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FRACTIONAL N SIMPLIFIES FREQUENCY SYNTHESIS

1. Table 1 il lustrates this point quite well Note that after ten reference periods the VCO has gone one full cycle be yond what would be needed to close integral multiple of the reference fre quency 100 kHz in this example and the system can be phase locked Be tween removals of one cycle however the instantaneous frequency is still 1 01 MHz The element required to achieve this mode of operation is a pulse remover and is shown in Figure 5 The output of the phase detector is a sawtooth riding on a dc voltage The output of the phase detector increases linearity as the phase of the VCO divided by N ad vances on the reference signal Each Table 1 Phase Relationship of the Integral Part of the VCO Frequency Times N Relative to its Fractional Part as Expressed in Phase Advancement No of Ref Periods 100 kHz N x Fref 1 MHz ref Integer of the VCO frequency No of Completed Cycles of N F 1 01 MHz 0 1 cycle of phase 0 2 cycle of phase 0 3 cycle of phase 0 4 cycle of phase 0 9 cycle of phase 1 full cycle of phase 360 Nx N F Integer and fractional part of the VCO frequency the loop and phase lock this system If one VCO cycle could somehow be re moved from the string of VCO cycles after the passage of ten reference periods the average phase advance ment would be cancelled That is the output of the phase detector instead of increasing without bound as shown in Figure 3 wou
2. the like of which he may never have before experienced Blinding flashes of lightning will cross the repair shop and mighty thunder claps will be heard the instrument the user and his toolbox will crumble and vanish into dust to be swept away by the night janitor 5345 S NEED AIR TOO When the air filters in the 5345 go unchanged for a long period of time dirt build up eventually clogs air flow resulting in abnormal heat rise inside the unit This increased temperature of course adversely affects the 5345 s reliability Also once the filters are clogged the fan begins drawing air through the front panel switches Dust eventually collects around the switch contacts and impairs their proper operation After a careful review of the situation WWW HPARCHIVE COM the factory has approved removal of the air filters altogether Experiments show that in a normal operating envi ronment dust build up will only be slightly higher This is more than off set by the reduction in ambient tem perature Of course instruments that operate in particularly dusty environ ments should retain their filters and they should be regularly maintained If new filters are needed they can be ordered by specifying HP part number 3150 0241 for the bottom filter and 3150 0242 for the side filter a SERVICE NOTES SERVICE NOTE ORDER FORM INSTRUCTIONS 1 If you want service notes please check the appropri
3. 07652 Fran Groat 5301 Stevens Creek Bivd Santa Clara CA 95050 O 5062 Oct 10 14 450 Student Name Company Name e City State Zip To enroll in any of the seminars fill out the registration form and mail it with your check to the address shown for the coordinator location Please use separate registration forms for each student Make HEWLETT PACKARD COMPANY 1820 Embarcadero Road Palo Alto California 94303 BENCH BRIEFS MAY AUG 1977 Volume 17 Number 3 Service information from Hewlett Packard Company To obtain a qualification form for a free subscription send your request to the above address Reader comments or technical article contributions are welcomed Please send them to the above address attention Bench Briefs Editor Jim Bechtold HP Palo Alto California All rights are reserved No part of Bench Briefs may be reproduced without the express consent of the Editor REGISTRATION INSTRUCTIONS your check payable to Hewlett Packard Company in U S currency Upon receipt of your registration and check we will confirm your enrollment Address Correction Requested WWW HPARCHIVE COM by returning all necessary prestudy material along with a list of nearby motel accommodations and reservation forms Attendees are responsible for their own transportation accommodations and meals Bulk Rate U S Postage PAID Sunnyvale CA Permit No 317 Printed in U S A The Editor may
4. 4 Serials 1643A and below Modifica tion to prevent spike at the beginning of scan 8555A SPECTRUM ANALYZER RF SECTION 8555A 7 Serials 1642A and below Modifica tion to prevent spike at the beginning of scan 8601A SWEEPER GENERATOR 8601A 11 Serials 1612A and below Power supply ripple improvement 8864A INSTRUMENTATION TAPE RECORDER 3964A 8 8864A 7 3968A 8 8868A 8 All serials Calibrator output shorts 3964A 7 8864A 8 3968A 9 8868A 9 All serials Field effect transistor lead configuration 8868A INSTRUMENTATION TAPE RECORDER 3964A 7 8864A 7 3968A 8 8868A 8 All serials Calibrator output shorts 3964A 8 8864A 8 3968A 9 8868A 9 All serials Field effect transistor lead configuration 8951A SYSTEM INTERFACE 8951A 2 Serials 1636A and below Notch filter replacement 9125A B GRAPHIC PLOTTER 7200A 17A 7201A 7A 7202A 17A 9125A B 5A Serials 1620A and below New chart hold autogrip module 9872A GRAPHICS PLOTTER 9872A 2 Serials 1712A and below Autogrip wiring change 59309A HP IB DIGITAL CLOCK 59309A 2 All serials Programming the clock to store and output time correctly 59403A COMMON CARRIER INTERFACE 50403A 1 Serials 1426A00281 and below Modification to improve protection of CCI cir cuits in dedicated line operation 86290A RF PLUG IN 86290A 1A Serials 1450A and below Coupler modulator replacement kit 86601A RF SECTION 86601A 1C Serials 1223A00320 and below 86601A meter replacement kit
5. There are two kinds of source statements ex ecutive instructions which transiate into operating machine code opcode and assembly directives which are useful in documenting the source program but generate no code SIMULATOR A special program that simulates the logical operation of the microprocessor It is designed to execute object programs generated by a cross assembler on a machine other than the one being worked on and is useful for checking and debugging programs prior to committing them to ROM firmware STACK The stack is a block of successive memory locations which is accessible trom one end on a last in first out basis LIFO The stack is co ordinated with the stack pointer which keeps track of storage and retrieval of each byte of information in the stack A stack may be any block of successive information locations in the read write memory SLICE A type of chip architecture which permits the cascading or stack ing of devices to increase word bit size STACK POINTER The stack pointer is co ordinated with the storing and retrieval of information in the stack The stack pointer is decremented by one immediately following the storage in the stack of each byte of information Conversely the stack pointer is incremented by one immediate ly before retrieving each byte of information from the stack The stack pointer may be manipulated for transferring its contents to the Index register or vice versa STATUS WORD REGISTER A
6. VCO has advanced one full cycle and the overflow of this register is used to trigger the pulse remover Now assume that the VCO operates at a frequency such as 10 3 MHz whichis not evenly divisible into 1 0 After one reference period the VCO frequency has advanced 10 3 cycles after two reference periods 20 6 cycles and after three periods 30 9 cycles At this point the phase register contains 0 9 In the fourth reference period the VCO has advanced 41 2 cycles which causes the phase register to overflow in turn triggering the pulse remover Note that when the phase register over flowed it contained a count of 1 2 To preserve the correct relationship be tween pulse removal and the reference frequency the next sequence begins with the excess count of 0 2 loaded in the phase register instead of zero if the VCO frequency was 1 01 MHz Figure 6 shows the elements needed to properly remove a pulse automatically whenever the VCO has advanced one full cycle relative to the reference fre quency The next step is to close the loop Note that the phase detector s output is a sawtooth riding on a dc level The dc portion is the part which Figure 6 Fractional N Loop Showing a Phase Register Used to Trigger the Removal of One VCO Cycle or Pulse represents the proper tune voltage to be fed into the VCO Anything other than dc fed to the VCO will prevent phase lock and cause frequency mod ulation Since the phase re
