If SGERR is ON marker execution warning message 130 is issued if a signal is not found The definition of the criteria for a signal is set by the THRHLD and STYPE commands MLFTNX marker left next query Q Response to MLFTNX query os FOUND is returned if the last MLFTNX command found a signal FAILED is returned if the last MLFTNX command did not find a signal If the MLFTNX query is given before any MLFTNX command FAILED is returned 5 11 Marker System 494AP Programmers PKFIND marker to maximum above threshold command The
183. l C Unlisten LLE Remote Messages Sent Attention Data Accepted Data Valid Device Clear Group Execute Trigger a Multi line messages A 4 Table A 2 Continued INTERFACE MESSAGES REFERRED TO IN THIS APPENDIX AND FUNCTIONS Interface Mnemonic Message Function Remote Messages Sent Continued Go To Local via C IFC Interface Clear C LLO8 Local Lockout via C My Secondary Address via C My Talk Address via C PPC Parallel Poll Configure via C PPDa Parallel Poll Disable via C PPE Parallel Poll Enable via C PPU Parallel Poll Unconfigure via C REN Remote Enable C RFD Ready For Data AH SDC Selected Device Clear via C SPD Serial Poll Disable via C SPE Serial Poll Enable via C SRQ Service Request SR TCT Take Control via C Unlisten via C Untalk via C Multi line messages DEVICE DEPENDENT MESSAGES The IEEE standard does not specify the coding of device dependent messages messages that control the internal operating functions of a device After addressing a talker and the required number of listeners via interface control messages the controller unasserts the ATN line false on the bus When ATN becomes false high any commonly understood 8 bit binary code may be used to represent a device dependent message However the standard recommends that the alphanumeric codes associated with the numbers sym bols and upper case
184. lay data point to the point in digital storage with the largest Y value If the largest Y value is located at more than one point the first left most point is acquired The optional arguments are two display X values The FMAX command will limit its search over this X range otherwise the full X range 1 to 1000 will be searched Macro Memory Used 5 bytes Interaction See Display Data Point Commands Interaction There is no FMAX query FMIN find minimum value command Ape This routine sets the display data point to the point in digital storage with the smallest Y value If the smallest Y value is located at more than one point the first left most point is acquired The optional arguments are two display X values The FMIN command will limit its search over this X range otherwise the full X range 1 to 1000 will be searched Macro Memory Used 5 bytes Interaction See Display Data Point Commands Interaction There is no FMIN query Data Point Commands Interaction 1 The waveform processing commands in this sec tion operate only on the waveform specified by the last WFMPRE or CURVE command either A or B or full both A and B The waveform involved is first copied into a buffer If the waveform is only half resolution either A or B it is duplicated in the buffer to make a full 1000 point waveform before processing Thus whether the com mand operates on A or B or both
185. lay pointer Macro Memory Used 1 byte Interaction If MARKER is OFF MKDP sets MARKER to SINGLE There is no MKDP query MLOCAT marker location query MLOCAT or MLOCAT PRIMAR The amplitude and frequency are returned for the Primary marker MLOCAT SECOND The amplitude and frequency are returned for the Secondary marker MLOCAT DELTA The amplitude and frequency are returned for the Primary marker with respect to the Secondary marker Interaction In LOG the amplitude is returned in reference level units In LIN the amplitude is returned in volts If the frequency of the Secondary marker is off screen MLOCAT SECOND and MLOCAT DELTA use the last known Secondary marker amplitude NOTE If the amplitude of the marker being requested is out of the range of digital storage one of the following will be returned e 200 if under range 200 if over range 999 9 if markers are off If the requested marker is off 9 999999E 99 will be returned for frequency Response to MLOCAT query PRIMAR NR2 is returned in the Log Mode and NR3 is returned in the Lin Mode The marker frequency is returned first followed by the marker amplitude If the frequency of the Secondary marker is off screen MLOCAT SECOND and MLOCAT DELTA use the last known Secondary marker amplitude Interaction If HDR is OFF PRIMAR SECOND or DELTA and the following delimiter are eliminated along
186. le in the front panel 1 2 5 sequence If the Marker System 494AP Programmers optional number argument is given the span division is reduced NUM times Numbers less than 1 are rounded to 1 Execution warning message 111 is issued if the spec trum analyzer defaults to the lowest span division because the span could not be reduced the requested number of times Macro Memory Used 2 bytes Interaction Marker execution error message 121 is issued if the Primary marker is not on an active trace If MARKER is OFF ZOOM sets MARKER to SINGLE In this case since the marker initially appears at the center screen the effect is to decrement the span only There is no ZOOM query ZETIME zero span command ON In zero span the marker readout is amplitude and time OFF In zero span the marker readout is amplitude and frequency Macro Memory Used 2 bytes Power up value OFF Interaction The ZETIME command has no effect when the instrument is in a non zero span If the markers are on different traces the Secondary marker will move to the Primary marker trace under either of the following conditions Under the same conditions if the Secondary marker is off screen it will move on screen e f the ZETIME ON command is given with the Pri mary marker on zero span trace e f the Primary marker is moved to a zero span trace while ZETIME is ON ZETIME zero span query Erm 0 Resp
187. le the Auto Resolution mode selected a resolution bandwidth to go with a span of 1 MHz What is that bandwidth The query RESBW readies the spec trum analyzer to output the answer The query can be included in any message to the spectrum analyzer It is executed in its turn This means that if RESBW precedes the SPAN command in the pre vious example the spectrum analyzer informs you of the old rather than the new resolution bandwidth More than one query can be contained in a message to ask for both resolution bandwidth and for instance whether a video filter is on Just add these queries into the message used in the previous example and combine the message with the controller GPIB input statement 110 Print z FREQ 100 MHZ SPAN 1 MHZ REFLVL 20 DBM RESBW VIDFLT 112 Input z p 114 Print p If a query that has a lengthy response e g CURVE SET WFMPRE is included as part of this program character string p must be dimensioned large enough to accommodate the message Whatever the controller input statement the actions shown in the syntax diagram below must be taken to receive a message from the spectrum analyzer SPECTRUM ANALYZER QUERY RESPONSE OUTPUT The PRINT and INPUT statements above describe the two steps necessary to get output from the spectrum analyzer The PRINT statement includes the query sent to the spectrum analyzer The INPUT statement receives the query response In 4041 BASIC both ste
188. llel poll the GPIB system must first be configured In a typical sequence the controller first sends an UNL command to clear the bus of listeners then the listen address of the device to be configured Following this the controller sends the PPC Parallel Poll Configure command fol lowed by a PPE Parallel Poll Enable message The PPE message contains coded information that tells the selected instrument which data line will carry the PP IEEE STD 488 GPIB System Concepts 494AP Programmers status bit for that device This entire sequence is repeated for each instrument to be configured The PPE message s sent by the controller has the form X110SPPP Bit 4 S is called the sense bit and the three least significant bits PPP represent an octal number 0 through 7 that corresponds to a specific line on the data bus that an instrument must assert if its internal status has the same value as the sense bit S may equal 1 or 0 The actual parallel poll takes place after each instru ment has been completely configured The concept is to have the controller receive one data byte that contains status information on all of the addressed instruments To receive this status byte the controller asserts the EOI line and the ATN line The assertion of EOI may be coin cident with ATN or later so long as both are asserted This may occur any time after the last PPE message The controller then reads the data bus lines while ATN and EOI ar
189. llowing descrip tion After a signal is found it is often moved to center screen and to the reference level with either the CENSIG or TOPSIG commands for the display point related func tions The accuracy of the vertical display and the refer ence level determine how closely the point of interest can be moved to the reference level For CENSIG the span division determines how closely the point of interest can be moved to center screen On an active trace the oscillator frequencies are counted at the marker and the values are used to set the center fre quency for the MCEN command Thus MCEN will gen erally be more accurate than CENSIG These commands may be applied repetitively for greater accuracy Setting the Threshold Both sets of signal finding commands use a thres hold that may be set above the noise and below the sig nal level so that small noise peaks will not be falsely identified as signals The threshold for the display point commands is sent in screen units as an optional argu ment to the commands The threshold for the marker commands is set in dBm or dBv dBmv or dByv by the THRHLD command No signal threshold setting will work in every case An estimate of the noise level may be made by finding the amplitude of the negative noise peaks with FMIN or MMIN and adding a constant to get an estimate of the positive noise peaks Because the peak to peak noise variation is a function of resolution bandwidth the con
190. low the standard There is no PLOT command PTYPE plotter type command TK4662 Selects the Tektronix 4662 Opt 01 or the 4663 in a one pen configuration as the plotter driven by the data generated by PLOT TKOP31 Selects the Tektronix 4662 Opt 31 or the 4663 in a two pen configuration as the plotter driven by the data generated by PLOT HP7470 Selects the Hewlett Packard HP7470A as the plotter driven by the data generated by PLOT MCOLOR Selects the Hewlett Packard 7475 7580B 7585B or 7586B or the Gould 6310 or 6320 as the plotter driven by the data generated by PLOT NUM 0 TK4662 1 TKOP31 2 HP7470 3 MCOLOR Macro Memory Used 2 bytes Power up value The last value stored in memory PTYPE plotter type query Q 4 35 Instrument Control 494AP Programmers Response to PTYPE query PTYPE POFSET set K command NUM Sets the reference position for plotting waveforms Although the range is 0 to 255 the range visi ble on the screen is 25 at the bottom to 225 at the top The nearest limit is used if the selected number is out of range no error is reported Range 0 to 255 Macro Memory Used 2 bytes Power up value The last value stored in memory POFSET set K query Response to POFSET query ea ECR end of sweep corrections command This command causes oscillator corrections t
191. ment When markers are turned on MFREQ is set to the center frequency of the marker trace unless the marker is on a recalled trace that had a stored marker frequency Interaction If MARKER is OFF sets MARKER to SINGLE MFREQ causes marker execution error message 120 to be issued if the Primary marker is on an inactive trace and the frequency is not on the screen MFREQ moves the Primary marker to center screen and changes center frequency if the Primary marker is on an active trace and the frequency is not on the screen MFREQ marker frequency query MFREQ or MFREQ PRIMAR The frequency is returned for the Primary marker MFREQ SECOND The frequency is returned for the Secondary marker MFREQ DELTA The frequency is returned for the Primary marker with respect to the Secondary marker Interaction Any MFREQ query returns 9 999999E 99 if the requested marker or delta is not on Response to MFREQ query eme 90 aa Ji Interaction If HDR is OFF PRIMAR SECOND or DELTA and the following delimiter are eliminated along with the MFREQ header 5 7 Marker System 494AP Programmers MKTIME marker time command Ca The MKTIME command sets the time of the Primary marker with respect to the trigger point 1 2 division to the left of the screen to the value given in NUM Macro Memory Used 6 bytes Examples MKTIME 1MS 1 Power up value Marke
192. mmers WAVEFORM PROCESSING The commands in this section allow local processing of spectrum data by the spectrum analyzer Some of these commands operate on a display data point This is an ordered pair an X and a Y value that corresponds to a point on the spectrum analyzer display On command the spectrum analyzer gets a display data point from the current digital storage waveform The point is held in memory until another command updates the data point query requests that the spectrum analyzer report the point Other commands change spectrum analyzer set tings automatically to center it on the point Commands that update the display data point direct the spectrum analyzer to a new point POINT find the largest or nearest signal FIBIG LFTNXT RGTNXT or search for the maximum or minimum value FMAX FMIN A query POINT returns the X and Y values of the display data point This section covers how the waveform processing commands and query work Two programs at the end of Section 2 in this manual show some of these commands in use Waveform processing techniques are offered in Section 10 of this manual Use in Macros Most of the waveform processing commands in this section can be incorporated into macros designed to your specific needs No queries can be used within mac ros Since there is a total of 8k bytes of memory dedi cated for macro use it is important that you know the number of bytes used for each command
193. mples Many combinations of languages and controllers may be used for programming the spectrum analyzer over the GPIB The examples in this manual are given in the BASIC language specifically in the version of BASIC used by the Tektronix 4041 System Controller Other ver sions of BASIC will probably have similar syntax Some controllers may require additional statements to set up data transfer over the GPIB For example 4041 BASIC contains optional OPEN and SET DRIVER state ments that set GPIB communications parameters These statements are not included in the program examples because the default parameter values are suitable for simple programs such as the examples The statements may be helpful in writing programs involving multiple 1 O channels such as tape files or other GPIB controller instruments Refer to the manual of the controller you are using for the statements needed in your application In these examples the spectrum analyzer s primary address is assumed to be 1 See Section 1 of this manual for instructions on how to set the GPIB address switches Section 6 494 Programmers MACROS Some of the lines in the examples extend beyond the column width limitations When this happens the line is broken where a natural space occurs and the remainder of the line is indented on the immediately following line Because of this natural space a space must be added between the two example lines when joining them to form
194. ms in ASCII the WFMPRE command in Section 8 explains how to change modes Here is a program in 4041 BASIC that acquires an ASCII waveform It gets a Full 1000 point waveform with A and B memories merged a power up condition Array wfm in this program must be dimensioned to 5000 100 Dim wfm to 5000 110 Input prompt cur z wfm See Section 10 in this manual for help in plotting the waveform Getting Smarter Signal analysis can be even easier Put the spectrum analyzer to work to find and measure signals with its internal waveform processing capabilities The full set of waveform processing commands is described in Section 8 of this manual and more instructions for their use are found in Sections 5 and 10 of this manual To get started getting smarter here is simple application The following 4041 program catalogs the first 10 har monics of the CAL OUT signal Connect a 100 MHz cali brator before running this program If the instrument is set to other than the power up state precede the pro gram with the INIT command As in the other programs in this manual Z is the variable that holds the value of the spectrum analyzer GPIB address 80 2 1 ADDRESS OF SPECTRUM ANALYZER 90 Print z INIT 100 CATALOG ROUTINE 110 Print z SPAN 1 MHZ REFLVL 20 DBM VIDFLT NARROW SIGSWP 120 Fori 1 to 10 130 Print z FREQ i 1 0E 8 SIGSWP WAIT 140 Print z FIBIG TOPSIG FREQ REFLVL 150 Input 2 160 Pr
195. n died GET is executed immediately stopping the current sweep and rearming the sweep If the spectrum analyzer is busy when GET is received it will wait until the instru ment is no longer busy to execute GET 6 Parallel polls are handled by the spectrum analyzer so PPC PPE PPD and PPU must wait for the spectrum analyzer to service the interrupts before they can be executed This assumes that the spectrum analyzer was addressed for the parallel poll sequence 9 10 Busy and end of sweep are independent Busy exists only while the spectrum analyzer is acting on a com mand and end of sweep indicates that sweep and data updating are complete If a single sweep command is sent the spectrum analyzer remains busy only until it can start the sweep while end of sweep does not occur until the operation is complete When polled the spectrum analyzer reports a status code related to its SRQ if any Bit 5 always indicates the current condition A serial poll clears the status byte that is reported Since status is stacked a new SRQ may be sent immediately DT define triggered events command ON GET is enabled to trigger a new sweep OFF The response to GET is disabled Macro Memory Used 2 bytes Power up value ON Interaction If DT is OFF and GET is received exe cution error message 45 will be issued DT define triggered events query Response to DT query EVENT event information query
196. ncy or delta to which the step size is to be set is larger than 155 GHz the step size will be set to 155 GHz If STEP has not been set MSTEP and PSTEP set STEP to the follow ing values Instrument Control 494AP Programmers e The absolute value of the delta frequency is put into step size if delta markers are on The marker frequency is put into the step size if delta markers are off and the Tune Marker Mode is on Otherwise The center frequency is put into the step size if delta markers are off and the Tune CF Mode is on STEP step size query Response to STEP query MSTEP minus step command This command decreases the center frequency if you are in the tune frequency mode by the value set in the STEP command if possible If you are in the tune marker mode the primary marker frequency is decreased If the step marker is on a saved trace and you go outside the displayed trace execution error message 120 will be issued Macro Memory Used 1 byte Power up value See Interaction that follows Interaction If the frequency or delta to which the step size is to be set is larger than 155 GHz the step size will be set to 155 GHz If STEP has not been set MSTEP will set STEP to the following values e The absolute value of the delta frequency is put into step size if delta markers are on e The marker frequency is put into the step size if delta markers are off and the Tune Marker Mode is on
197. nd RFATT PLSTR VIDFLT PULSE STRETCHER WIDE VIDEO FILTER and NARROW VIDEO FILTER Sweep Control FREE RUN INT LINE and EXT TRIG SINGLE SWEEP TIME DIV VIEW A VIEW B SAVE A SAVEA B SAVE BMINA STORE DISP DSTORE RECALL DRECAL MAX HOLD PEAK AVERAGE READOUT GRAT ILLUM BASELINE CLIP HELP STORE RECALL SETTINGS RECALL Register Data RDATA PLOT PLOT Plotter Type Selection PTYPE Plot B A Reference POFSET End of Sweep Corrections ECR Register Valid RVALID SRQ These commands are related to front panel control functions they are not actually labeled on the front panel b available only on instruments with Option 07 Installed 4 1 Instrument Control 494AP Programmers Table 4 1 cont Name Mnemonic Marker System Control A MKR and MARKER MARKER Marker on Trace MTRACE ASSIGN 1 M1ASGN ASSIGN 2 M2ASGN dB Hz NSELVL SIGNAL TRACK SGTRAK Marker Positionin Display Pointer to Marker DPMK Marker Amplitude MAMPL MKR CENTER MCEN 1 2 MEXCHG FREQ ENTRY MFREQ CENTER MARKER FREQUENCY MKTIME Marker to Display Pointer MKDP Marker Location MLOCAT MKR REF LVL MTOP Tune Marker HRAMPL Next Higher Amplitude Next Lower Amplitude LRAMPL Marker Bandwidth Number BWNUM BANDWIDTH BWMODE Marker Peak Find MFBIG Marker Left Next MLFTNX PEAK FIND PKFIND Marker to Maximum and Center PKCEN Move Marker to
198. nd the spectrum analyzer defaults to the minimum span INC The next larger span division is selected in the front panel 1 2 5 sequence if possible DEC The next smaller span division is selected in the front panel 1 2 5 sequence if possible MAX The entire frequency range in use is swept Macro Memory Used 5 bytes Examples SPA 200 SPAN 50KHZ SPA 100 MHZ SPAN DEC Range Minimum value 10 Hz maximum value for direct entry given in Table 4 2 The maximum vale for INC or DEC is the 1 2 5 step that is less than or equal to the value in Table 4 2 INC and DEC will default to max imum or zero respectively when they reach the end of the range If the entry is out of range execution error message 31 is issued Power up value Maximum Interaction Changing the SPAN setting turns ZEROSP OFF and MXSPN OFF 4 12 SPAN frequency span division query Response to SPAN query ZEROSP zero span mode command CD CORON We ON The instrument is converted to a time domain mode with the frequency sweep defeated Crt readout shifts to the TIME DIV mode on the horizontal axis instead of FREQ SPAN DIV The previous FREQ SPAN DIV is saved and it is restored when ZEROSP is turned OFF OFF ZEROSP is cancelled leaving the FREQ SPAN DIV at the value previously selected T Macro Memory Used 2 bytes Power up value Off Interaction Changing the SPAN setting turn
199. ne as the last data byte is transferred The EOI line is also asserted with the ATN line true if the controller con ducts a parallel polling sequence on the bus The EOI line is not used for a serial polling sequence INTERFACE FUNCTIONS AND MESSAGES The ten major interface functions listed in Table A 1 provide a variety of capabilities and options for an instru mentation system These functions may be implemented in or for any particular instrument with instrument hardware or with a programming routine software Only those functions necessary for an instrument s purpose need be implemented by the instrument s designer it is not likely that one single instrument will have all ten interface functions For example an instru ment generally doesn t need to implement the Parallel Poll PP function if the instrument can respond to a serial polling sequence from the controller in charge of the GPIB system The following discusses the interface functions and their relationship to the interface control messages shown in Figure A 3 All the interface control messages discussed are sent and received over the GPIB with the ATN line asserted low RL Remote Local Function The RL function provides an instrument with the capability to select between two sources of input infor mation This function indicates to the instrument that its internal device dependent functions are to respond to information input from the front panel Local or
200. ned off When either marker is assigned to a new trace using the MTRACE command both markers assuming delta markers are on will move together In frequency mode marker operation the secondary marker remains at a constant frequency while the pri mary marker remains at a constant horizontal location However in the time mode both markers remain at con stant horizontal positions as the sweep speed is changed In the frequency mode the secondary marker can be tuned off screen while in the time mode the secondary marker cannot be tuned off screen The MFREQ command and the MFREQ and MLOCAT queries refer to frequency while ZEROSP is on The MKTIME command and query that set and read the marker time are only valid with ZEROSP ON and ZETIME ON any other use will result in a marker execu tion error message being issued An attempt to set a time that would be off either the left or right of the screen will cause a marker execution error message to be issued The MKTIME query will return 200 if the time value is unavailable 200 if ZEROSP is OFF or ZETIME if OFF and 999 99 if the marker system is off or MARKER is not set to DELTA when the secondary or delta time is requested Most of the frequency related marker functions remain frequency related while ZEROSP is on For instance frequency entry with the MTUNE command still enters frequency The STEP command still refers to fre quency and the PSTEP and MSTEP commands still
201. nimum span 49 FREQ change caused EXMXR change 50 SPAN defaulted to MAX 52 UNCAL light turned on 53 Multiple use of display buffer 54 UNCAL light turned off 110 STEP size out of range set to maximum 111 SPAN defaulted to minimum span Internal Errors System error Tuning DAC operation failed Failed to lock 1st LO Lost 1st LO lock Recentering failure on unlocking of 1st LO Calibration failure Battery operated RAM checksum error 1st LO tuning system failed 1st LO tuning system recovered from a failure 2nd LO tuning system failed 2nd LO tuning system recovered from a failure Phase lock system failed Phase lock system recovered from a failure IF count failed IF count recovered from a failure Power supply out of regulation Power supply regained regulation Frequency reference unlocked Frequency reference re locked 57 Tuning DAC carry operation failed 58 Failed to lock 1st LO 59 Lost 1st LO lock 60 Recentering failure on unlocking of 1st LO 61 Calibration failure 62 Battery operated RAM checksum error 72 1st LO tuning system failed 74 2nd LO tuning system failed 75 Phase lock system failed 78 IF count failed aif this error message is issued the macro in progress will be aborted System Commands and Queries 494AP Programmers ERROR EVENT Code 130 Table 9 4 Continued Meaning Internal Errors Continued Power supply out of regulation Frequency reference unlocked 1st LO tuning system recovered
202. nnector and cable assembly ensures that GPIB compatible instru ments can be physically linked together with complete pin compatibility The connector has 24 pins sixteen active signal lines seven interlaced grounds and 1 shield connection Standard connector pin arrangement and nomenclature for the digital control signals are illus trated in Figure A 1 The cable that attaches to the GPIB connector must be no longer than 20 meters maximum with no more than fifteen peripheral devices including a GPIB controller connected at one time The interconnecting cable assem bly which is offered as an optional accessory to the spectrum analyzer is provided with both a plug and receptacle connector type at each end of the cable to allow either a star or linear bus structure Contact your local Tektronix Field Office or representative for cable ordering information Connectors may be rigidly stacked using standard counter bored captive screws ELECTRICAL ELEMENTS The voltage and current values required at the con nector nodes on the bus are based on TTL technology The power source is not to exceed 5 25 V referenced to logic ground The standard defines the logic levels as follows Figure A 1 IEEE Std 488 GPIB connector 1 Logical 1 is a true state low voltage level lt 0 8 V signal line is asserted 2 Logical O is a false state high voltage level gt 2 0 V signal line is not asserted Messages can be sent over t
203. normal 1 normal 0 condition SRQ is asserted depends on RQS and EOS commands 5559 15 INTERFACE MESSAGES DCL 20 Clears OPI O buffer and status byte GET 8 Aborts and then rearms sweep GTL 1 Go To Local control IFC IFC line Initializes Talker and Listener Functions LLO 17 Local Lockout PPC 5 Parallel Poll Configure PPU 21 Parallel Poll Unconfigure SDC 4 Same as DCL if listener addressed SPD 25 Serial Poll Disable SPE 24 Serial Poll Enable TCT 9 Take Control Appendix B 494AP Programmers ERR EVENT RESPONSES ERROR Code Meaning 0 No error Command Errors 1 Illegal numeric format 4 END received in block binary 5 Block binary checksum error 6 Illegal placement of question mark 7 Query not recognized 8 Header not recognized 9 End of message unit not expected arguments missing 10 Character argument not allowed 11 Numeric argument not allowed 12 String argument not allowed 13 Binary argument not allowed 14 Link not allowed for this argument 20 Special argument type not recognized 21 Special argument not allowed 22 Character argument not recognized 24 Input buffer overflow Execution Errors 26 Output buffer overflow remaining output lost 27 Attempt to execute command in Local mode 28 Frequency out of range FREQ TUNE FIRST SECOND MMAX MMIN MTUNE MFREQ STSTOP STEP 29 FRQRNG out of range 30 CRES out of range 31 SPAN out of range 32
204. nput is chosen and dBm is automatically selected when the 50 0 input is chosen The units designator can be over ridden once the input selection has been made 4 17 Instrument Control 494AP Programmers RLUNIT reference level units query Response to RLUNIT query ROFSET reference level offset command 6 gt NUM This sets the offset that will be applied to the reference and marker levels Macro Memory Used 3 bytes Examples ROF 26 ROFSET 30 DB ROF 7 5DB Range 30 0 dB to 30 0 dB Power up value 0 dB Interaction The offset value will affect the responses to the queries of REFLVL MAMPL MLOCAT MAXPWR and THRHLD ROFSET must be included in the values sent with the REFLVL THRHLD and MAXPWR commands ROFSET reference level offset query Response to ROFSET query JTD 4 CAL command NOTE The instrument assumes a 100 MHz calibra tor is connected during CAL AUTO CAL AMPL and CAL LOG operation NUM 0 AUTO 1 LOG 2 AMPL 3 HPOS 4 VPOS CAL without arguments CAL AUTO The reso lution bandwidth filter frequencies are calibrated with respect to 10 MHz and levels relative to the 3 MHz filter level within a range of 2 4 dB and bandwidths used in dB Hz normalization are measured During operation the word MEASURING appears on the screen cali bration results are stored in battery powe
205. nput output statements in your controller s language and you re on your way Of course your controller must han die details such as asserting REN unaddressing bus devices and addressing the spectrum analyzer to start communication but these are steps taken by most con trollers when executing a GPIB 1 0 statement We have included some sample programs and exer cises adapted for the TEKTRONIX 4041 System Con troller Notes on the Program Examples Many combinations of languages and controllers may be used for programming the spectrum analyzer over the GPIB The examples in this manual are given in the BASIC language specifically in the version of BASIC used by the Tektronix 4041 System Controller Other ver sions of BASIC will probably have similar syntax Some controllers may require additional statements to set up data transfer over the GPIB For example 4041 BASIC contains optional OPEN and SET DRIVER state ments that set GPIB communications parameters These statements are not included in the program examples because the default parameter values are suitable for simple programs such as the examples The statements may be helpful in writing programs that involve multiple I O channels such as tape files Refer to the manual of the controller you are using for the statements needed in your application In these examples the spectrum analyzer s primary address is assumed to be 1 See Section 1 of this manual for instruction
206. nstrument Control 494AP Programmers In the CAL response the same data is given in suc cession for the 3 MHz 1 MHz 100 kHz 300 kHz for Option 07 instruments 10 kHz 1 kHz 100 Hz and 10 Hz filters in that order The data given for each filter is the following e frequency error e frequency calibration code level error level calibration code noise bandwidth factor bandwidth calibration code The frequency error is the difference between the measured filter frequency and 10 MHz expressed in Hz The level error is the difference between the measured filter level and the measured level of the 3 MHz filter expressed in dB The noise bandwidth is expressed as the dB correction used to normalize the filter s output to 1 Hz Use Table 4 5 to decode the calibration code numbers Table 4 5 CALIBRATION CODES Code Number Description 0 A calibration value for this item has not been found i e this filter has never been calibrated before This will always be returned for the 10 Hz filter noise bandwidth factor 1 A calibration value for this item has been found but the most recent calibration attempt failed the last previously good value is used Table 4 5 Continued CALIBRATION CODES Code Number Description 2 The value recorded for this item is the limit value i e the best it could do The actual required correction would exceed the limit 2 4 dB so this item is not calibrated