7. can give your permission Thank You Dwight Hill Rochester N Y By now am sure you have received our letter of permission HP is very concerned about safety and hopes all of our customers will look for the Safety Service Notes described in each issue of Bench Briefs Editor NUT HOLDER Here s a handy tip from Bob Lindsay Group Training Manager and Editor of Computer Sys ar Newsletter from HP s Data Systems Divi on Have you ever had to start a nut on a screw in a corner of an instrument behind the transformer or in some other inaccessible place where you just can t quite reach with your fingers or any thing else The next time that happens try this little trick Bob uses Take a piece of solder and pull a kink in it Lay the kink over the nut and tap it with the ball end of a ball pien hammer The idea is to smash the solder down into the nut to catch a thread you might even try screwing the nut on to the loop of r Once held you can feed the nut to the location and hold it in place long enough to start a few threads j KINK IT j SMASH IT A SHEEP PUZZLE This punn is reprinted from The Grapevine an HP Santa Rosa Div employee newsletter Two brothers sold a flock of sheep which they owned in partnership For each sheep they re ceived as many rubles as the number of sheep in the original flock The money was divided in the following manner First the older brother took 10 rubles then the younge
8. enn II De Broglie will delight in the light equation h but shudder we can hear Maxwell turn in his grave i is totally wrong a sloppy V crept in where a del should be legally placed At any rate with barely a C for a passing grade to your prinTeR match i with 10 7 not V And last but not least the lever formula cleverly or sloppily allows for a short lever small x and a long one cap X2 so let j and 8 join hands SiINcErElY YOurS S Kurni Professor Albuquerque New Mexico You are absolutely right Mr Karni am passing your letter on to Doubleday the original typesetter Incidentally Mr Karni correctly matched up the answers before the January February issue of Bench Briefs came out His letter was postmarked January 19 and received it April 7 That s why the delay in acknowledgement Editor What They Mean SAFETY SYMBOLS IN MANUALS Hewlett Packard instruments and their operating and service manuals use a standardized set of safety symbols to convey safety information to the user They are provided here as a reference to our customers When used in the manual these symbols will be de scribed in terms related to the specific application Instruction manual symbol the product will be marked with this symbol when it is necessary for the user to refer to the instruction manual in order to protect against damage to the instrument 4 Indicates dangerous
9. of comparing different makes of microprocessors A flow chart in assembly language is written out tor each microprocessor and the execution of the benchmark by each unit is evaluated on paper It is not necessary to use hardware to measure Capability by benchmark BIDIRECTIONAL A term applied to a port or bus line that can be used to transfer data in either direction BINARY A system of numbers using 2 as a base in contrast to the deci mal system which uses 10 as a base The binary system requires only two symbols 0 and 1 Two is expressed in binary by the number 10 read one zero Each digit after the initial 1 is multiplied by the base 2 Hence the following table expresses the first ten numbers in decimal and binary Decimal Binary Decimal Binary 0 0 5 101 1 1 6 110 2 10 7 111 3 11 8 1000 4 100 9 1001 BRANCH Refers to the capability of a microprocessor to modily the function or program sequence Such modification depends on the actual content of the data being processed at any given instant BREAKPOINT A program point indicated by a breakpoint flag which invites interruption to give the user the opportunity to check his program betore continuing to its completion BUFFER A circuit inserted between other circuit elements to prevent interactions to match impedances to supply additional drive capability or to delay rate of information flow Buffers may be inverting or non in venting BUS DRIVER An integrated circuit which is add
10. the control tunc tions of the CPU It is responsible tor decoding microprogrammed instruc tions and then generating the internal control signals that perform the operations requested CONTROL BUS Conveys a mixture of signals which regulate system opera tion These traffic signals are commands which may also originate in peripherals for transfer to the CPU or the reverse CONTROL PROGRAM The Control Program is a sequence of instructions that will guide the CPU through the various operations it must perform This program is stored permanently in ROM memory where it can be accessed by the CPU during operations Repanied Irom Microproce WAN HPAROHIVE COMy Schweber Electronic Corporation CPU Central Processing Unit The heart of any computer system Bas ically the CPU is made up of storage elements called registers compu tational circuits in the ALU the Control Block and I O As soon as LS technology was abie to build a CPU on an IC chip the microprocessor became a reality The one chip microprocessors have limited storage space so memory implementation is added in modular fashion Most current microprocessors consist of a set of chips one or two of which form the CPU CROM Control Read Only Memory This is a major component in the control block of some microprocessors It is a ROM which has been microprogrammed to decode control logic CROSS ASSEMBLER When the program is assembled by the same micro processor that it
11. very much like a Capacitor which explains why MOS is slower than bipolar since the capacitor sandwich must charge up before current can flow The three great advantages of MOS are its process sim plicity because of reduced fabrication stages the savings in chip real estate resulting in functional density and the ease of interconnection on chip These qualities enabled MOS to break the LSI barrier something bipolar is just beginning to achieve The hand held calculator and the microproces sor are triumphs of MOS LS technology MICROPROCESSOR The microprocessor is a Central Processing Unit fabricated on one or two chips While no standard design is visible in existing units a number of well delineated areas are present in all of them Arithmetic amp Logic Unit Control Block and Register Array When joined to a memory storage system the resulting combination is referred to in today s usage as a Microprocessor It should be added that each microprocessor is supplied with an Instruction Set and this software manual may be just as important to the user as the hardware MULTIPLEXING Multiplexing describes a process of transmitting more than one signal at a time over a single link route or channel Of the two methods in use one frequency shares the bandwidth of a channel in the same way hurdlers run and jump in their assigned lanes thus permitting many contestants to compete simultaneously on the same track The second way is to time s