207. nt on the line held in variable 5 line 7 indented 15 spaces from the left The information to be printed will be 6 characters of the contents of the X register in decimal format to 1 digit followed by DBM units designa tor Line 320 Enter the contents of variable 2 into the X register Line 330 Subtract the contents of the Y register harmonic amplitude from the contents of the X register funda mental amplitude The result is put in the X register Line 340 Again print on the line held in variable 5 line 7 but indented 33 spaces from the left The information to be printed will be 6 characters of the contents of the X register in decimal format to 1 digit Line 360 Print NO SIGNAL on the line held in variable 5 indented 6 spaces Line 380 Go to the next harmonic number Line 390 Display the macro readout buffer Line 400 Tune back to the fundamental frequency Line 420 Print NO SIGNAL FOUND on the fourth line of the screen indented 2 spaces Line 430 Print MACRO KILLED on the sixth line of the screen indented 10 spaces Line 450 The macro is done running Line 460 This is the end of the macro entry SOHOVM AIdANVS Appendix B 494AP Programmers HARMONIC TEST MACRO Continued STMAC 1 HARMONIC TEST Store as macro number 1 and title it HARMONIC TEST MARKER SINGLE Turn on a single marker RDOUT NORMAL Readout normal CLEAR Clear macro readout buffer SWEEP Do a swee
208. o ensure the correct response all of the VRTDSP LOG 2DB letters in each of the unit mnemonics for the VRT LOG 1 DB REFLVL command must be entered not just VRTDSP LIN the first three letters as required for other VRT LIN 2 mnemonics VRTDSP LIN 1 5MV VRT LIN 75 NV NUM The instrument sets the reference level to VRTDSP LIN INC the nearest dBm step for a log vertical display except in Range Log is 1 15 dBV the Delta Amplitude mode and to the nearest dBm step Lin is 39 6 nV div to 2 8 V div if the reference for a linear vertical display The Delta Amplitude mode level offset is zero allows 0 25 dB resolution the argument to the REFLVL command is always the absolute reference level not an 4 16 offset to the present reference level though the crt readout shows relative amplitude in the Delta Amplitude mode only If the number selected is out of range execu tion error message 34 is issued If no units are specified the instrument assumes the current reference level units INC or DEC The reference level is stepped up or down once The step value is determined by the value of the VRTDSP scale factor and FINE selection refer to Table 4 4 Macro Memory Used 4 bytes Table 4 4 REFERENCE LEVEL STEPS Scale Factor FINE ON FINE OFF 15 dB 1dB 15dB 14 dB 1dB t14dB 13 dB 1dB 13 12 dB 199 12dB 11 dB 199 10 dB 1dB 10dB 9 dB iB X 8 dB idB
209. o occur either at the end of every sweep or as needed based on the drift rate of the oscillators ON Oscillator corrections occur at the end of every sweep OFF The time between oscillator corrections is determined by the drift rate of the oscillators Interaction When ECR is ON corrections will gen erally occur more frequently than when ECR is OFF The extra time spent correcting the oscillators may lengthen the response time to other commands and queries 4 36 Macro memory used 2 bytes Power up value OFF ECR query ECR a Response to ECR query SSR send service request command The SSR command asserts SRQ The status byte will report this as an internal error warning and system event number 140 will be returned Interaction The service request will be asserted only if RQS is ON Macro Memory Used 2 bytes There is no SSR query RVALID register valid query YES is returned if the indicated register contains a valid front pannel setting or display and NO is returned if it does not Examples RVALID FPSET 2 RVA FPS 7 RVA DISP 7 Range 0 9 if FPSET is used and 0 8 if DISP is used Response to RVALID query Interaction If HDR is OFF thed register type register number and separators are eliminated along with the header If the register number is out of range the value 1 is substituted for the register number in the response assuming HDR is
210. of all preceding bytes except the first 9e Thus the modulo 256 sum of all bytes except the first should equal zero to provide an error check of the binary block transfer 7 4 BINARY BLOCK END BLOCK END BLOCK End block is a sequence of binary numbers that is preceded by the ASCII code for at EOI must be asserted concurrently with the last data byte The end block can only be the last data type in the message The CURVE command cannot be used within a macro Examples CURVE CRVID FULL 100 100 101 99 996 more numbers CURVE 500 or 1000 numbers CUR BINARY BLOCK Interaction A waveform sent in a CURVE com mand is overwritten in the display I O buffer if preceded by a CURVE query in the same message This causes the queried display data to be put back into digital storage CURVE display curve query Response to CURVE query re Lc 9 0 Waveform data is related to the display by Figure 7 1 DISPLAY UNITS REFERENCE LEVEL TOP OF CRT GRATICULE 250 300 350 400 450 500 400 500 600 700 800 900 1000 RRAY POINT NUMBER A OR B 1 TO 500 FULL 1 TO 1000 Figure 7 1 Waveform data related to the display WAVFRM waveform query The WAVFRM query response is the same as the response to WFMPRE CURVE The most recent WFID and CRVID arguments select whether A B or both memories are selected for data transfers and waveform processing in ASCI
211. om modate most other controllers A change in this switch takes immediate effect 1 3 Introduction to GPIB Operation 494AP Programmers LF OR 1 2 9944948 op _ 1 OUTPUT A SWITCH DOWN Set for use with Tektronix controllers LF OR 4 385858949 OUTPUT LF amp EOI B SWITCH UP 5559 13 Figure 1 4 Effect of message terminator switch for Input and output 1 4 Setting the TALK ONLY and LISTEN ONLY Switches The spectrum analyzer switches for talk only and listen only operation are part of the GPIB ADDRESS switch bank shown in Figure 1 3 Either or both switch is on when it is in the up or 1 position and either is off in the down or 0 position If instrument power is on press RESET TO LOCAL or blue SHIFT PLOT for a change in these switches to take effect Both the TALK ONLY and LISTEN ONLY switches must be off when the spectrum analyzer is used with any controller As contrast both switches must be on to allow spectrum analyzer output to be exchanged with a storage device without the need of a controller The TALK ONLY switch must be on to allow spectrum analyzer output to be sent to a plotter With the LISTEN ONLY switch on information sent to a storage device can be fed back to the spectrum analyzer IEEE 488 FUNCTIONS The spectrum analyzer is compatible with IEEE STD 488 1978 The connector and the signal levels at the con nector follow the specif
212. ommands only instru ments previously addressed to listen will respond to these commands universal commands all instruments whether they have been addressed or not will respond to these commands and secondary addresses for dev ices interfaced through a primary instrument Parallel Poll Enable PPE messages are derived from the characters in the first column under Lower Case letters in Figure A 3 decimal coded characters 96 through 111 The standard recommends the use of decimal code 112 lower case letter p for the Parallel Poll Disable PPD command All parallel poll configured instruments respond with status information at the same time when the EOI line is asserted with ATN true Table A 2 INTERFACE MESSAGES REFERRED TO IN THIS APPENDIX AND FUNCTIONS Interface Mnemonic Message Function Remote Messages Received Attention AH C L LE PP SH T TE DAC Data Accepted SH DAV Data Valid AH DCL8 Device Clear DC GET Group Execute Trigger DT Go Local RL IFC Interface Clear CL LE T TE LLOa Local Lockout RL MSA My Secondary Address LE TE MTA My Talk Address LIE Parallel Poll Configure PP PPDa Parallel Poll Disable PP PPE Parallel Poll Enable PP PPU Parallel Poll Unconfigure REN Remote Enable RL RFD Ready For Data SH 0 Selected Device Clear DC SPD Serial Poll Disable LIE SPE Serial Poll Enable LIE SRQ Service Request via C TCT Take Contro
213. on is not apparent unless the transformed data is output over the GPIB or loaded into digital storage because of either of the conditions noted in part 2 For further information refer to Multiple Use of Display Buffer for Waveform Processing and 1 0 in Sec tion 10 of this manual CENSIG center signal command This command TUNES the frequency to center the signal represented by the display data point or as close as possible given the specified span accuracies This command does not get a new display data point or digital storage waveform Therefore if a new waveform is acquired after CENSIG is run the display data point may no longer match the signal of interest Macro Memory Used 1 byte Waveform Processing 494AP Programmers TOPSIG move to top of graticule command This command changes REFLVL to move the signal represented by the display data point to the reference level or as close as possible given the specified vertical display and reference level accuracies This command does not acquire a new display data point or digital storage waveform Therefore if a new waveform is acquired after TOPSIG is run the display data point may no longer match the signal of interest Macro Memory Used 1 byte There is no TOPSIG query 8 3 Section 9 494AP Programmers SYSTEM COMMANDS AND QUERIES Spectrum analyzer device dependent message units are provided to set and return parameters of use to the con
214. on it While busy acting on the message the spectrum analyzer does not accept any other device dependent messages When it is finished with the message the spectrum analyzer is ready to handshake another mes sage which it then acts on and so forth You can depend on the spectrum analyzer to assert NRFD on the GPIB while it is busy this prevents a controller GPIB output statement that would send further instructions to the spectrum analyzer For example enter 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Fori 1 to 10 110 Print z FREQ i QHZ 120 Nexti Watch the spectrum analyzer FREQUENCY readout change while this loop is executing You can see that the controller executes the loop more slowly than it would if line 110 only printed what is in quotes on the controller crt What is making the controller step through the loop at a more deliberate pace It must wait at line 110 for the spectrum analyzer to execute the previous FREQ command A controller GPIB input statement can also be used to synchronize the controller and the spectrum analyzer The controller could make a table of frequency ranges for the frequencies covered by the previous loop filling the table only after the FREQ command is executed 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Dim f 10 2 110 Fori 1 to 10 120 Print z FREQ 5i GHZ FRORNG 130 Input 2 1 1 1 140 f 1 2 i 1E 9 150 Nexti 10 2 Line 130 Addresses the spectrum analyzer to tal
215. one program line MATH COMMANDS The math commands add the X and Y registers PLUS subtract the X register from the Y register SUBT multiply the X and Y registers MULT and divide the Y register by the X register DIVIDE In case of an overflow the result in XREG is set to the maximum value PLUS add X and Y registers command The PLUS command adds the contents of XREG to the contents of YREG and puts the result in XREG e g XREG XREG Macro Memory Used 1 byte Range of Result 9 999 999 999 999 99 to 9 999 999 999 999 E 99 Interaction The YREG is unchanged after the PLUS command There is no PLUS query SUBT subtract X from Y register command The SUBT command subtracts the contents of XREG from the contents of YREG and puts the result in XREG e g XREG YREG Macro Memory Used 1 byte Range 9 999 999 999 999 E 99 to 9 999 999 999 999 E 99 Interaction The YREG is unchanged after the SUBT command 6 1 Macros 494AP Programmers There is no SUBT query MULT multiply X and Y registers command The MULT command multiplies the contents of XREG with the contents of YREG and puts the result in XREG e g XREG XREG x Macro Memory Used 1 byte Range 9 999 999 999 999 E 99 to 9 999 999 999 999 E 99 Interaction The YREG is unchanged after the MULT command There is no MULT query DIVIDE d
216. only OO o e ON The 75 Q input is used If Option 07 is not installed command error message 8 will be issued OFF The 50 Q input is used Macro Memory Used 2 bytes Power up value OFF IMPED impedance query Option 07 only Response to IMPED query Option 07 only CD OEO Instrument Control 494AP Programmers FREQUENCY SPAN AND RESOLUTION The commands in this group control the frequency span SPAN the zero span mode ZEROSP the max span mode MXSPN and the resolution RESBW and ARES of the display Also true signals can be distinguished from spuri ous frequency conversion products IDENT AREs IDENT ATICAL VIDEO D DISPLAY FILTER ST wot view RESOLUTION BANDWIDTH VERT SPLAY RF INPUT 500 TO 21 0s MAR TIME DIV POSITION CAL OUT Figure 4 2 Front panel Frequency Span and Resolution commands 4 11 Instrument Control 494AP Programmers SPAN frequency span division command NUM The span division is selected The value of the argument is rounded to two significant digits Zero converts the instrument to the time domain in zero span mode the instrument displays signals within its bandpass RESBW about its center frequency FREQ If the number is too large execution warning message 50 is issued and the instrument defaults to MAX If the number is too small execution warning message 111 is issued a
217. onse to ZETIME query 4 5 19 The macroinstruction macro commands in this sec tion are divided into the seven categories of math regis ter branching and looping print data and general com mands The branching and looping commands are avail able only within macros they cannot be used outside of macros Prepare your macros using a language such as BASIC and a controller Once the macro is stored in the spectrum analyzer memory it can be run at any time without the further use of a controller We recommend that a copy of all macros be kept for ease in reconstruct ing a macro if it is lost Any stored macros will be lost if the battery power to the memory is interrupted as when the battery is removed for long term storage If any GPIB command arrives over the bus while a macro is running the macro is stopped The RUN com mand or RUN STOP from the front panel will restart the macro A GPIB query has no affect on macros There are 8 k bytes of memory dedicated for macro use Although there is no set limit for each macro it is important that you know the number of bytes used for each command and keep this in mind while preparing macros The number of bytes used for each command is included with the commands in this section and there is also a table in the pullout pages at the back of this manual that lists all available spectrum analyzer com mands and the bytes used by each Notes on the Program Exa
218. or listen only mode it can only communicate with other devices on the bus when it is enabled to do so by the controller in charge of the instrumentation system A controller is an instrument that determines by software routines which instrument will talk and which instruments will listen during any given time interval The controller has the ability to assign itself as a talker or a listener whenever the program routine requires it In addition to designating the current talker and listeners for a particular communication sequence the controller is assigned the task of sending special codes and com mands called interface control messages to any or all instruments on the bus A complete operating system may contain more than one controller The IEEE standard has provisions for a system controller that operates with another controller in charge of the bus The controller that is in charge of the bus can take control only when it is directed to do so by the system controller The system controller itself may be but is not necessarily the con troller in charge of the bus INTERFACE CONTROL MESSAGES The two types of interface control messages are multi line messages sent over the data bus and uni line messages A message that shares a group of signal lines with other messages in some mutually exclusive set is called a multi line message only multi line message mes sage byte can be sent at one time A message sent over
219. or less in bands 6 12 for the identify function to operate The SIGSWP commands cause alternating normal and vertically offset sweeps the first sweep is normal the next offset and so on If SGTRAK is on execution error message 101 is issued if IDENT is ON and the command is not executed IDENT identify query CoE pH Response to IDENT query Instrument Control 494AP Programmers VERTICAL DISPLAY AND REFERENCE LEVEL The commands in this group control the vertical scale factor VRTDSP and reference level REFLVL and FINE of the display and select the reference level units RLUNIT and the reference level offset ROFSET The gain distribution combination of RF attenuation and IF gain is automatically set according to the reference level mode RLMODE this takes into account the least amount of RF attenuation MINATT allowed or maximum power MAXPWR expected and the current RF attenuation is requested RFATT The reduced gain mode RGMODE enables 10dB of IF gain and RF attenuation reduction when in 10 dB division The largest signal in a window around the display data point can be peaked PEAK The pulse stretcher PLSTR stretches narrow or pulsed signals for acquisition and display If a video filter VIDFLT is switched in noise in the display is reduced Calibration of the IF filters for frequency and amplitude is possi ble from the front panel CAL and ENCAL 4904AP 9 LI i g FREQUENCY gt