12. voltage termi nals fed from the interior by volt age exceeding 1000 volts must be so marked a Protective conductor terminal For pro tection against electrical shock in case SERVICE INFORMATION of a fault Used with field wiring ter minals to indicate the terminal which must be connected to ground before operating equipment Low noise or noiseless clean ground earth terminal Used for a signal common as well as providing protec tion against electrical shock in case of a fault A terminal marked with this symbol must be connected to ground in the manner described in the installa tion operating manual and before operating the equipment tee Frame or chassis terminal A connec tion to the frame chassis of the equip ment which normally includes all ex posed metal structures NS Alternating current power line Direct current power line Ny Alternating or direct current power line The WARNING sign denotes a haz ard It calls attention to a pro cedure practice or the like which if not correctly performed or adhered to could result in personal injury CAUTION The CAUTION sign denotes a haz ard It calls attention to an operat ing procedure practice or the like which if not correctly performed or ad hered to could result in damage to or destruction of part or all of the product In other words violating this restriction will wreak havoc upon the user
13. will run on the program that performs the assembly is relerred to simply as an assembler It the program is assembled by some other microprocessor the process is referred to as cross assembly Oc casionally the phrase native assembler will be used to distinguish it from a cross assembier D DAISY CHAIN A bus line which is interconnected with units in such a way that the signal passes from one unit to the next in serial fashion The architecture of the Fairchild F 8 provides an example of daisy chained memory chips Each chip connects to its neighbors to accomplish daisy Chaining of interrupt priorities beginning with the chip closest to the CPU DATA BUS The microprocessor communicates internally and externally by means of the data bus It is bidirectional and can transfer data to and trom the CPU memory storage and peripheral devices DATA COUNTER See Program Counter DATA DOMAIN Analysis of logic tunction or algorithmic state machines as a function of the data sequence or the state space sequence Data is used in the generic sense the data at any given event time or state space defines the status of a machine at that point e g address instruction operation and status words as well as data words in the sense of operator and or operand The data domain is distinguished from the classical electronic analysis domains of time and frequency Analysis of parametric behavior as a function of time f 1s considered time do
14. 10V Liechtenstein 220V Seychelles 220V Luxembourg 110 220V Sierra Leone 220V Macao 110 220V Singapore 110 220V t Madeira 220V Somalia 110 220V Majorca 110V South Africa 220V Malagasy Rep 220V South Korea _ 220V Malawi 220V Spain 110 220V Malaysia 220V Sri Lanka Mses 110 220V Ceylon 220V Malta 220V Sudan 220V Martinique 110 220V Surinam 110 220V Mauritania 220V Swaziland v Mexico 110 220V t Sweden 110 220V Monaco 110 220V Switzerland 110 220V Montserrat V Syria 110 220V Morocco 110 220V Tahiti 110 220V Mozambique 220V Taiwan 110 220V Nepal 220V Tanzania 220V Netherlands 110 220V Tobago 110 220V Neth Antilles 110 220V Togo 110 220V Nevis 220V Tonga 220V New Caledonia 220V Trinidad 110 220V New Guinea 220V Tunisia 110 220V New Hebrides 220V Turkey 110 220V New Zealand 220V Turks amp Nicaragua 110 220V Caicos 110V Niger 220V Uganda 220V Nigeria 220V Upper Volta 220V Northern ireland 220V Uruguay 220V sss 220V United Arab Okinawa 110V Emirates 220V Oman 220V USA 110V Pakistan 220V be 110 220V Panama 110V U S Virgin 1 110V Paraguay 220V Venezuela 110 220V Peru 220V Vietnam 110 220V Philippines 170 220V Wales 220V Poland 110 220V Yemen ssas 220V Portugal 110 220V Yugoslavia 220V Puerto Rico 110V Zaire 220V Qatar 220V Zambia 220V Denotes countries in w
15. ESSOR BUZZ WORDS The third digit of the octal number represents 64 s so multiply 1 x 64 64 The sum is the decimal number 125 OPERAND A quantity on which a mathematical operation is performed One of the instruction fields in an addressing statement Usually the state ment consists of an operator and an operand The operator may indicate an add instruction the operand will indicate what is to be added OVERFLOW Overflow results when an arithmetic operation generates a quantity beyond the capacity of the register Also referred to as arith metical overflow An overflow status bit in the condition code register can be checked to determine if the previous operation caused an overflow OPERATING CODE Opcode Source stalements which generate ma chine codes after assembly are reterred to as operating codes P PARALLEL OPERATION Processing all the digits of a word or byte simultaneously by transmitting each digit on a separate channel or bus line PARTY LINE Party line as used in its telephone sense to indicate a large number of devices connected to a single line originating in the CPU PIPELINE Computers which execute serial programs only are reterred to as pipeline computers PLA Programmed Logic Arrays The PLA is an orderly arrangement of logical AND and logical OR functions Its application is very much like a glorified ROM It is primarily a combinational logic device POLLING Polling is the method used to identity the source
16. El Salvador 110V Bahamas 190 220V Ethiopia 110 220V Bahrain 220V a SOO d Bangladesh 220V Finland 220V Barbados 110 220V 110 220V Belgium 110 220V French Guiana 110 220V Bermuda 110 220V Gabon 220V Bhutan 220V Gambia 220V Bolivia 110 220V Germany 110 220V Bonaire 110 220V Ghana 220V Botswana 220V Gibraltar 220V t Srazil n 110 220V Great Britain v Brit Honduras 110 220V tGreece _ 110 220V Brit Virgin 110 220V Greeniand 220V Bulgaria 110 220V Grenada 220V Burma 220V Grenadines 220V Burundi 220V Guadeloupe 110 220V Cambodia 110 220V Guatemala 110 220V Cameroon 110 220V Guinea Canada 110 220V Guyana 110 220V Canal Zone 110 220V Halti 110 220V Canary 110 220V Honduras 110 220V L 110V Hong Kong 220V Cen African Hungary 220V 220V 220V tindia 220V Channel Brit 220V iT 110 220V Tt Chile v iran v China 220V iraq 220V Colombia 110V ireland 220V Costa Rica 110 220V isle of Man 220V SERVICE INFORMATION Isreal 220V Rhodesia v Italy 110 220V Romania 110 220V Ivory Coast 220V Rwanda 220V Jamaica 110 220V Saba 110 220V Japan 110V St Barthelemy 220V Jordan 220V St Eustatius 110 220V Kenya 220V St Kitts 220V Kuwait 220V St Lucia 220V Laos 110 220V St Maarten 110 220V Lebanon 110 220V St Vincent v Lesotho 220V Saudi Arabia 110 220V Liberia _ 110 220V Scotland _ 220V Libya 110 220V Senegal 1
17. HAS UNAMBIGUOUS DISPLAY by S Jayasimha Prasad and M R Muralidharan India Institute of Technology Madras India Reprinted from Electronics March 3 1977 Copyright McGraw Hill Inc 1977 It usually takes a little time to interpret the display of most logic probes But this tester flashes a totally unambigu ous 0 or 1 or on its seven segment display the question mark indicating any voltage level not within the logic thresholds The circuit built around transistor transistor logic NAND gates is shown in the figure The output character display is controlled by the logic of input transistors Q and Qo If an input of less than 0 8 v is encountered both transistors are off and the display is gated to indicate a 0 For an input greater than 2 0 v both transistors are on and the display indicates a 1 ALL NANO GATES 7400 ALL TRANSISTORS MULLARD BC 149C AMPEREX A749C OR EQUIVALENT eave Vi aay IOR HIGH Unquermonatly lopes TTL terer diupteys O tor iow bevel 1 for F Migh level and lor an open circust or ogas ivesi as shown ia Vin gt t0 V tabe Thesshoidi ore st by trenman in the input eirewit and may be changed t0 mt pertsiar needs For an input that lies between 0 8 v and 2 0 v Q is on while Qz is off and the NAND gating causes a question mark to be indicated on the display A high impedance at the input registers a similar output The logic thresholds being set by the voltage drops of th
18. LED displays 3556A PSOPHOMETER 3556A U 1003 Serial numbers 1547U and below New battery modification 37028 IF BB RECEIVER 3702B 34A Serials 1642U 01746 and below Modification to prevent D C offset on I F display 3702Z DEMODULATOR DISPLAY 3702Z 8 Serials 1119U 01176 and below Preferred replacement for rectifier assy A24 3745A B SELECTIVE LEVEL MEASURING SET 3745A B 6A Serials 1647U and below Inter mittent operation of 5 2V power supply 3745A B 8 Serials 1690U and below Re placement A107 CPU I O assembly 3745A B 9 Serials 1538U and below Protec tion of processor filter contro outputs 3745A B 10 Serials 1715U and below Re duction of 10MHz and 20MHz spurious sig nals when using the 15580A active probe accessory 3770A AMPLITUDE DELAY DISTORTION ANALYSER 3770A 33 All serials Incorrect part number of power switch 3770B TELEPHONE LINE ANALYSER 3770B 8 Serials U 00166 and below Ensuring enough range in A12 retransmission adjust ment 3770B 9 All serials Incorrect part number of power switch WWW HPARCHIVE COM SERVICE NOTES 3964A INSTRUMENTATION TAPE RECORDER 3964A 7 8864A 7 3968A 8 8868A 8 All serials Calibrator output shorts 3964A 8 8864A 8 3968A 9 8868A 9 All serial numbers Field effect transistor lead configuration 3968A INSTRUMENTATION TAPE RECORDER 3964A 7 8864A 7 3968A 8 8868A 8 All serials Calibrator output shorts 3964A 8 8864A 8 3968A 9 8868A 9 All
19. N TAPE RECORDER OWNERS 0htone gs Soet Sesesi A y HP Model 3964A 3968A 8864A 8868A Instrumentation Tape Record ers received a new push button power switch starting with serial prefix 1706A This change is described in Service Note 3964A 6 3968A 7 8864A 6 8868 7 If your machine has one of the older toggle switches and it fails you can order a new pushbutton type with a higher surge current rating from the following list Model HP Part No 3964A 03964 60060 3964A 009 8864A white panel 03964 60061 3968A 03968 60060 3968A 009 8868A white panel 03968 60061 AUTOMATIC AUTORANGING There may be a time when you might use an autoranging voltmeter on the ohms scale to measure front to back ratio on transistors All at once the meter begins switching back and forth between ranges What s wrong Actually nothing It s a peculiarity that sometimes takes place when measur ing a diode device transistor junction with a non inear load line What is happening is that since the load line is not linear and the meter puts out a different current on each ohms range the voltage current ration is constantly changing When the current becomes excess the meter autoranges As the current drops the meter autoranges again The solution is to switch the meter to a fixed scale or change to a multi meter THINK METRIC Part of the metric system we are facing involves temperature measurement Here is a little h
20. OT to mention a few examples Each function can be translated into a switching circuit more commonly referred to as a gate Since a switch or gale has only two states open or closed it makes possible the application of binary numbers for the solution of problems The basic logic functions obtained from gate cir cuits is the foundation of complex computing machines LOGIC ANALYZERS State An instrument designed to operate synchronously with a clock or strobe trom the system under test Used primarily to determine the state ot data transactions in relation to that clock Time An instrument designed to operate asynchronously with the system under test using an internal clock Used to determine the time relation ship between data transitions LOOK AHEAD 1 A feature of the CPU which allows the machine to mask an interrupt request until the following instruction has been com pleted 2 A teature of adder circuits and ALUs which allow these devices to look ahead to see that all carrys generated are available for addition LOOPING Repetition of instructions at delayed speeds until a final value is determined as in a weight scale indication is called looping The looped repetitions are usually frozen into a ROM memory location and then jumped to when needed Looping also occurs when the CPU is in a wait condition LSI Large Scale integration A the beginning of the LSI era a count of 100 gates qualified for LSL Today an 8 bit CPU can be f
21. RMATION specified would be meaningless in a failed mode Since troubleshooting tables usually refer to a high or low output condition fault finding is reduced to adjusting the voltage control to its mid point opening the feedback loop then driving each stage into conduction or cutoff by either shorting or opening the previous stage If the stage can be turned on and off there is a 99 chance it will also work in between those points where it s sup posed to If the stage doesn t react as expected then you have effectively narrowed the search down to a few components If the problem is more subtle try measuring the offset voltage across the comparison amplifier If the sum ming point voltage is near zero then the amplifier is following the program ming as it should If the summing point voltage is not zero it may be possible to force it there with the voltage control The power supply may appear to work but exces sive current drawn through the voltage control circuit will not allow the power supply to meet its performance tests John Whidden service engineer at the New Jersey Division joined HP in 1961 and became involved with power supply service and applications for field service and customer training John spends his spare time in photogra phy and TV radio repair He is married and has three children WWW HPARCHIVE COM le oO NEW IDEAS LOGIC TESTER
22. abricated on a single chip MACHINE LANGUAGE The only language the microprocessor can under stand is binary All other programming languages must be transiated into binary code before entering the processor and decoded back into the original language after leaving it MACRO COMMAND A program entity formed by a string of standard but related commands which are put into effect by means of a single macro command Any group of frequently used commands can be combined into a macro command The many become one MACROLOGIC A group of LS chips which when combined will form a microprocessor These devices can be arranged to permit the user to microprogram his own microprocessor In such an arrangement he is not limited to a fixed instruction se and is able to build his own instruction set MAIL BOX The Mail Box is a set of locations in a common RAM storage area reserved for data addressed to specific peripheral devices as well as other microprocessors in the immediate environment Such an arrangement enables the co ordinator CPU and the supplementary microprocessors to transfer data among themselves in an orderly fashion with minimal hard ware TM Macrologic is a Fawchild trademark WWW HPARCHIVE COM MNEMONIC CODE These are designed to assist the human memory The microprocessor language consists of binary words which are a series of 0 s and l s making it difficult for the programmer to remember the instruc tions corresponding t
23. ase 1700A OSCILLOSCOPE 1700A 7 All serials Handle replacement kit 1700B OSCILLOSCOPE 1700B 3 Handle replacement kit 1701A OSCILLOSCOPE 1701A 7 All serials Handle seplacement kit 1701B OSCILLOSCOPE 1701B 2 Handle replacement kit 1702A OSCILLOSCOPE 1702A 3 Handle replacement kit 1703A OSCILLOSCOPE 1703A 7 Handle replacement kit SERVICE NOTES 1706A B OSCILLOSCOPE 1706A B 1 All serials Handle replacement kit 1707A OSCILLOSCOPE 1707A 5 All serials Handle replacement kit 1707B OSCILLOSCOPE 1707B 6 Handie replacement kit 1710A OSCILLOSCOPE 1710A 6 All serials Handle replacement kit 1710B OSCILLOSCOPE 1710B 13A All serials Improved focus resistors 1712A OSCILLOSCOPE 1712A 12A All serials Improved focus resistors 1720A OSCILLOSCOPE 1720A 16A All serials Improved focus resistors 1722A OSCILLOSCOPE 1722A 16A All serials Improved focus resistors 3435A B DIGITAL MULTIMETER 3435A 1A All serials Replacement part numbers for LED displays 3465A MULTIMETER 3465A 3A Serials prior to 1546A01501 Replacement of fine line resistor pack A1R75 3465A 4A All serials Replacement part numbers for LED displays 3465B DIGITAL MULTIMETER 3465B 1A All serials Replacement part numbers for LED displays 3495A SCANNER 3495A 2 Modification to ease insertion and improve alignment with 3495A Mainframe 3551A TRANSMISSION TEST SET 3551A 5 All serials Replacement part numbers for