220. ormat is shown below Query Response Format A query readies the spectrum analyzer for output In query responses the response header can either be returned with the response or not returned this depends on whether the header command HDR is turned ON or OFF The output message format in response to a mode or parameter query is as follows Device Dependent Message Structure and Execution 494AP Programmers SPECTRUM ANALYZER OUTPUT MESSAGES When the spectrum analyzer executes a query it buffers an output message unit that is a response to the query Output message units contain ASCII characters except when binary data is requested Output Message Format The output message unit combines the header and appropriate argument s Message units are combined if the output includes a response to the SET query or to more than one query The header for query responses can either be turned on or off Output Message Execution The spectrum analyzer begins output when talked and it continues until it reaches the end of the informa tion in its buffer or is interrupted by a DCL Device Clear UNT Untalk or IFC Interface Clear message If the spectrum analyzer is interrupted and the buffer is not cleared the spectrum analyzer will resume output if it is retalked The buffer may be cleared by the DCL mes sages or if it is listened by the SDC message or any device dependent message If not interrupted
221. owed 12 String argument not allowed 13 Binary argument not allowed 14 Link not allowed for this argument 20 Special argument type not recognized 21 Special argument not allowed 22 Character argument not recognized 24 Input buffer overflow 26 Output buffer overflow remaining output lost 27 Attempt to execute command in Local mode 28 Frequency out of range FREQ TUNE FIRST SECOND MMAX MMIN MTUNE MFREQ STSTOP STEP 29 FRQRNG out of range 30 CRES out of range 61 SPAN out of range 32 RESBW out of range 33 MAXPWR or MINATT out of range 34 Level out of range REFLVL THRHLD BWNUM MVRTDB MVLFDB 35 VRTDSP LIN out of range 36 VRTDSP LOG out of range 37 TIME out of range 39 IDENTify not allowed in this span div 40 Signal finds not allowed in zero span 41 Invalid DATA or ADDR argument contents 42 DATA direction not compatible with ADDR direction 45 GET Group Execute Trigger ignored not executed 46 NUMEV out of range STORE RECALL DSTORE DRECAL or RDATA out of range 49 FREQ change caused EXMXR change 50 SPAN defaulted to MAX 52 UNCAL light turned on 53 Multiple use of display buffer 54 UNCAL light turned off 57 Tuning DAC carry operation failed 58 Failed to lock 1st LO 59 Lost 1st LO lock 60 Recentering failure on unlocking of 1st LO 61 Calibration failure 62 Battery operated RAM checksum error 72 1st LO tuning system failed 74 2nd LO tuning system failed 75 Phase lock sys
222. ows the controller in charge to start the basic operation specified for an instrument or group of instruments on the bus The IEEE 488 standard does not specify the basic operation an instrument is to perform when it receives the GET Group Execute Trigger command To issue the GET command the controller asserts ATN sends the listen addresses of the instruments that are to respond to the trigger and then sends the GET message Once an instrument starts its basic operation in response to GET the instrument must not respond to subsequent trigger state transitions until the current operation is complete Only after completing the opera tion can the instrument repeat its basic operation in response to the next GET message Thus the basic operating time is the major factor that determines how fast the instrument s can be repeatedly triggered by commands from the bus A 9 IEEE STD 488 GPIB System Concepts 494AP Programmers C SR and PP Controller Service Request and Parallel Poll Functions The C Controller function provides the capability to send primary talk and listen addresses secondary addresses universal commands and addressed com mands to all instruments on the bus The Controller func tion also provides the capability to respond to a service request message SRQ from an instrument or to conduct a parallel poll routine to determine the status of any or all instruments on the bus that have the Parallel Poll P
223. p MFBIG Put marker on highest signal IF SIGNAL Do harmonic test if signal was found PRINT 1 1 HARMONIC TEST Print title PRINT 3 1 FUNDAMENTAL FREQUENCY AMPLITUDE ENTER MFREQ Enter primary frequency into register STNUM 3 Store fundamental frequency PRINT 4 1 XREG FFORMT 18 0 Display fundamental frequency ENTER MAMPL Enter primary amplitude into register STNUM 2 Store fundamental amplitude PRINT 4 28 XREG DEC 6 1 Display fundamental amplitude PRINT 5 1 M PRINT 6 1 HARM tst LEVEL DBC STEP PRIMAR Put marker frequency into step size FOR 1 1 10 For 1 1 to 10 ENTER 6 ENTER VAR 1 PLUS Add 6 to loop counter STNUM 5 Store display line number PRINT VAR 5 2 VAR 1 DEC 2 0 Display harmonic number PSTEP Plus step SWEEP Do a sweep MF BIG Put marker on highest signal IF SIGNAL If signal then display level ENTER MAMPL PRINT VAR 5 15 XREG DEC 6 1 DBM Display harmonic level ENTER VAR 2 Enter fundamental amplitude SUBT Xreg fundamental amplitude harmonic amplitude PRINT VAR 5 33 XREG DEC 6 1 Display dbc level ELSE PRINT VAR 5 6 NO SIGNAL gt Display no signal ENDI NEXT Next harmonic number TEXT MACRO Display macro readout buffer ENTER VAR 3 Enter fundamental frequency PUTREG FREQ Tune back to fundamental frequency ELSE DSLINE 4 BOTTOM Display normal top and bottom readout and line 4 in the ma
224. pace from the left Line 180 Enter the current marker frequency into the X register Line 190 Print the following on the fourth line of the screen beginning 1 space from the left 18 characters of the contents of the X register in frequency format to 0 resolution Line 200 Enter the current marker amplitude into the X register and store this information into variable number 2 Line 210 Print the following on the fourth line of the screen beginning 28 spaces from the left 6 characters of the contents of the X register in decimal format to 1 digit Line 220 Print a separating line on the fifth line of the screen beginning 1 space from the left Line 230 Print the current harmonic information on the sixth line of the screen beginning 1 space from the left Line 240 Put the marker frequency into step size Line 250 For variable 1 1 to 10 Line 260 Enter 6 into the X register enter the contents of variable 1 into the X register copying the 6 to the Y register add 6 to the loop counter and store the display line number Line 270 Print the contents of variable 1 on the fifth line of the screen beginning 2 spaces from the left This infor mation will be 2 characters printed in decimal format to O digits Line 280 Set plus step do a sweep and put the marker on the highest signal Line 290 If a signal is present display the level Line 300 Enter the marker amplitude Line 310 Pri
225. ps can be accomplished by a statement such as Getting Started 494AP Programmers input prompt RES VID s z p EXERCISE ROUTINES Talk Listen Now let s put the statements for message 1 0 together to exercise the spectrum analyzer as a listener and a talker This routine is handy because it waits for your input and sends it time after time If the spectrum analyzer responds with a message the message is printed before another message is requested from you Enter any of the commands or queries described in Sec tions 4 through 9 of this manual An SRQ handler is included in the routine to print out any error messages The following routine makes use of one of the friendly features of the spectrum analyzer When the spectrum analyzer is talked with nothing to say it outputs a byte with all bits set to one and asserts EOI The routine doesn t have to search the output character string for a a query and branch to input the response Instead the response is read after every message and printed a blank line if the spectrum analyzer sends a byte with all ones The SRQ handler uses another spectrum analyzer feature Rather than print a code for the status byte the routine asks for the error that caused the SRQ ERR This offers much more specific information about the problem The meanings of the error and event codes are listed in Table 9 3 in Section 9 of this manual The routine assumes you have assigned the value of
226. r The peak code consists of numbers at 500 MHz intervals when using the preselector and one number per band when using external mixers These numbers are stored in memory If a signal is not found within the window the previously acquired peaking code stored in memory is used End of sweep interrupts are not issued and the TRIGGERING TIME DIVISION MAX HOLD and REFLVL values may be changed by the spec trum analyzer while PEAK is active The previous values are restored when PEAK AUTO is through Although this command uses digital storage it does not overwrite the A portion if SAVEA is ON The PEAK command without an argument is the same as PEAK AUTO NUM The number is stored in memory Non integers or numbers outside the range are rounded to the nearest integer in the range no warning 1 issued This affects the current peaking number only Range 0 to 1023 INC or DEC The value of PEAK is changed 1 from its current value which is stored in memory and the new value is stored in memory KNOB The front panel MANUAL PEAK control is active You can manually peak the spectrum analyzer s response from the front panel All other arguments switch to internal peaking and cancel KNOB STORE The value stored in memory is used for the present band with internal mixer in bands 2 5 or frequency with external mixers or preselector MARKER PEAK MARKER acts the same as PEAK AUTO except PEAK MARKER will peak
227. r frequency by using the value of the command argument as an offset to its previous center frequency Macro Memory Used 6 bytes Examples TUN 10 MHZ TUNE 1 0E6 TUNE 100 KHZ Range The frequency resulting from using the TUNE command must be within the frequency range in use The maximum value for each freuqency range that is the value needed to tune from one end of the range to the other is given in Table 4 2 There is no TUNE query TMODE set tune mode command MARKER The PSTEP and MSTEP commands will change the marker frequency FREQ The PSTEP and MSTEP commands will change the center frequency NUM 0 FREQ 1 MARKER Power up value FREQ Macro Memory Used 2 bytes Interaction If MARKER is OFF TMODE MARKER sets MARKER to SINGLE TMODE sets the tuning mode that the front panel CENTER MARKER FREQUENCY knob will have when the analyzer is returned to local control TMODE tune mode query Response to TMODE query FIRST 1ST LO frequency command COLOS NUM The instrument 1ST LO is set to the requested frequency The resulting center frequency will be displayed Macro Memory Used 6 bytes Examples FIR 2 8 GHZ FIRST 2 8 GHZ Range Refer to Table 4 2 Power up value 2072 MHz FIRST 1ST LO frequency query Response to FIRST query CS ag 2 ER SECOND 2ND LO frequency command SECOND w SP NUM s NUM
228. r other universal 3 4 commands are 17 for LLO local lockout 21 for PPU parallel poll unconfigure 63 for UNL unlisten and 95 for UNT untalk Addressed commands such as GTL go to local can also be sent to the spectrum analyzer The codes for the addressed commands are 1 for GTL 4 for SDC selected device clear 5 for PPC parallel poll configure and 8 for GET group execute trigger GET causes the spectrum analyzer to stop the current sweep and immediately start another sweep synchronizing data acquisition with the interface message When the IFC interface clear line is asserted by the controller the spectrum analyzer talker and listener func tions are initialized same effect as UNT and UNL Use the WBYTE statement to send the universal commands For example use this 4041 statement to send a device clear message on the bus 100 WBYTE DCL For addressed commands include the primary address of the programmable spectrum analyzer being talked to For example this 4041 statement sends a go to local command to the spectrum analyzer at address 3 100 GTL 3 Acquiring a Waveform The waveform in digital storage can be requested as either ASCII coded decimal numbers or a block of binary data To keep this simple let s discuss the ASCII here and cover the binary with the WFMPRE command in Sec tion 8 of this manual When power is first applied to the spectrum analyzer it is ready to transmit wavefor
229. red memory CAL LOG The instrument is set up so you can set the front panel CAL LOG adjustment CAL LOG has an indefinite execution time and will operate until either a device clear DCL is received from the GPIB port or the spectrum analyzer is returned to local control from the instrument front panel An instruction message appears on the screen CAL AMPL The instrument is set up so you can set the front panel CAL AMPL adjustment CAL AMPL has an indefinite execution time and will operate until either a device clear DCL is received from the GPIB port or the spectrum analyzer is returned to local control from the instrument front panel An instruction message appears on the screen CAL HPOS The instrument is set up so you can set the front panel horizontal POSITION control CAL HPOS has an indefinite execution time and will operate until either a device clear DCL is received from the GPIB port or the spectrum analyzer is returned to local control from the instrument front panel An instruction message appears on the screen CAL VPOS The instrument is set up so you can set the front panel vertical POSITION control CAL VPOS has an indefinite execution time and will operate until either a device clear DCL is received from the GPIB port or the spectrum analyzer is returned to local control from the instrument front panel An instruction message appears on the screen CAL query CAL Response to CAL query I
230. red when multiband sweep is exited If there is a waveform in SAVEA it will be automatically overwritten SAVEA and MXHLD operate normally Since only the A waveform is displayed SAVEA ON stops display updating e Displays may only be stored and recalled into the A register If the B display is requested with the DRE CAL or DSTORE command execution error mes sage 140 will be issued and no display will be recalled e f the multiband mode is exited using either the MXSPN or ZEROSP commands the span saved will be the multiband span The span will return to this value or default to maximum when either the Max or Zero Span Mode is cancelled refer to the infor mation under Changing the span in Exiting Multiband Sweep for additional information The instrument will not return to the multiband mode The multiband frequency range displayed can only be changed by entering new start and stop frequen cies with the STSTOP command Changing the span with the SPAN command or directly entering a center frequency with the FREQ command exits the Multiband Sweep mode Markers may be tuned over the displayed range only The marker system treats the multiband display as if it were a saved or stored display the tuning limits were mentioned previously The MCEN and PKCEN commands cannot be used e With the ARES ON command the resolution bandwidth used is the widest value required by the bands being swept If any of the bands is uncali
231. restored by the INIT command Refer to Section 9 of this manual for more on this command and a list of the initial power on settings 1 6 4415 07 Figure 1 6 The spectrum analyzer can be connected to GPIB system in either a star A or a linear B pattern Section 2 494AP Programmers DEVICE DEPENDENT MESSAGE STRUCTURE AND EXECUTION The goal of the programmable spectrum analyzer device dependent message structure is to enhance com patibility with a variety of GPIB systems yet be simple and obvious to use This goal is achieved within the framework of the Tektronix Interface Standard for GPIB Codes Formats Conventions and Features This standard is intended to make messages on the bus clear and uncomplicated while allowing the instrument to handle messages in a friendly manner i e to accept variations in the mes sage Compatibility with existing devices is maintained as much as possible while use of codes and data for mats is encouraged to make maximum use of bus capa bilities To make spectrum analyzer messages easy to under stand and write ordinary engineering terms are used Message codes mnemonics are chosen to be short yet remind you of their function For example to set the instrument center frequency to 500 000 MHz the mes sage FREQ 500 000 MHZ could be sent over the bus after the instrument has been addressed as a listener Variations on this message are allowed to make it s
232. rmal instrument readout is being displayed and not the macro readout buffer or text sent with the RDOUT command e Markers and digital storage must be on for the marker s to be plotted e The position of the marker s will be plotted out as an X VIEWA must be ON to plot the A waveform VIEWB must be ON to plot the B waveform and BMINA must be ON to plot the difference between the A and B waveform The readout settings currently displayed on the instrument are the only readout settings plotted e The plot can be in more than one color when using the Tektronix 4662 Opt 31 or the 4663 emulating the 4662 the HP7470A HP7475A HP7580B HP7585B or HP7586B or the Gould 6310 or 6320 The grati cule marker s and bezel information will plot in one color and the waveform in another color f the macro readout buffer is displayed it alone will plot e Refer to Using PLOT with Macros in the Macros sec tion of this manual for additional information The response to PLOT depends on the plotter in use refer to the select plotter command PTYPE for a description of the plotter selections Instrument Control 494AP Programmers NOTE Since the GPIB languages of the Tektronix 4662 Opt 01 4662 Opt 31 and 4663 Interac tive Digital Plotters the Hewlett Packard or the Gould plotters do not conform to the Tektronix Interface Standard for GPIB Codes Formats Conventions and Features this response does not fol
233. rned on NUM 0 OFF 1 ON or SINGLE 2 DELTA Macro Memory Used 2 bytes Power up value OFF Interaction MARKER SINGLE or ON or MARKER DELTA sets TMODE to MARKER MARKER OFF sets TMODE to FREQ MARKER SINGLE or MARKER DELTA are selected by most other marker commands MARKER marker mode query 5 1 Marker System 494AP Programmers Response to MARKER query a MTRACE allows either the Primary or Secondary marker to be placed on a trace location other than default MTRACE or MTRACE PRIMAR The Primary marker is set MTRACE SECOND The Secondary marker is set Use A B FULL or BMINA to place the selected marker on the designated trace Macro Memory Used 3 bytes Examples MTRACE B MTR PRI A MTRACE SECOND BMINA Power up value If the marker system is not turned on with the MTRACE command the marker location will be assigned according to the settings of the digital storage commands as shown in Table 5 1 Table 5 1 MARKER TRACE ORGANIZATION VIEW VIEW SAVE B SAVE PRIM SECOND A B A A MARK ON MARK ON of jor Jof ort FULL FULL of jor A Of Off On On B SAVEA B SAVEA Of of _ Full Of On On of B of On on B 5 2 Table 5 1 Continued MARKER TRACE ORGANIZATION VIEW VIEW SAVE B SAVE PRIM SECOND A B A MARK ON MARK ON On of jor jor On On lor
234. rom the macro readout buffer MRDO and print a number or a string PRINT CLEAR clear macro readout buffer command NUM Only the numbered line 1 to 16 the macro readout buffer will be cleared CLEAR without an argument or NUM greater than 16 will clear the entire macro readout buffer Macro Memory Used 2 bytes There is no CLEAR query DSLINE display line command C 9 0 20 6 9 Macros 494AP Programmers The DSLINE command affects the normal 3 line readout and displays the normal top line of crt readout the normal marker 2nd line of crt readout MARKER and the normal bottom line of crt readout BOTTOM TOP MARKER and BOTTOM must appear in the command line in the same position as they appear in the syntax diagram above If a line number is used instead of TOP MARKER or BOTTOM that line from the macro readout buffer is displayed The location of the line number in the command line does not matter If O is used as a line number that line will not be displayed the line will be blank If NUM is greater than 16 the normal readout is displayed On the screen the first eight lines are displayed then there is blank area about the width of two lines then the last eight lines are displayed If a line number is used more than once macro exe cution error message 169 will be issued Examples See Example Descriptions Below DSLINE 1 2 0 f See 1 DSLIN
235. rs imum digital storage points the marker is positioned here If as in Figure 5 2 the calculated center of the sig nal is not equal to the maximum digital storage point the marker is positioned on the closest point to the center At the end of this Marker Functions portion are five illus trations showing the use of this signal finding command To the finding routine a candidate signal consists of a peak above threshold and two points one on each side of the peak that are 3 dB below the peak The location of the candidate signal is the highest amplitude point on the signal Whether or not the candidate is recognized as a signal depends upon the processing mode chosen CLOSEST POINT TO CENTER RIGHT MOST PEAK 5557 26 Figure 5 2 Locating the signal peak When SPURS is chosen all candidates are taken to be signals When CW is chosen a signal to be a signal must be at least half as wide as would be predicted from the resolution filter in use Note that this is not the same algorithm as the one used by the data point related com mands In particular the data point algorithm looks for a particular width while the marker related algorithm looks only for a minimum width Note also that if the span is wide in comparison with the resolution bandwidth there may be no difference between SPURS and CW When PULSE is chosen if two candidate signals are within two minor divisions 0 4 of a major division they are assumed
236. rs are off when power is first turned on to the instrument When markers are turned on in zero span or the instrument is set to zero span with the markers on and ZETIME is set to ON the markers are placed at center screen and the time value is set accordingly Interaction MKTIME is available only when the instrument is in the zero span mode If MKTIME is used when the instrument is not in the zero span mode or ZETIME is OFF marker execution error message 107 is issued An attempt to set a time that would be off either the left or right of the screen will cause marker execution error message 108 to be issued MKTIME marker time query MKTIME or MKTIME PRIMAR The time is returned for the Primary marker MKTIME SECOND The time is returned for the Secondary marker MKTIME DELTA The time is returned for the Pri mary marker with respect to the Secondary marker 5 8 Interaction The MKTIME query will return 200 if the time value is unavailable 200 if the instrument is not in the zero span mode or ZETIME is OFF and 999 99 if the marker system is off or MARKER is not set to DELTA when the secondary or delta time is requested Response to MKTIME query Interaction If HDR is OFF PRIMAR SECOND or DELTA and the following delimiter are eliminated along with the MKTIME header MKDP marker to display pointer command The Primary marker is moved to the same horizontal location as the disp
237. rted concurrently with the last data byte or the ASCII code for line feed LF sent as the last data byte The active terminator is selected by the rear panel GPIB ADDRESS switch 3 Format Characters Format characters may be inserted at many points to make the message more intelligible but are required only if they are included as a literal element i e in circles or ovals with no bypass Allowable format characters are SP space CR carriage return and LF line feed unless the end of message terminator is set for LF as well as all other ASCII control characters and comma At some points in a message the spectrum analyzer may accept other non alphanumeric characters such as quo tation marks Input Buffering and Execution The spectrum analyzer buffers each message it receives with a capacity that exceeds that required for the SET response The spectrum analyzer waits until the end of the message to decode and execute it A command error in any part of a message prevents its execution When the instrument is under local control commands that would conflict with local control are ignored see Remote Local under IEEE 488 Functions in 2 2 Section 1 of this manual If the message contains multiple message units none are acted on until the instrument sees the end of message terminator When the spectrum analyzer sees the terminator it executes the commands in the mes sage in the order they were rece
238. ry marker or their difference MAMPL tune the Pri mary marker frequency to center screen MCEN track the Primary marker with the display pointer MCPOIN exchange the Primary and Secondary marker positions set the Primary marker frequency MFREQ move the Primary marker to the display pointer horizon tal location MKDP return the frequency and amplitude of the Primary or Secondary marker or their difference MLOCAT move the marker to the reference level MTOP and tune the Primary marker MTUNE DPMK display pointer to marker command The DPMK command moves the display pointer to the Primary marker position Macro Memory Used 1 byte Interaction DPMK cancels the WFID portion of any previous WFMPRE command or the CRVID portion of any previous CURVE command and selects the FULL waveform for data transfers and waveform processing If MARKER is OFF DPMK sets MARKER to SINGLE There is no DPMK query Marker System 494AP Programmers MAMPL marker amplitude query oom MAMPL or MAMPL PRIMAR The amplitude of the Primary marker is returned MAMPL SECOND The amplitude of the Secon dary marker is returned MAMPL DELTA The amplitude of the Primary marker with respect to the Secondary marker is returned NOTE If the marker whose amplitude is being requested or in the case of MAMPL DELTA the amplitude of either marker is out of the range of digital stora
239. s 494AP Programmers LABEL label point in macro command NUM Sets the reference point for the GOTO and GOSUB commands Macro Memory Used 2 bytes Range 1 to 100 There is no LABEL query FOR variable X to Y step Z command and NEXT The FOR command syntax diagram is on the next column NUM Identifies the variable The second argument indicates the starting variable value the third argument indicates the limiting value and the fourth argument optional indicates the step size The step increment is 1 if the fourth argument is not set The following is a simplified representation of the FOR command syntax diagram space number gt starting number a ending value ay If the ending value and or the step size is taken from the X register the Y register value changes or a variable change during execution of the FOR statement have no effect The value s at the start of the loop are used Examples FOR 1 1 10 For variable 1 1 to 10 FOR 1 1 10 2 For variable 1 1 to 10 step 2 FOR 8 YREG XREG For variable 8 YREG to XREG FOR 2 VAR 1 10 5 For variable 2 VAR 1 to 10 step 5 6 6 FOR variable X to Y step Z command syntax diagram The following example illustrates the use of the FOR command THIS PROGRAM WILL DELETE ANY PRO GRAM STORED IN MACRO LOCATION 7 70 2 1 ADDRESS OF SPECTRUM ANALYZER 80 Print z KILL 7 90 Print z STMAC 7 FO
240. s ZEROSP OFF PKCEN MCEN and CNTCF are not avail able in ZEROSP ZEROSP zero span mode query Response to ZEROSP query The response is the current zero span condition NOTE It may be preferable to use ZEROSP rather than SPAN 0 When ZEROSP is ON the front panel ZERO SPAN indicator is lit so you have a positive indication that the zero span mode is set in addition to the crt readout When ZEROSP is turned off the previous SPAN DIV setting is restored MXSPN max span mode command ON The instrument sweeps the entire frequency range in use FREQ no longer corresponds to center fre quency it now corresponds to the frequency at the tun able dot above the display or the marker on the display The previous FREQ SPAN DIV is saved and it is restored when MXSPN is OFF OFF MXSPN is cancelled leaving the FREQ SPAN DIV at the value previously selected Macro Memory Used 2 bytes Power up value Off Interaction Changing SPAN setting turns MXSPN OFF PKCEN MCEN and CNTCF are not available in MXSPN MXSPN max span mode query Response to MXSPN query The response is the current MXSPN condition NOTE It may be preferable to use MXSPN rather than SPAN MAX When MXSPN is ON the front panel MAX SPAN indicator is lit so you have a positive indication that the maximum span mode is set in addition to the crt readout When MXSPN is turned off the pre vious FREQUENCY SPAN DIV setting is re
241. s byte and encode the remaining seven bits to indicate the reason for asserting SRQ Status bytes are device dependent and are not specified in the IEEE 488 standard An addressed instrument will release its SRQ line when serial polled but other instruments may still hold it asserted When the controller has read the status byte of an addressed instrument it reasserts ATN and addresses the next instrument to talk then releases ATN and receives the instrument s status byte The routine continues until the controller no longer detects the SRQ line asserted At this time the controller should send the Serial Poll Disable SPD message and optionally send the UNT message to release the last active talker Performing A Parallel Poll The Parallel Poll PP function provides an instrument with the capability to present one and only one bit of status information to the controller without being previ ously addressed to talk The parallel polling capability requires a commitment by the system program to period ically conduct a parallel poll sequence When an instrument responds to a parallel poll the single data bit presented to the controller may or may not indicate a need for service If the data bit is used as a service request indication the controller should per form a serial poll in order to obtain a complete status byte with more information if the device has the SR function implemented Before an instrument can respond to a para
242. s not found the display data point is set to 500 0 If NUM is omitted from the com mand a default value of 0 is used A pattern recognition routine is used to recognize signals Macro Memory Used 2 bytes Interaction Display Data Point Commands Interaction There is no FIBIG query LFTNXT left next command aec 5 This command searches to the left of the current point to acquire the peak of a signal whose value is greater than NUM If a signal peak greater than NUM is not found the display data point is set to 0 0 If NUM is omitted from the command a default value of 0 is used A pattern recognition routine is used to recognize signals Macro Memory Used 2 bytes Interaction See Display Data Point Commands Interaction There is no LFTNXT query RGTNXT right next command 6 mum This command searches to the right of the current point to acquire the peak of a signal whose value is greater than NUM If a signal peak greater than NUM is not found the display data point is set to 1001 0 If NUM is omitted from the command a default value of O is used A pattern recognition routine is used to recognize signals Macro Memory Used 2 bytes Interaction See Display Data Point Commands Interaction There is no RGTNXT query FMAX find maximum value command 2 SP NuM NUM This routine sets the disp
243. s on how to set the GPIB address switches Some of the lines in the examples extend beyond the column width limitations When this happens the line is broken where a natural space occurs and the remainder of the line is indented on the immediately following line Because of this natural space a space must be added between the two example lines when joining them to form one program line SETTING AND QUERYING PROGRAMMABLE CONTROLS SETTING PROGRAMMABLE CONTROLS We can keep this simple because the spectrum analyzer lets you make complex spectrum measure ments semi automatically First we ll use the front panel pushbuttons then perform the same measurement under remote GPIB control using the 4041 controller Front Panel Operation Many measurements can be made with just three front panel settings lt blue SHIFT gt FREQ lt blue SHIFT gt SPAN DIV and blue SHIFT REF LEVEL The lt blue SHIFT gt FREQ setting changes the center frequency position of the spectrum window you are view ing tuning the spectrum analyzer to change the fre quency at the center of the crt The lt blue SHIFT gt SPAN DIV setting changes the size width of the window setting the frequency span of the crt horizontal axis The lt blue SHIFT gt REF LEVEL setting raises or lowers the window which sets the amplitude level of the top graticule line on the crt Here s how to operate the spectrum analyzer to measure the CAL OUT signal usin