24. ate boxes below and re turn this form separately to one of the following addresses For European customers ONLY Hewlett Packard Central Mailing Dept P O Box 529 Van Hueven Goedhartlaan 121 AMSTELVEEN 1134 Netherlands All other customers Hewlett Packard 1820 Embarcadero Road Palo Alto California 94303 Name Company Name Address oy T O 197A 7 oO 1710B 13A O 5150A 1 O 745A 10A O 1712A 12A oO 5150A 2 1745A 12A S O 1720A 16A O 5304A 1 O 745A 13A O 1722A 16A O 5328A 3 o 1332A 5 O 3435A 1A O 5328A 4 O 1333A 1 O 3465A 3A 5 5340A 8 O 1335A 2 C 3465A 4A O 5340A 9 O 1335A 3 O 3465B 1A O 5340A 10 O 1645A 6 O 3495A 2 0 7200A 17A 7201A 7A oO 1645A 7 0 3551A 5 7202A 17A 9125A B 5A O 1700A 7 O 3556A U 1003 O 8552A 12 O 1700B 7 O 3702B 34A O 8552B 12 O 1701A 7 0 37022 8 O 8554B 4 O 1701B 2 O 3745A B 6A O 8555A 7 O 1702A 3 O 3745A B 8 O 8601A 11 O 1703A 7 DO 3745A B 9 O 8951A 2 C 1706A B 1 O 3745A B 10 O 9872A 2 O 1707A 5 O 3770A 33 O 59309A 2 O 17078 6 O 37708 8 O 59403A 1 O 1710A 6 DO 37708 9 O 86290A 1A O 86601A 1C O 3964A 7 3968A 8 8864A 7 8868A 8 O 3964A 8 3968A 9 8864A 9 8868A 9 O 5045A 1 WWW HPARCHIVE COM SEMINAR REGISTRATION U S SEMINAR REGISTRATION FORM COORDINATOR COURSE DATE COST LOCATION 8640 8660 5 435 Aug 29 350 Student Bill Whitney 436 Sept 2 1501 Page Mill Road 8480 Palo Alto CA 94304 11683 o s4RESEHED WLEDstucent Pete Johnson W 120 Century Road Paramus N J
25. ates Centigrade became Celsius at the 1948 meeting of the General Confer ence a difference in name only The principal reasons for the change were a desire for uniformity in some parts of WWW HPARCHIVE COM Europe it was already called Celsius and a desire to honor the originator of the scale Comparison between the two scales is not necessary in learning Celsius temperature just learn a handful of temperatures which become points of reference In addition to the freezing 0 C and boiling points 100 C of water know what the temperature is on a typical early morning for where you live it could be 10 C in the summer and 5 C in the winter 20 C is a comfortable room temperature 30 C is getting warm and about time to turn the air conditioning on 37 C is normal body temperature 40 C for body temperature is alarming Get a metric thermometer and place it by your desk or outside and estimate the temperature at different times of the day It is an easy way to start to think metric Always remember that it s best not to convert back to Fahrenheit Learn your temperature in Celsius and stick with it MICROPROCESSOR BUZZ WORDS MICROPROCESSOR BUZZ WORDS The Seventies will probably be known as the era of the microprocessor it will become a decade that will see the unprecedented growth of a product which will change the world of electro mechanics electronic testing and the communications in
26. ates Information may be written in or read out in the same rapid way RANDOM LOGIC DESIGN Designing a system using discrete logic cir cuits Numerous gates are required to implement the logic equations until the problem is solved Even then the design is not completed until all redundant gates are weeded out Random logic design is no guarantee of optimum gate count REAL TIME OPERATION Data processing technique used to allow the machine to utilize information as it becomes available as opposed to batch processing at a time unrelated to the time the information was generated REGISTER A register is a memory on a smaller scale The words stored therein may involve arithmetical logical or transferral operations Storage in registers may be temporary but even more important is their acces sibility by the CPU The number of registers in a microprocessor is con sidered one of the most important features of its architecture RELATIVE ADDRESSING The relative addressing mode specifies a mem ory location in the CPU s Program Location Counter register This addres sing mode is used for Branch instructions in which case an opcode is added to the Relative Address to complete the branching instruction ROM Read Only Memory In its virgin state the ROM consists of a mosaic of undifferentiated cells One type of ROM is programmed by mask pattern as part of the last manufacturing stage Another more popular type better known as P ROM is pr
27. be telephoned at 415 493 1501 Extension 4253 C
28. dustry Its effect on our daily lives will be comparable to that of the computer it takes about 10 years for new words to find their way into the dic tionary Waiting so long to learn the new meaning of a word in so fast moving an industry as electronics could have a blighting effect on the education of those who wish to keep up to date Schweber Electronics periodically publishes BUZZ WORDS a glossary of words that are the currency of the industry words thal mirror the present state of the art and give you a peek into the future Scanning these buzz words you will soon realize that although the tech nology is new the words are in common everyday use but technology has given them uncommon meanings and only those in the know can communicate with them PORT which we know as an embarkation point for ships becomes the microprocessors contact with the outside world BUS a convenient vehicle tor picking up and discharging passengers becomes an electrical conductor inside the microprocessor which facilitates data flow DAISY CHAIN a circular group of people holding hands becomes a group of devices interconnected in such a way that the data flows from one unit to the next in serial fashion Hewlett Packard thanks Schweber Electronics Corporation for their per mission to reprint these Microprocessor Buzz Words A ABBREVIATED ADDRESSING A modification of the Direct Address mode which uses only part of the full address and provides a faste
29. e 745A 12A S Modification Kit 00745 89503 Troubleshooting Tip DC REGULATED POWER SUPPLIES by John Whidden HP New Jersey Division Most HP power supply schematics sel dom show operating voltages on tran sistors inside the feedback loop The reason is that a DC regulated power supply is a closed loop device when a component fails all voltages inside that loop go to one extreme or another Therefore any closed loop voltages A SERVICE MANUAL FOR THE 8660 SIGNAL GENERATOR by Gary Sprader HP Stanford Park Div TE 9 PEELE 9 EEKE a anapa gt F A new manual that explains the 8660 Synthesized Signal Generator system from a service point of view is now available This manual begins with an explanation of phase lock loops and how they are used in the 8660 and continues with the functional modules and plug ins The book which is really a service training course in itself is de signed for someone not familiar with the 8660 To obtain a copy contact your HP Sales and Service office and order HP part number 08660 90072 DO YOU KNOW what IC manufacturers mean by SSI MSI LSI and GSI SSI Small Scale Integration fewer than 12 logic gates on a chip MSI Medium Scale Integration 12 100 logic gates on a chip LSI Large Scale Integration 100 1000 logic gates on a chip GSI Grand Scale Integration over 1000 logic gates on a chip E SERVICE INFO
30. e transistors can be tailored to suit other needs Transis tors Q3 Qs which determine the logic 1 threshold may be replaced with an appropriate number of diodes and diodes may even be added in the base circuit of Q to raise the logic 0 threshold Resistors R and R2 limit the input current and R3 R limit the currents to the display which may be any low power seven segment light emitting diode unit DIRECT READING OHMMETER NEEDS NO CALIBRATION by V Ramprakash Electronic Systems Research Madurai India Reprinted from Electronics November 11 1976 Copyright McGraw Hill Inc 1976 A direct reading ohmmeter with a linear scale can be made by connect ing an operational amplifier a milli ammeter a zener diode and some resistors as shown in the circuit diagram This ohmmeter does not require calibration is self zeroing and is insensitive to the supply voltage The value of an unknown resistor is measured by connecting it as Rx The reading on the milliammeter Im is then Rx Re where Re is the resistance of a known standard resistor in the circuit _ The current through the meter equals Vo Vz Rm where Vo is the voltage at the output of the op amp Vz is the drop across the zener diode 3 v and Rm is the resistance in the meter circuit here Rm is 2 9 0 1 kilohms Since the voltages at the inverting and noninvert ing input terminals of the op amp must be equal Vo Re Re Rx mu