244. s the line number on which the string will be printed The second argument sets the starting position for the string The third argument deter mines whether it is a number or a string that is to be printed Numbers can be printed in scientific notation SCI engineering notation ENG formatted FORMAT frequency format FFORMT or decimal DEC A brief description follows of the five ways a number can be returned The first or only link argument after the for mat specifier gives the total number of character posi tions occupied by the output Numbers are right justified and preceded by leading spaces If the number will not fit in the width specified a string of asterisks of the width specified will be output SCI prints a number in format The number is justified as described above and there are no trailing zeros ENG prints a number in the same manner as SCI except that the decimal point position is adjusted to make the exponent a power of 3 This corresponds to common enginnering units such as GHz and ms FORMAT prints a number in NR1 format A number to be printed with FORMAT cannot have a fractional part FFORMAT prints a number as a frequency in NR2 format with an identifier HZ KHZ MHZ or GHZ added There is no space between the number and the identifier The identifier is chosen so that the number to the left of the decimal point has a range of 1 999 The second link Macros 494AP Programmers ar
245. s the marking SYMBOLS In This Manual This symbol indicates where applicable tionary or other information is to be found As Marked on Equipment DANGER High voltage e Protective ground earth terminal ATTENTION refer to manual Refer to manual POWER Power Source This product is intended to operate from a power source that will not apply more than 250 V rms between the supply conductors or between either supply conduc tor and ground A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation Grounding the Product This product is grounded through the grounding con ductor of the power cord To avoid electrical shock plug the power cord into a properly wired receptable before connecting it to the power terminal A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation Danger From Loss of Ground Upon loss of the protective ground connection all accessible conductive parts including knobs and con trols that may appear to be insulating can render an electric shock Use the Proper Power Cord Use only the power cord and connector specified for your product Use only a power cord that is in good condition CSA certification applies to the spectrum analyzer with CSA certified power cords only the power cord shipped with your instrument and Tektronix Option A4 Intern
246. s triggered by an input signal A signal amplitude of at least 2 divisions is required and must occur after the hold off period that follows the previous sweep This sweep mode is often used to examine time domain signals in the zero span mode ZEROSP 4 24 LINE The power line input is selected as the trigger signal useful in both the frequency domain and time domain modes for signals with components related to the power line frequency EXT The sweep is triggered by a signal with an amplitude of at least 1 0 V peak connected to HORIZ TRIG EXT IN on the rear panel NUM 0 FRERUN 1 INT 2 LINE 3 EXT Macro Memory Used 2 bytes Power up value FRERUN Interaction The signal frequency required for inter nal trigger is related to the center frequency In the fre quency domain mode the required frequency corresponds to 1 2 division to the left of the left graticule edge in the time domain mode the required frequency is the center frequency In the frequency domain mode the required frequency must be within the selected frequency range TRIG triggering query Response to TRIG query EXT SIGSWP single sweep command On the first SIGSWP command the instrument enters the single sweep mode which stops the current sweep Once in the single sweep mode this command arms the sweep and lights the front panel READY light which remains lit for the duration of the sweep The spectrum an
247. ses si stai m ror 10 9 Spectrum Search 10 9 Measuring Signal Frequency With GOUN Feb Erie 10 9 Using COUNT GCGF rene 10 10 Ai ipa el DE 10 10 Higher Center Frequency Drift Rate Aftor Tuning 10 10 D 10 10 Using REPEAT for Signal Tracking Saarchss 10 10 Spectrum Search Using REPEAT 10 10 Messages on the Crt Using ibi g HM 10 11 Using CAL Over the Bus 10 11 Comparing FREQ and TUNE 10 11 Using the Time Measurement Feature 10 12 Using Multiband Sweep 10 12 Comparing the Status Byte and the ERR Responso e 10 13 Execution and Transfer Times 10 14 Appendix A Appendix B Page IEEE STD 488 GPIB SYSTEM CONCEPTS Mechanical Elements A 1 Electrical Elements A 1 Functional A 1 Typical GPIB System A 2 Talkers Listeners and Controllers A 2 Interface Control Messages A 2 Device Dependent Messages A 4 GPIB Signal Line Definitions A 6 Transfer Bus Handshake A 6 Management A 6 Interface Functions and Messages A 8 RL Remote Local Function A 8 T TE and L LE Talker and Listener FUNGON
248. signal print 1 1 harmonic test 140 Data print 3 1 fundamental frequency amplitude 150 Data enter mfreq stnum 3 print 4 1 xreg fformt 18 0 160 Data enter mampl stnum 2 print 4 28 xreg dec 6 1 170 Data print 5 1 180 Data print 6 1 harm level dbc step primar 190 Data for 1 1 10 200 Data enter 6 enter var 1 plus stnum 5 210 Data print var 5 2 var 1 dec 2 0 pstep sweep mfbig if signal 220 Data enter mampl print var 5 15 xreg dec 6 1 DBM 230 Data enter var 2 subt print var 5 33 xreg dec 6 1 240 Data else print var 5 6 no signal endi 250 Data next 260 Data text macro enter var 3 putreg freq else 270 Data dsline top 4 bottom print 4 2 NO SIGNAL FOUND 280 Data endi done emac 300 MACRO LOADING PROGRAM 310 On error 501 then gosub mdone When end of data goto mdone 320 Restore Point to 1st DATA item 330 Read d Read data 340 81 71 Start at 1st character position 350 E1 1en d Length of string 360 A1 pos d s1 Position of 5 370 If a1 0 then goto 420 No 5 send string 380 D1 seg d s1 a1 51 Segment out just one command 390 Gosub send str Send the one command 400 51 1 1 Set new starting position string 410 Goto 360 420 D1 seg d s1 e1 Segment out command 430 Gosub send str Send string 440 Goto 330 Go read the next data statement 450 Send str print 91 Print string 460 Print z d1 Send string
249. sition of the ordered points as absolute X values XN XZERO XINCR N PT OFF where XN is the value in XUNITS on the X axis XZERO is the center frequency except in the following cases XZERO 0 for time domain data ZEROSP Display Data and Crt Readout I O 494AP Programmers XINCR is the absolute point to point distance on the X axis XINCR span div 100 for FULL in frequency domain XINCR span div 50 for A or B in frequency domain XINCR TIME 100 for FULL in time domain XINCR TIME 50 for A or B in time domain is the point number 0 1 2 3 PT OFF is graticule center for frequency domain transfers and left graticule edge for time domain transfers PT OFF 250 for A or B in frequency domain PT OFF 500 for FULL in frequency domain PT OFF 0 in time domain For example point 100 could have the following absolute values XN 997 MHz for A or B with FREQ 1 GHz and SPAN 1 MHz XN 996 MHz for FULL with FREQ 1 GHz and SPAN 1 MHz XN 2 ms for FULL with SPAN 0 and TIME 2 ms Y Axis Scaling Y axis specifications YMULT YZERO and YOFF are used to interpret the data as the absolute value of the ordered data points YN YZERO YMULT VALN YOFF where YN is the value in YUNITS of point number N YZERO is the reference level in log vertical display mode and 0 in linear vertical display mode YMULT is the scale factor divided by 25 VALN is the unscaled integer data
250. space for responses than short messages Messages on the Crt Using RDOUT The spectrum analyzer accepts either a single set or a double set of quote marks to delimit the crt message With the 4041 controller use single quotes around the message inside the RDOUT command 100 Print z RDOUT SET THE PEAK AVERAGE CONTROL This is necessary because the 4041 uses a double set of quotes to set off the message following the colon in the Print statement A variation gets around this if you want quote marks to appear on the spectrum analyzer crt 100 Print Z RDOUT PRESS RETURN TO LOCAL Tw The controller strips off the first set in each double set of quote marks and transmits the second set of each double set for the display The RDOUT message continues to be displayed if the spectrum analyzer remains under remote control To demonstrate the above messages by themselves add the following statement 110 Goto 110 To scroll the RDOUT message to the top of the spec trum analyzer screen insert the following statement 105 Print z RDOUT Using CAL Over the Bus The CAL function activated from the front panel does two things It directs the operator in the adjustment of the four screwdriver adjustments AMPL and LOG CAL and Vertical and Horizontal POSITION CAL also per Helps and Hints 494AP Programmers forms an automatic calibration of the relative amplitude frequency and noise bandwidth of the resolution bandwid
251. st SSR and register valid RVALID 6 VIDEO ITAL DISPLAY ST ORAGE B FREQUENCY gt RESOLUTION SPANIDIV BANOWIDTH FREQ REF VIDEO RESOLUTION RANGE OSC FILTER BANDWIDTH TIME DIV 5559 12A Figure 4 7 Front panel General Purpose commands HELP help query The response is a list of all command headers in the GPIB language Response to HELP query with no argument Response to HELP query with FPANEL Each string represents one crt readout line of a help message All help messages black blue and green labeled functions and all marker menu functions are sent 4 33 Instrument Control 494AP Programmers by this command There is no HELP command STORE store settings command NUM The instrument control settings are stored into the selected memory location Range 0 to 9 Macro Memory Used 2 bytes Power up value The instrument STOREs its current settings in memory 0 automatically when the power is turned off overwriting any previously stored settings There is no STORE query RECALL recall settings command NUM The instrument control settings are recalled from the selected memory location Range 0 to 9 Macro Memory Used 2 bytes Power up value The instrument STOREs its current settings in memory 0 automatically when the power is turned off overwriting any previously stored settings Interaction If you try
252. stored Instrument Control 494AP Programmers RESBW resolution bandwidth command Pp C DEC NUM The nearest available resolution bandwidth is selected numbers between bandwidths that can be selected from the front panel are rounded Positive numbers above or below the range of bandwidth steps are rounded to the nearest step refer to Table 4 3 exe cution error message 32 is issued if the argument is beyond the normal range Table 4 3 RESOLUTION BANDWIDTH SELECTION Value Selects 3 17 Hz 31 6 Hz 10 Hz 31 7 Hz 316 Hz 100 Hz 317 Hz 3 16 kHz 1 kHz 3 17 kHz 31 6 kHz 10 kHz 31 7 kHz 316 kHz 31 7 kHz 316 kHz 317 kHz 1 72 MHz 1 73 MHz 5 49 MHz 100 kHz Non Option 07 300 kHz Option 07 Onl 1 MHz 3 MHz values outside the ranges listed cause execution error mes sage 32 to be issued AUTO Auto resolution is selected equivalent to ARES ON INC The next larger step is selected if possible DEC The next smaller step is selected if possi ble Macro Memory Used 5 bytes Examples RES 100 RESBW 1KHZ RES 1 5 MHZ RESBW INC 4 13 Instrument Control 494AP Programmers Range See Table 4 2 Power up value 3 MHz Interaction Any argument except AUTO cancels ARES ON Reducing resolution bandwidth may require a slower sweep speed TIME to maintain a calibrated display unless TIME DIV is set to AUTO RESBW resolution bandwidth query Response to RE
253. t status byte with bit seven asserted When the instrument requesting service is found program control is transferred to a service routine for that instrument When the service routine is completed program control returns to the main program The controller does not have to see the SRQ line asserted to perform a polling routine it may do so whenever a program requires it REN Remote Enable The system controller asserts the REN signal line whenever the interface system operates under remote program control Used with other interface control messages such as LLO Local Lockout or GTL Go To Local the REN signal causes an instru ment on the bus to select between two alternate sources of programming data A remote local interface function indicates to an instrument that the instrument will use either information input from the interface remote or to information input by the operator via the front panel con trols local End Or Identify A talker can use the EOI signal line to indicate the end of a data transfer sequence The talker asserts EO as the last byte of data is transmitted In this case the EOI line is essentially a ninth data bit and must observe the same settling time as the data on the data bus When an instrument controller is listening it assumes that a data byte sent with EOI asserted is the last data byte in the complete message When the instru ment controller is talking it may assert the EOI signal li
254. t Delimiter 2 2 Message Terminator TERM 2 2 Format 2 2 Input Buffering and Execution 2 2 Command Format eee eee eror ono 2 2 HORGOT SUMMO M 2 2 Header Delimiter SP 2 3 Argument Delimiter 2 3 Argument 2 3 Aj nion MM 2 3 fj 2 3 Character 2 4 Link 2 4 String 2 4 Section 2 Section 3 Section 4 Page continued End Bo 2 4 Binary o 2 4 Query 2 4 Query Response Format 2 4 Spectrum Analyzer Output Messages 2 5 Output Message 2 5 Output Message Execution 2 5 Spectrum Analyzer Compatibility 2 5 hl iaa dior 2 5 DEGAUS 2 5 IDENT Command 2 5 Readout Maximum 2 5 Service 15 2 5 Affect of Busy on Device Dependent sss 2 5 GET Group Execute Trigger 2 6 Reference _ 2 6 RDOUT Command
255. te The handshake sequence is performed via the NRFD DAV and NDAC signal lines on the bus see Figure A 5 Both functions must respond to ATN within 200 n The SH function must wait for the RFD Ready For Data message plus wait at least 2 us before asserting DAV this allows the data to settle on the data bus If three state drivers are used the settling time is reduced to RFD plus 1 1 us Faster settling times are allowed under special conditions and warning notes in the stan dard The time it takes for the AH function to accept an interface message byte is dependent on how the designer implemented the function DC Device Clear Function The DCL Device Clear function allows the controller in charge to clear any or all instruments on the bus The controller under program direction asserts ATN and sends either the universal DCL Device Clear command or the SDC Selected Device Clear command When the DCL message is received all instruments on the bus must clear or initialize their internal device functions When the controller sends the SDC command only those instruments that have been previously addressed to listen must respond The IEEE 488 stan dard does not specify the settings an instrument must go to as a result of receiving the DCL or SDC command In general these commands are used only to clear the GPIB interface circuits within an instrument DT Device Trigger Function The DT Device Trigger function all
256. tem failed 78 IF count failed 79 Power supply out of regulation 80 Frequency reference unlocked 82 1st LO tuning system recovered from a failure this error message is issued the macro in progress will be aborted 140 141 143 150 151 152 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 ERR RESPONSES In Numerical Order Quick Reference Meaning 2nd LO tuning system recovered from a failure Phase lock system recovered from a failure IF count recovered from a failure Power supply regained regulation Frequency reference re locked Unrecognized event occurred Power just came on Operation complete end of sweep SRQ was requested Function not available when SGTRAK is on Frequency range limited in 75 Q input Option 07 only Frequency out of range after step Bandwidth mode is not available when in linear Illegal sweep range Argument out of range MKTIME not available unless in zero span mode MKTIME out of range ROFSET out of range STEP size out of range set to maximum SPAN defaulted to minimum span Frequency out of range because marker is on inactive trace Function not available when marker is on an inactive trace Function not available when marker is off Function not available when delta marker is off Function not available in BWMODE Function not available when marker is on a B SAVEA trace Function not available when in dB Hz Si
257. th filters The CAL command allows these func tions to be separated so that either the adjustments or the automatic calibration will be done To recreate the front panel calibration function over the bus requires that five commands be sent to the instrument four for the adjustments and one for the automatic calibration User prompt messages are displayed on the crt screen Since the spectrum analyzer is in the Remote mode the controller keyboard must be used to go to the next adjustment step A device clear is sent to the spectrum analyzer to terminate the execution of each adjustment command Note that HPOS could be deleted without affecting the other adjustments but the others should be done in the recommended order 80 2 1 ADDRESS OF SPECTRUM ANALYZER 100 Print z RDO CONNECT CAL OUT TO RF INPUT 110 Print z RDO HIT RETURN AFTER COMPLETING EACH STEP 120 Input b 130 Print z CAL AMPL 140 Input b 150 WBYTE DCL 160 Print z CAL HPOS 170 Input b 180 WBYTE DCL 190 Print z CAL VPOS 200 Input b 210 WBYTE DCL 220 Print z CAL LOG 230 Input b 240 WBYTE DCL 250 Print z CAL AUTO 260 End COMPARING FREQ AND TUNE The FREQ command argument is in absolute fre quency while the TUNE command argument is in relative frequency Use FREQ to change the center frequency to some value you supply as a command argument Use TUNE to change the center frequency by some offset you supply as a command argument
258. the 4041 BASIC examples in this manual the variable Z has been used to represent the spectrum analyzer GPIB address A constant in the range of 1 to 30 matching the spec trum analyzer address can be assigned to the variable rA 80 2 1 ADDRESS OF SPECTRUM ANALYZER EQUALS 1 100 Print z FREQ 100 MHZ 110 Print z SPAN 1 MHZ 120 Print z REFLVL 20 DBM or 80 Z 1 100 Print z FREQ 100 MHZ SPAN 1 MHZ REFLVL 20 DBM As this last statement shows all three commands can be strung together delimited by semicolons When the spectrum analyzer executes these com mands it tunes the CAL OUT signal to center screen changes to the narrower span and changes the refer ence level to display the signal peak at the top of the screen Resolution bandwidth time division input attenuation and IF gain are changed automatically as necessary Because the spectrum analyzer is calibrated for this display as part of the turn on procedure the sig nal peak should occur vertically at the reference level and horizontally at the graticule center If not refer to the Initial Turn On procedure in the Operators Manual or Operators Handbook or better yet try the automatic calibration routine described in lt blue SHIFT gt CAL under Display Parameters in Section 4 of the Operators Manual If you receive an SRQ message on the screen of the spectrum analyzer add an SRQ handler to the program This sequence can be added to any BASIC progr
259. the EOS condition Macro Memory Used 2 bytes Power up value Off EOS end of sweep query System Commands and Queries 494AP Programmers Response to EOS query CD Gaa Cor RQS request service command ON SRQ is asserted when abnormal status condi tions occur OFF SRQ is not asserted is masked when abnor mal status occurs Macro Memory Used 2 bytes Power up value On Interaction RQS is always OFF in the talk only and listen only modes RQS request service query Response to RQS query amyn ue Ras sP _ WARMSG warning message command ON All warning messages will be issued see Table 9 2 OFF No warning messages will be issued see Table 9 2 Table 9 2 WARNING MESSAGES Description Execution Warnings FREQ change caused EXMXR change 50 SPAN defaulted to MAX 52 UNCAL light turned on 53 Multiple use of display buffer 54 UNCAL light turned off STEP size out of range set to maximum SPAN defaulted to minimum span Macro Memory Used 2 bytes Power up value On WARMSG warning message query Response to WARMSG query System Commands and Queries 494AP Programmers STATUS BYTE N o e P STATUS BYTE response to serial poll When the controller addresses the spectrum analyzer as a talker and sends the SPE Serial Poll Enable com mand the
260. the GPIB address refer to Table 1 1 The instrument s primary address 0 through 31 is the value of the lower five bits which are labeled 4 through 8 in Figure 1 3 These switches are read each time power is turned on to the instrument and again each time the RESET TO LOCAL or lt blue SHIFT gt PLOT pushbutton is pressed The address transmitted by the controller is seven bits wide The first five bits are the primary address and the last two bits determine whether it is a listen address 32 primary address or talk address 64 primary address For example 0100010 is primary address 2 a listener and 1000010 is primary address 2 a talker Secondary addresses when both bits 6 and 7 are set are not used by the spectrum analyzer so are ignored GPIB ADDRESS LF OR EOI TALK ONLY LISTEN ONLY Figure 1 3 Rear panel GPIB ADDRESS switches The LF OR EOI switch message terminator and the TALK ONLY and LISTEN ONLY switches are part of the same switch bank Set the switches as desired but do not use address 0 with Tektronix 4050 Series controllers they reserve this address for themselves Selecting a primary address of 31 logically removes the spectrum analyzer from the bus it does not respond to any GPIB address but remains both unlistened and untalked Remember if you change these switches when the instrument is running you must press RESET TO LOCAL lt blue SHIFT gt PLOT to cause the primary address to be updated
261. the NSELVL por tion of the SET response NOTE If the Primary marker is out of the range of digital storage one of the following will be returned e 200 0 if under range e 4200 0 if over range 999 9 if markers are off SGTRAK signal track command SGTRAK attempts to keep the signal at center screen as long as the signal does not drift off screen between sweeps Marker execution error message 120 is issued if the marker is on an inactive trace If there is no signal at the marker location or the signal disappears SGTRAK goes to IDLE The signal track function takes effect at the end of the sweep after the SGTRAK command is given SGTRAK is on during IDLE but it is not tracking because there is no signal at the marker location ON or IDLE The signal track is turned on OFF The signal track is turned off Macro Memory Used 2 bytes Power up value OFF Marker System 494AP Programmers Interaction MARKER is OFF SGTRAK sets MARKER to SINGLE Neither IDENT nor BWMODE are available while SGTRAK is ON execution error message 101 will be issued if either is used The definition of the criteria for a signal is set by the THRHLD command SGTRAK signal track query Response to SGTRAK query 7 MARKER POSITIONING The marker positioning commands and queries move the display pointer to the Primary marker position DPMK return the amplitude of the Primary or Secon da
262. the spec trum analyzer firmware may be needed to reduce the drift rate Noise Noise can be overcome in several ways To reduce noise peaks smooth the data by averaging in digital storage Averaging is enabled by the CRSOR command use CRSOR AVG or CRSOR KNOB and set the cursor 10 10 above the noise by turning the front panel knob Further smoothing is possible by slowing the sweep TIME com mand so that the amount of data averaged for each point in digital storage is increased Noise peaks can also be reduced smoothed by the video filters There is an alternative to smoothing the data The signal search commands can include a parameter that sets a threshold for the signal search routine If this parameter is set above the noise but below any desired signal the routine ignores the noise and finds the signal But how do you find this level that is not too high and not too low There is no one level that will work in every case A level may be estimated by using FMIN to locate the negative noise peaks and adding a constant to approximate the positive noise peaks Adjust the con stant if resolution bandwidth is changed Another method is to force signals off screen with the FREQ command and use FMAX to acquire the most positive noise peak In practice a combination of these methods may be applied to handle varying conditions For example smooth the data with the narrow video filter and average it as it is acquired to enabl
263. the spec trum analyzer terminates the output according to the set ting of the EOI OR LF switch SPECTRUM ANALYZER COMPATIBILITY Most of the primary modes of the controls and func tions of the Tektronix 49XP Series portable spectrum analyzers and 275XP Series laboratory benchtop spec trum analyzers are identical For purposes of feature comparison here is some useful information the 492AP is comparable to the 2754 and the 2755 the 495P is comparable to the 2753 and the 494AP is comparable to the 2756 Following are some of the areas where operations or results will differ GPIB 494P 492AP 495P 495P Option 05 494AP The DCL interface message is handled by interrupts and will stop execution of the command in progress 492P 496P The processor is required to not be busy e g executing a WAIT message in order for DCL to be handshook in DEGAUS Command 494P 492AP 494AP DEGAUS may be executed in any span 492P DEGAUS may be executed in spans 1 MHz div or less IDENT Command 494P 492AP 494AP The span must be 50 kHz div for coaxial bands 0 21 GHz or 50 MHz div for waveguide bands 492P The span must be at 500 kHz div 495P 495P Option 05 The span must be 50 kHz div Readout Maximum 494P 492AP 495P 495P Option 05 494AP Readout strings can contain up to 40 characters 492P 496P Readout strings can contain up to 32 characters Service Requests 494
264. the starting character position for the input number With FREQ the GHz MHz KHz and Hz terminators are valid and the corresponding front panel pushbuttons will light GHz will multiply the input number by 1 000 000 000 MHz will multiply the input number by 1 000 000 KHz will multiply the input number by 1 000 and Hz will not change the input number With SIGNED the dBX and dBX terminators are valid and the corresponding front panel pushbuttons will light dBX will not change the input number but dBX will make the input number negative With UNSIGN the dB terminator is valid and the front panel dB pushbutton will light If DSTERM display terminators is used the words END WITH and the valid terminators will be displayed two lines below the entry line with an underline on the following line If an undefined key is pressed the macro will be aborted If a terminator is pressed without a number or a SHIFT pushbutton is pressed XREG stays the same You can load a default value in XREG with the ENTER command before INPNUM then just press the termina tor pushbutton to get that value default NOTE The message PRESS SHIFT TO ABORT is always displayed on line 16 so that line is not available for input The following example illustrates the use of the INP NUM command The example is illustrated in Figure 6 1 80 2 1 ADDRESS OF SPECTRUM ANALYZER 100 Print z CLEAR 110 Printz TEXT 120 PrintZz PRINT
265. to within 200 ns They must also respond to IFC in less than 100 us An instrument may be a talker only a listener only or implement all functions In any case its address code has the form X10TTTTT for a talker and XO1LLLLL for a listener For instruments with both T and L functions the T bit binary values are usually equal to the binary value of the L bits Before applying power to the system the system operator sets these five least significant bits by means of an address switch on each instrument The controllers address code may be implemented in software The system program run from the controller desig nates the primary talker and primary listener status of the desired instruments by coding data bits 6 and 7 1 0 respectively for a talker and 0 1 respectively for a listener Secondary talk and listen addresses or com mands are represented by the controller sending both data bits 6 and 7 as a logical 1 The controller may listen to bus traffic without actually addressing itself over the bus SH and AH Source and Acceptor Handshake Functions NOTE Although discussed under one heading the SH and AH functions are independent of each other The SH Source Handshake function guarantees proper transmission of data while the AH Acceptor Handshake function guarantees proper reception of data The interlocked handshake sequence between these two functions guarantees asynchronous transfer of each data by
266. to be either time related lines or spectral lines belonging to the same pulse This extends to multi ple lines in a group of such lines the highest amplitude line will be identified as the center of the signal Figures 5 3 through 5 7 illustrate the use of STYPE All of the figures use the signal finding command of MRGTNX Any of the other signal finding commands MLFTNX MFBIG HRAMPL and LRAMPL work simi larly according to their specific function Marker System 494AP Programmers Figures 5 3 5 4 and 5 5 If CW was selected the spectrum analyzer would not identify any signal because none of the signals displayed meets the minimum bandwidth criteria If PULSE was selected the signals labeled D E and F would be identified because the other signals in the display are less than 2 minor divisions apart If the signals were greater than 2 minor divisions apart PULSE would have identified all labeled signals A B C etc If SPURS was selected all signals would be identified A B C etc Figure 5 6 The MRGTNX selection begins at the left screen margin With this display CW PULSE and SPURS will each identify all of the signals because they all meet the minimum bandwidth criteria i e the selec tions would be A B C D and E Figure 5 7 In Figure 5 7 the threshold is assumed to be 70 dBm If CW was selected signals B E F and G would be identified The other signals would not be identified becaus
267. to recall settings from an empty memory location execution error message 62 is issued There is no RECALL query RDATA register data command F PSET BINARY BLOCK This command transfers directly to a numbered storage register either a front panel setting or a waveform and associated data The data is transferred in a coded binary format It is intended that this information be obtained from a previous RDATA query 4 34 FPSET The front panel settings contained in the binary block are transferred to the indicated register DISP The waveform and the associeted readout and scaling data contained in the binary block are transferred to the associated register NUM The number of the storage register to which data will be transferred If the number is outside of the range of 0 9 when FPSET is used or the range 0 8 when DISP is used execution error message 47 will be issued The binary data sent is internally checksummed This checksum is different than the checksum added in the binary block format If the internal checksum does not match the data execution error 190 will be issued RDATA register data query Coa The RDATA query transfers directly from a num bered storage register either a front panel setting or a waveform and associated data The data is transferred in a coded binary format It is intended that this information be used only as data for a subsequent RDATA com mand
268. track the Pri mary marker Macro Memory Used 2 bytes Power up value OFF Interaction The WFID portion of any previous WFMPRE command or the CRVID portion of any previ ous CURVE command is cancelled and the FULL waveform for data transfers and waveform processing is selected WFID or CRVID other than FULL sets MCPOIN to OFF If MARKER is OFF MCPOIN sets MARKER to SINGLE MCPOIN marker coupled to the display pointer query Response to MCPOIN query MEXCHG marker exchange command The Primary marker moves to the former location of the Secondary marker and the Secondary marker moves to the former location of the Primary marker If the Secondary marker is off the screen before the marker exchange the instrument center frequency will be set to the old Secondary marker frequency and the old Primary marker i e the new Secondary marker will be off the screen Macro Memory Used 1 byte Interaction MEXCHG sets MARKER to DELTA There is no MEXCHG query MFREQ marker frequency command The MFREQ command sets the frequency of the Pri mary marker to the value given by NUM Macro Memory Used 6 bytes Examples MFREQ 100000 MFR 1 8 GHZ MFREQ PRIMAR 200 KHZ MFR PRI 200MHZ Range Active trace is 0 Hz to 325 GHz Inacative trace is limited to the edge of the screen Marker System 494AP Programmers Power up value Markers are off when power is first turned on to the instru