31. ed to the data bus system to tacilitate proper drive to the CPU when several memories are tied to the data bus line These are necessary because of capacitive loading which slows down the data rate and prevents proper time se quencing of microprocessor operation BUS SYSTEM A network of paths inside the microprocessor which facili tate data flow The important busses in a microprocessor are identified as Data Bus Address Bus and Contro Bus BYTE Indicates a pre determined number of consecutive bits treated as an entity For example 4 bit or 8 bit bytes Word and Byte are used inter changeably Cc CLOCK A generator of pulses which controls the timing of switching circuits in a microprocessor Clock frequency is not the only criterion of data manipulation speed Hardware architecture and programming skill are more important Clocks are a requisite for most microprocessors and multiple phased clocks are common in MOS processors COMBINATIONAL LOGIC A circuit arrangement in which the output Stale is determined by the present state of the input Also called Com binatorial logic See also Sequential Logic COMPILERS Compilers translate higher level languages into machine code CONDITION CODE Refers to a limited group of program conditions such as carry borrow overflow etc which are pertinent to the execution of instructions The codes are contained in a Condition Codes Register CONTROL BLOCK This is the circuitry which performs
32. ement is the reverse of the negative standard binary plus 1 127 in standard binary 11111111 To form the 2 s complement of 127 First reverse all the digits except the sign 10000000 Then add 1 1 10000001 127 in 2 s complement UART Universal Asynchronous Receiver Transmitter This device will interlace a word parallel controller or data terminal to a bit serial communication network CUSTOMER SERVICE SEMINARS v VECTOR INTERRUPT This term is used to describe a microprocessor system in which each interrupt both internal and external have their own uniquely recognizable address This enables the microprocessor to perform a set of specified operations which are pre programmed by the user to handle each interrupt in a distinctively different manner w WORD A group of characters treated as a unit and given a single location in computer memory Presumably a byte is a group of bits in contrast to a word which is a group of numeric and or alphabetic characters and symbols but the two words are used interchangeably more often than not X X BUS See Address Bus For More intormabon Cail Your Local HP Sales Office or in US East 301 948 6370 Midwest 312 677 0400 South 404 434 4000 Wesi 213 877 1282 Or Wmte Hewlett Packard 1501 Page Mill Road Palo Allo California 94304 in Europe Post Office Box 85 CH 1217 Meynn 2 Geneva Switzerland in Japan YHP 1 59 1 Yoyogi Shibuya Ku Tokyo 151 S
33. ess differs in different models and some use several methods to accomplish OMA EXECUTION TIME Usually expressed in clock cycles necessary to carry out an instruction Since the clock frequency ts known the actual time can be calculated Clock Ilrequencies can be varied EXTENDED ADDRESSING Refers to an addressing mode that can reach any place in memory See also Direct Addressing F FETCH To go after and return with things In a microprocessor the objects fetched are instructions which are entered in the instruction register The next or a later step in the program will cause the machine to execute what it was programmed to do with the fetched instructions Otten reterred to as an instruction fetch MICROPROCESSOR BUZZ WORDS FIELDS A source statement is made up of a number of code fields usually four which are acceptable by the assembler The lour fields may connote Label Operator Operand and Comment Fields are also appli cable to data Storage The eight bits stored in a memory location might contain two 4 bit fields or eight 1 bit fields etc FIRMWARE Software instructions which have been permanently frozen into a ROM are sometimes referred to as Firmware FLAG BIT An information bit which indicates some torm of demarcation has been reached such as overflow or carry Also an indicator of special conditions such as interrupts FLOW CHART OR FLOW DIAGRAM A sequence of operations charted with the aid of symbols dia
34. gister is in cremented each reference period its contents represent an instantaneous fractional sum which grows until one cycle of phase advancement has oc curred The contents of the phase reg ister as viewed with respect to time is shown in Figure 7 The contents of the phase register can be represented by a staircase ramp resetting each time a pulse is removed Note that the phase register when viewed graphically has the same characteristics as the saw tooth output from the phase detector i H i Figure 7 A Pictorial View of the Contents of the Phase Register Figure 8 shows the addition of a digital to analog converter DAC to the output of the phase register By converting the contents of the phase register into voltage through the DAC the sawtooth output of the phase detec tor can be approximated The next step is to smooth the output of the DAC to WWW HPARCHIVE COM Ken Jessen received his BSEE and MBA from the University of Utah before joining HP in 1965 Ken is in Customer Service at the Loveland Colorado Division where he is Service Manager for the sources and analyzer product line Spare time activities include writing both technical articles for trade publications as well as historical articles on Colorado rail transporta tion for local newspapers Ken is also a member of the Loveland Public Library board of directors remove the stairs invert it and sum it with the output
35. grams or other representations to indicate an executive program Flowcharts enable the designer to visualize the procedure necessary for each item on the program A compiete flowchart leads directly to the final code H HANDSHAKING A colloquia term which describes the method used by a modem to establish contact with another Modem at the other end of a telephone line Often used interchangeably with butfering and inter facing but with a fine line of difference in which handshaking implies a direct package to package connection regardless of functional circuitry HARDWARE The individual components of a circuit both passive and active have long been characterized as hardware in the jargon of the engineer Today any piece of data processing equipment is informally called hardware HARD WIRED LOGIC Random Logic design solutions require intercon nection of numerous integrated circuits representing the logic elements An example ot hard wired logic is the use of a hand wired diode matrix instead of a ROM These interconnections whether done with soldering won of by printed circuit board are referred to as hard wired logic in contrast to the software solutions achieved by a programmed ROM or Microprocessor HIGH LEVEL LANGUAGE This is a problern oriented programming lan guage as distinguished from a machine oriented programming language The former s instruction approach is closer to the needs of the problems to be handled than the language of t
36. group ol binary numbers which informs the user of the present condition of the microprocessor In the Fairchild F8 the Status Register provides the following five pieces of information plus or minus sign of the value in Accumulator overtiow indication carry bit all zero s in accumulator and interrupt bit status STORAGE The word storage is used interchangeably with memory In tact it has been recommended as the preferred term by people who would rather not imply that the computer has any relationship with the human brain SUBROUTINE Part of a master routine which may be used at will in a variety of master routines The object of a Branch or Jump command T THROUGHPUT The speed with which problems or segments of problems are performed is called Throughput Defined in this way it is obvious that throughput will vary trom application to application As an index of speed throughput is meaningful only in terms of your own application TIME DOMAIN See Data Domain for comparative definition TWO S COMPLEMENT NUMBERS The ALU performs standard binary addition using the 2 s complement numbering system to represent both positive and negative numbers The positive numbers in 2 s complement representation are identical to the positive numbers in standard binary 127 in standard binary 01111111 127 in 2 s complement 01111111 Note that the eighth or most significant digit indicates the sign 0 plus minus However the negative 2 s compl
37. hare multiple signals in the same way that pole vaulters jump over the same bar one after the other The two methods may be described as parallel and serial processing Time sharing may nol seem simultaneous but it should be remembered that the signal speed is so fast that it is possible to multiplex four different numbers through a single decoder driver and have them appear on four different displays without a flicker to disturb the eye NESTING Nesting is referred to when a subroutine is enclosed inside a larger routine bul is not necessarily part of the outer routine A series of looping instructions may be nested within each other o OBJECT PROGRAM The end result of the source language program after it has been translated inta machine language OCTAL Whole numbers in positional notation using 8 as a base The decimal or base 10 number 125 becomes 175 in octal or base 8 Here is a Convenient way to convert a decimal number into an octal number Divide the decimal number by amp The answer is 15 At and 5 lett over 8 155 Divide the answer 15 by 8 again The answer is 1 8 125 and 7 left over The octal number is 175 To prove your answer is correct do the following 5x 1 Arrange the octal number vertically withthe least 7x B 56 significant digit on top 1x64 64 The least significant digit represents one s so 125 multiply 5x1 5 The next digit in the octal number represents 8 s so multiply 7 x 8 56 MICROPROC
38. hat the VCO is operating at a fractional multiple 10 1 of the refer ence signal It would be impossible to close this loop if it were a divide by N loop because the phase detector com pares the reference signal to the divide by N signal and then generates a dc level equivalent to the phase dif ference That is the VCO is not operat ing at an integral number times the ref erence signal but rather as a fractional component this means the phase of the VCO is advancing Since the phase of the VCO signal divided by 10 is advancing relative to the phase of the reference signal the phase detector puts out an ever increasing dc level In the normal case closed divide by N loop the phase detector s output would be used as the tune voltage back to the VCO forcing its frequency to drop from 1 01 MHz to 1 00 MHz In the frac tional N loop the phase is allowed to advance and the phase detector out puts a ramp Reference periods are defined using Figure 3 as follows While the refer ence signal goes through one period the VCO operating 10 1 times as fast FRACTIONAL N goes through 10 1 cycles To put this another way the VCO advances one tenth of a cycle relative to its integral part for every reference period After the passage of two reference periods the VCO has gone 20 2 cycles and after ten reference periods the VCO has advanced 101 cycles 100 cycles plus one extra cycle which represents the fractional component
39. he machine on which they are to be implemented HEXADECIMAL Whole numbers in positional notation using 16 as a base See Octal and compare Since there are 16 hexadecimal digits 0 through 15 and there are only ten numerical digits 0 through 9 an additional six digits representing 10 through 15 must be introduced Re course is had to the alphabet to provide the extra digits Hence the leas significamt hexadecimal digits read 0 1 2 3 4 5 6 7 8 9 A B C D E F The decimal number 16 becomes the hexadecimal number 10 The decimal number 26 becomes the hexadecimal number 1A I IMMEDIATE ADDRESSING In this mode of addressing the operand con tains the value to be operated on and no address reference is required INCREMENT and Decrement These two words are software operations most offen associated with the stack and stack pointer Bytes of informa tion are stored in the stack register at the addresses contained in the stack pointer The stack pointer is decremented after each byte of informa tion is entered into the stack it is incremented after each byte is removed from the stack The terms can also refer to any addressable register INDEX REGISTER The Index Register contains address information sub ject to modification by the Control Block without affecting the instruction in the memory The IR information is available for loading onto the stack pointer when needed INDIRECT ADDRESSING Addressing a memory location which contai
40. hich plugs with 3 square pins are used in whole or part tCountries using DC in certain areas FAST L C MEASUREMENTS Here is a very old but convenient method for determining the value of unmarked capacitors or inductors using instruments commonly found in most maintenance shops and labs The method is based on the axiom that when an impedance is fed from a constant current source the voltage across the impedance is a function of the magnitude of the impedance See figure below To calibrate the setup connect a known value capacitor or inductor to the TEST terminals Set the oscillator to the desired frequency with maximum output For example used 10 Hertz to calibrate on a 1 0 mic rofarad capacitor and 100kHz to cali brate on a 100pF capacitor Set the VTVM to the 0 1 volt range and adjust the 100 ohm resistor for an indication onthe VTVM that agrees with the value of the known capacitor or inductor Example 100pf 0 1v 50pf 0 5v etc or the reciprocal for a known in ductor Connect the unknown to TEST and read directly capacitance or recip rocal of inductance NOTE For best accuracy the ratio of X to R should be 100 1 or greater EQUIVALENT CKT X AVO OSCILLATON _ Digital Troubleshooting AN HP VIDEOTAPE TRAINING PROGRAM Digital Troubleshooting a vid eotape series developed to train HP s own technicians is a course especially useful in showing how to approach real
41. ing the contents of a register ARCHITECTURE Any design or orderly arrangement perceived by man the architecture of the microprocessor Since the extant microprocessors vary considerably in design their architecture has become a bone of contention among specialists ASSEMBLER PROGRAM The Assembier Program translates man read able source statements mnemonics into machine understandable object code ASSEMBLY LANGUAGE A machine oriented language Normally the pro gram is written as a series of source statements using mnemonic symbols that suggest the definition of the instruction and is then translated into machine language ASYNCHRONOUS Operation of a switching network by a free running signal which signals successive instructions the completion of one in struction triggering the next There is no fixed time per cycle BAUD RATE A measure of data flow The number of signal elements per second based on the duration of the shortest element When each element carries one bit the Baud rate is numerically equal to bits pef second bps The Baud rates on UART data sheets are interchangeable with bps BCD Binary Coded Decimal Each decimal digit is binary coded into 4 bit words The decimal number 11 would become 0001 0001 in BCD Also known as the 8421 code BENCHMARK Originally a surveyors mark used as a reference point in surveys In connection with microprocessors the benchmark is a frequently used routine or program selected for the purpose