269. transfers the data to digital storage while executing and the display data point com mands act on the data while executing The CURVE query by contrast does not transfer the data until after the entire message is executed and the spectrum analyzer receives its talk address Thus if these mes sage units are mixed in a message the contents of the buffer may be changed between when it is loaded and when it is acted on or transferred 80 Z 1 ADDRESS OF SPECTRUM ANALYZER 100 Waveform processing and I O 110 Dim b 1000 120 Print 4z CURVE 130 Input z b 140 Print z CURVE A 150 End Line 120 Requests a curve which the spectrum analyzer buffers Line 130 Inputs the curve before it is overwritten by line 140 The semicolons enclosing A at the end of line 140 instruct the controller to squeeze out unneeded spaces between the numbers as the PRINT statement transmits array A Without a semicolon immediately after the array variable this line does not run properly With this semicolon the controller places a space between numbers the spectrum analyzer accepts the space or other format characters as well as a comma for a del imiter FINDING SIGNALS WITH WAVEFORM PROCESSING The waveform processing functions in the spectrum analyzer allow many waveform parameters to be found without transferring a waveform to the controller You will get better results if you understand how the routines work and what their l
270. troler in a GPIB system These commands and queries are described in this section in three groups related to instrument parameters message execution and status and error reporting NUM Argument Unless otherwise stated the values for the NUM argument are 1 ON e gt 0 5 are rounded to 1 e 0 OFF e lt 0 5 are rounded to 0 Use in Macros Most of the system commands in this section can be incorporated into macros designed to your specific needs No queries can be used within macros Since there is a total of 8k bytes of memory dedicated for macro use it is important that you know the number of bytes used for each command and keep this in mind while preparing macros This maximum number of bytes used is included with the commands in this section and there is also a table in the foldout pages at the back of this manual that lists all available spectrum analyzer commands and the bytes used by each INSTRUMENT PARAMETERS The commands and queries in this group return instrument settings SET return the instrument identification parameters ID initialize settings INIT and control return of the query response header SET instrument settings query SET The instrument returns a string of commands that can be learned for later transfer to the spectrum analyzer when the same setup is desired The response includes only those functions necessary for such a setup To assure no interaction that might
271. turns the amount of memory that macro number NUM is using Response to MEMORY query 0 7 18 If number argument that is out of range 1 30 is sent execution error message 106 is issued and O is returned If a macro is not stored at the NUM location macro execution error 165 is issued and O is returned There is no MEMORY command STNUM store number command 6 nuw The STNUM command stores the XREG value in the variable NUM If NUM is less than 1 NUM is set to 1 If NUM is out of range macro execution error message 176 is issued Examples STNUM 1 Copies the number in XREG to variable number 1 STNUM 9 Copies the number in XREG to variable number 9 Macro Memory Used 2 bytes Range NUM is 1 to 30 There is no STNUM query 6 15 Macros 494AP Programmers MENU macro menu command CD 18 REY RLUNIT STORE The MENU command will display the requested menu A new value for that setting can then be input from the front panel After the entry is complete the macro will continue If either the blue or green SHIFT pushbutton is pressed macro execution will resume with no value change If an invalid pushbutton is pressed the macro is aborted at this point and cannot be restarted For a description of the command arguments see the description of the command whose mnemonic is the same as the argument Macro Memory Used
272. ues 10 1 Signal Processing 10 1 Running Programs Without a Controller 10 1 Date AcQuIBIDOIL siis onerat Yao ni 10 2 Synchronizing Controller and Spectrum 10 2 Synchronizing with the Sweep 10 2 Using the End of Sweep SRQ 10 2 INPUT An Alternative 10 4 Binary Waveform Transfer 10 4 Getting Spectrum Analyzer Binary Curva QUE 10 4 Sending a Binary CURVE to the Spectrum Analyzer 10 5 Getting and Sending Binary Data with RDATA and RDATA 10 5 Scaling Saving and Graphing Waveform Data 10 5 Saving the Scaled Array 10 6 Storing Settings cresccccsseassevesossessisszee 10 6 494AP Programmers Section 10 vi Page continued USING PLOT 10 6 Using PLOT With Macros 10 6 Multiple Use of Display Buffer 10 7 Buffer Data 10 7 Order Dependent Conflicts 10 8 Finding Signals with Waveform POCNE EIN 10 8 Understanding How Waveform Processing Works 10 8 Setting the Threshold 10 9 Acquiring Data for Waveform Processing coe eivacse
273. uffers the last byte hex FF but does not put it into digital storage Getting and Sending Binary Data with RDATA and RDATA The following routine illustrates the transfer of set tings directly to and from the battery backed up memory A similar program may be used with displays The rou tine reads the settings from memory 1 and sends them to memory 2 THIS PROGRAM WILL OVERWRITE ANY SETTINGS STORED IN MEMORY LOCA TIONS 1 OR 2 100 Z 1 ADDRESS OF SPECTRUM ANALYZER 110 Integer w 130 120 Print z STORE 1 130 Input prompt RDATA FPSET 1 using FA FA 8 dels 2 h1 h2 w 140 Print 2 RDATA FPSET 2 150 Print using 8 z w Line 110 Dimensions an integer array to hold the settings data This must be an integer array Line 120 Places present instrument settings in memory 1 to insure there is something to transfer Line 130 Read the settings from the instrument The delimiter is set to a colon with the dels clause Since there is a link argument in the returned header before the binary data the header will be input as two strings h1 and h2 as specified by FA FA in the using clause The image specifier for the array 8 selects binary block format and places each 8 bit byte in one Helps and Hints 494AP Programmers location in array w The byte count and checksum are input and checked automatically A checksum error results in a trappable interrupt to the 4041 Line 140
274. ular instrument s purpose need be implemented A TYPICAL GPIB SYSTEM typical GPIB instrumentation system is illustrated in Figure A 2 and it includes the nomenclature for the six teen active signal lines Only four instruments are shown connected directly to the control bus but the GPIB can support up to fifteen instruments connected directly to the bus However more than fifteen devices can be inter faced to a single bus if they do not connect directly to the bus but are interfaced through a primary device Such a scheme can be used for programmable plug ins housed in a mainframe where the mainframe is addressed with a primary address code and the plug ins are addressed with a secondary address code To maintain the electrical characteristics of the bus a device load should be connected for each two meters of cable length Although instruments are usually spaced no more than two meters apart they can be separated farther apart if the required number of device loads are lumped at any given point For proper operation at least two thirds of the instruments connected directly to the bus must be in the power on state A 2 TALKERS LISTENERS AND CONTROLLERS A talker is an instrument that can send messages and data over the bus a listener is an instrument that can accept messages and data from the bus An instru ment can be a talker only listener only or be both a talker and a listener Unless a device is in the talk only
275. used the DATA pointer is set to LABEL NUM Examples MRESTO When a READ command is used the macro will start looking for the first MDATA command in the macro MRESTO 1 When a READ command is used the macro will start looking for the first MDATA command after LABEL 1 The following example illustrates the use of the MDATA READ and MRESTO commands THIS PROGRAM WILL DELETE ANY PRO GRAM STORED IN MACRO LOCATION 7 70 Z 1 ADDRESS OF SPECTRUM ANALYZER 80 Print z KILL 7 90 Print z STMAC 7 MRESTO TEST 100 Print z MDATA 1GHz 110 Print z LABEL 1 120 Print z MDATA 2GHZ 130 Print z MDATA 3GHZ 140 Print z MDATA 4GHZ 150 Print z MRESTO 160 Print z GOSUB 2 170 Print z GOSUB 2 180 Print z GOSUB 2 190 Print z MRESTO 1 200 Print z GOSUB 2 210 Print z GOSUB 2 220 Print z GOSUB 2 230 Print z DONE 240 Print z LABEL 2 250 Print z READ 260 Print z PUTREG FREQ Macros 494AP Programmers 270 Print z SWEEP MFBIG PAUSE 5 280 Print z RETURN 290 Print z EMAC Line 100 Stores the value of 1 GHz Line 110 Sets label marker 1 at this position Line 120 Stores the value of 2 GHz Line 130 Stores the value of 3 GHz Line 140 Stores the value of 4 GHz Line 150 Sets the DATA pointer to the first MDATA value 1GHZ Line 160 GOSUBs to LABEL 2 which reads 1GHZ into XREG then sets the center frequency to 1 GHz Line 170 GOSUBs to LABE
276. ventions and Features This standard promotes ease of operation and makes this spectrum analyzer compatible with other Tek tronix instruments and as much as possible with GPIB instruments from other manufacturers GPIB PUSHBUTTON AND INDICATORS see Figure 1 1 RESET TO LOCAL REMOTE The REMOTE indicator is lit when the spectrum analyzer is under control of the GPIB controller While under remote control most other front panel controls and pushbuttons are not active indicators will still reflect the current state of all front panel functions except TIME DIV MIN RF ATTEN dB and PEAK AVERAGE ADDRESSED INDICATOR REF LEVEL CENTER FREQUENCY MER LEVEL MARKER FREQUENCY M E FETTET MESTAAN REQ AREF VIDEO RESOLUTION AANGE OSC SANOWIOTH ILE E I RESET TO LOCAL REMOTE INDICATOR FREQUENCY RESOLUTION SPAN DIV BANDWIDTH 5559 07 Figure 1 1 GPIB pushbutton and indicators 1 1 Introduction to GPIB Operation 494AP Programmers The REMOTE indicator is not lit when the instrument is under local operator control While under local con trol the instrument does not execute GPIB messages that would conflict with front panel controls and it does not accept the CURVE input command When the instrument is under remote control and RESET TO LOCAL is pressed local control is restored to the operator unless the controller prevents this with the local lockout message Programmable functions
277. which immediately resets the talk or listen function if active Addresses that do not match those set by the rear panel switches are handshaked and discarded by the interface When the current talk or listen address MTA or MLA is decoded by the interface it holds up the handshake until the spectrum analyzer can get involved The instrument will get involved as soon as it can service the interrupt The front panel ADDRESSED light and the crt readout will be modified as soon as the programs are completed that update the addressed status Because the spectrum analyzer gets involved when a current address is received addressed commands are affected by the speed at which the service interrupts can be handled Serial poll is similarly affected if MTA pre ceded SPE 3 GTL is handshaked immediately by the interface If the spectrum analyzer is already listen addressed the spectrum analyzer returns to local control executes GTL after executing any message in its buffer except WAIT or message units following WAIT REN unasserted is handled in the same manner as the GTL command 4 DCL requires spectrum analyzer action that will hold up the handshake if the spectrum analyzer is busy If the spectrum analyzer is listen addressed SDC is treated in the same manner These two device clear messages are executed as soon as they are received 9 GET also requires spectrum analyzer action so its handshake occurs only when the interrupt can be ha
278. with the MLOCAT header There is no MLOCAT command MTOP marker to reference level command MTOP Marker System 494AP Programmers The MTOP command changes REFLVL to move the marker to the reference level or as close as possible given the specified vertical display and reference level accuracies Macro Memory Used 1 byte Interaction Marker execution error message 121 is issued if the Primary marker is on an inactive trace If MARKER is OFF MTOP sets MARKER to SINGLE MTOP is not available in BWMODE There is no MTOP query MTUNE tune marker command The Primary marker frequency is changed by the value of the number argument Marker execution error message 120 is issued if the marker is not on an active trace and the resulting marker frequency would not be on the screen MTUNE moves the Primary marker to center screen and changes center frequency if the Primary marker is on an active trace and the frequency is not on the screen Macro Memory Used 6 bytes Examples MTUNE 100 MTU 200 MHZ Range The same as TUNE refer to Table 4 2 Interaction If MARKER is OFF MTUNE sets MARKER to SINGLE There is no MTUNE query MARKER FINDING The marker finding commands move the Primary marker to the next higher or lower amplitude signal HRAMPL or LRAMPL set the bandwidth number BWNUM place delta markers at a given amplitude BWMODE move the Primary marker to the largest on scr
279. x2 x2 y3 y2 y1 140 Goto 150 150 Dim m n 2 160 Integer w n 170 Gosub wave in 180 Fori 1ton 190 m i 1 x1 x2 i 1 x3 200 m i 2 y1 y2 w i y3 210 Next i 220 Stop 230 Wave in print z WFM ENC BIN 240 Input prompt using FA 8 dels z head w 250 Return Line 110 Clears the waveform arrays 10 5 Helps and Hints 494AP Programmers Line 120 Requests the waveform preamble and a binary curve Line 130 Inputs the spectrum analyzer WFMPRE response storing the first seven numbers it finds as vari ables n x3 x2 etc Lines 150 160 and 170 Calls subroutine wave in to put the waveform in w Lines 180 220 Scales the waveform integers and fills array m with the result The first number in each ele ment of the array is a frequency and the second number is the power detected at that frequency The elements can be printed on the screen with the statement PRINT m or any element i can be printed with the statement PRINT m i Lines 230 and 240 Uses the input prompt to request a curve The field input for the header string is delimited from the data by a comma with the dels clause and enters the array w in an 8 bit word format with the image specifier 8 The byte count words and checksum are input and checked automatically Checksum failure results in a trapable error interrupt to the 4041 Saving the Scaled Array When you transfer an array to tape first f
280. y take a long time to complete the spectrum analyzer is busy only for the time it takes to load the output buffer Effect of Busy on Interface Messages Interface messages and the rtl message from the RESET TO LOCAL button are processed despite busy status If RESET TO LOCAL interrupts a message the spectrum analyzer tries to finish the rest of the message after local control is restored At that time commands that try to change a front panel setting will result in error SRQs because they conflict with local control 9 9 System Commands and Queries 494AP Programmers The response of the spectrum analyzer to interface messages depends on how they are handled Some interface messages are handled by the GPIB interface while others require action by the spectrum analyzer The latter generally involve the spectrum analyzer GPIB address and are part of the firmware rather than on the interface The speed with which these commands can be handshaked depends on how fast the interrupt can be serviced which in most cases should be within a few hundred ys The following apply to interface messages received by the spectrum analyzer 1 Universal commands LLO SPE and SPD are handshaked and acted on by the interface so they are unaffected by spectrum analyzer activity The serial poll proceeds without delay if the talk address follows since this function is handled by the interface 2 UNL and UNT are handshaked by the interface
281. you are informed in this manual of possible interaction involving waveform processing and waveform data 1 0 executed the same spectrum analyzer message This occurs in Section 7 under the Interaction part of the CURVE command and under Display Data Point Commands Interaction in Section 8 There is no conflict in many cases because the spec trum analyzer buffers the message you send and then executes it in the order you sent it For example you can use the spectrum analyzer as a waveform processor for spectrum data you previously acquired in array A by entering the following program This example cannot be used in customized macros as presented here because it contains the CURVE com mand 80 2 1 ADDRESS OF SPECTRUM ANALYZER 100 BUFFER DEMO 110 Print z SIGSWP 120 Print z CURVE a FIBIG POINT 130 Input z B1 B2 DISPLAY DATA WAVEFORM BUFFER DIGITAL STORAGE CURVE CRVID WFMPRE WFID Helps and Hints 494AP Programmers In this case the spectrum analyzer does what you ask it loads a waveform into digital storage and returns the point at the peak of the largest signal SIGSWP is included to keep the spectrum analyzer from overwriting the CURVE commmand Interaction is possible in other cases however because there is only one display data buffer used for both display input and output and as workspace for waveform processing For instance conflicts can arise if the CURVE command or the

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