42. ing to further interrupt requests until cleared by execution of pro grammed instructions It may also be manipulated by specific mask bit instructions 1 O Input Output Package pins which are tied directly to the internal bus network to enable O to interface the microprocessor with the out side world J JUMP The Jump operation like the Branch operation is used to control the transter of operations from one point to a more distant point in the control program Jumps differ from Branching in not using the Relative Addressing mode L LABEL A label may correspond to a numerical value or a memory location in the programmable system The specific absolute address is not necessary since the intent of the label is a general destination Labels are a requisite for jump and branch instructions LIBRARY A collection of complete programs written for a particular computer minicomputer or microprocessor For example Second Order Differential Equation may be the name of a program in the Library of a particular computer this program will contain all the subroutines neces sary to perform the solution of second order differential equations written in machine language and using the instruction set of this machine LIFO Last in First Out buffer See Push Down Stack LOGIC A mathematical treatment of formal logic in which a system of symbols is used to represent quantities and relationships The symbols or logical functions are called AND OR N
43. istory lesson in Centigrade Celsius and Fahrenheit provided by Andr Rud HP Santa Clara Division Our present variety of scales dates back to the early 1700 s and the beginning of modern temperature measurement Then there were roughly as many scales as there were people who knew how to measure Among them were Gabriel Fahrenheit a Pole Anders Celsius a Swede and later on Lord Kelvin a Briton Fahrenheit who invented the mercury thermometer based zero on the lowest temperature he could obtain with a mixture of salt and ice which turned out to be 32 degrees Fahren heit below the freezing point of water As asecond reference point he picked the blood temperature of the human body and then divided the distance between these two points in 96 degrees Actually blood temperature is two or three degrees higher than Fahrenheit reckoned but inaccuracies in his original instrument caused this discrepancy Celsius meanwhile developed a scale defined by the freezing and boiling points of pure water at sea level Since he divided the space between these two points into 100 degrees the scale was called Centigrade from the Latin centum one hundred In 1927 the multination General Conference on Weights and Measures defined an international temperature scale which was in fact the Centi grade system In the meantime the Fahrenheit scale had come into com mon use in England and the United St
44. ith analog and digital IH Instrument Operation Nes circuits A Field Frequency Setting B Operating Routine PRESTUDY None WWW HPARCHIVE COM O rary e y N W aN AL H UDN NEED ANY SERVICE NOTES BENGI RIETS NDE Here s the latest listing of Service Notes available for Hewlett Packard products To obtain information for instruments you own remove the order form and mail it to the nearest HP distribution center 197A OSCILLOSCOPE CAMERA 197A 7 All serials Repair kits 745A AC CALIBRATOR 745A 10A Serials 1319A01251 through 1319A 01670 and 745A H18 s only serial numbers 319A01671 and above Triax counter output connector 745A 12A S Serials 00741 00101 through 1319A01250 Elimination of potential safety hazard Supersedes 745A 12 745A 13A Serials 00741 00101 through 1319A01670 and 745A H18 s only serial num bers 1319A01671 and above Installation of isolated BNC counter output modification kit HP part no 00745 89503 1332A X Y DISPLAY 1332A 5 All serials Improved reliability for the Z axis amplifier 1333A X Y DISPLAY 1333A 1 All serials Improved reliability for the Z axis amplifer 1335A X Y DISPLAY 1335A 2 All serials Improved storage circuitry reliability 1335A 3 All serials Improved reliability for the Z axis amplifier 1645A DIGITAL ERROR ANALYZER 1645A 6 All serials Preferred replacement for TTL decade counter 1645A 7 All serials Inverted clock ph
45. l Logic Circuits 30 minutes 12 Display Technologies 30 minutes 13 IC Manufacturing 11 minutes 14 Memories 25 minutes The videocassettes are available in the NTSC Standard only Formats other than 3 4 videocassette can be quoted on request The part number is 90420D which includes all tapes and study ma terial plus midterm and final exams exam solutions and certificates of completion See your local HP field en gineer for details 1700 Series Oscilloscopes FOCUS PROBLEMS Are you having problems adjusting the beam focus on your HP1700 series os cilloscope Service Notes for the 1710B 1712A 1720A and 1722A scopes describe the problem as being related to resistors A1R11 6 5 megohms and A15R13 13 megohms changing value Improved resistors from a different vendor are now being used same part number The new re sistors have a reddish brown body The original resistors had reddish brown gray or white bodies and are substantially smaller than the current resistors in use The Figure below shows the relative size of the new and old resistors is Reddish Brown All This Approximate Size oS AISAI1 6 SMR MP Part Number 0698 644 AI5RI3 13M HP Part Number 0698 6442 Figure 1 New Focus Resistor SAFETY RELATED SERVICE NOTES Service Notes from HP relating to personal safety and possible equip ment damage are of vital importance To make you more aware of these impo
46. ld be reset to zero every ten reference periods as shown in Fig ure 4 By cancelling the average phase advancement the average frequency from the divide by N block becomes an a t ___1 ___ 100 200 Reference Periods XN N 10 in frie sampile Time in nsec Figure 4 The Output of the Phase Detector Shown Here is a Sawtooth Riding on a dc Voltage WWW HPARCHIVE COM One Cycie Removed Every 10 Reterence nods LAF Average Frequency 1 00 MHe a m Figure 5 The Basic Block Diagram of a Modified N Step Loop With a Pulse Remover Added to Allow the VCO to Operate at a Fractional Frequency time the VCO advances one full cycle the pulse remover is actuated and the phase advancement is reset to its zero degree level The dc voltage level which the sawtooth is riding on can then be used as the tune voltage needed to phase lock the system The next step is to devise a method to trigger the pulse remover by determin ing when the VCO frequency has ad vanced one full cycle The fractional portion of the VCO contains the infor mation needed to accomplish this The fractional portion is stored in a register and added to a second register each reference period This second register called the phase register then contains a running total of the phase advance ment The contents of the phase regis ter are represented in the right hand column of Table 1 When the phase register reaches or exceeds unity the
47. main analysis Usually used in electronics in terms of voltage vs lime eg as displayed by an oscilloscope trace distinguished from the frequency domain where electrical analysis is usually voltage gain as a function of frequency DATA FIELD POINTER See Stack Pointer DEBUG As used in connection with microprocessor software debugging involves searching for and eliminating sources of error in programming routines Finding a bug in software routine is said to be as difficult as finding a needie in the proverbial haystack A single step tester is the suggested method so that each instruction operation can be checked individually D BUS See Data Bus DECREMENT A programming instruction which decreases the contents of a storage location See also increment and decrement DEDICATED To set apart for some special use A dedicated microproces sor is one thal has been specifically programmed for a single application such as weight measurement by scale traffic light control etc ROMs by their very nature Read Only are dedicated memories DIRECT ADDRESSING This is the standard addressing mode It is char acterized by an ability to reach any point in main storage directly Direct addressing is sometimes restricted to the first 256 bits in main storage DMA Direct Memory Access A method of gaining direct access to main storage to achieve data transfer without involving the CPU The manner in which CPU is disabled while DMA is in progr
48. mes during the lecture A familiarization with adjustment pro cedures is also included PREREQUISITES Basic knowledge of microwave measur COURSE CONTENTA ing techniques PRESTUDY April 1973 HP Journal describing LECTURE 5340A The Fundamentals of I Overall Block Diagram Electronic Frequency Counters II Numerical Examples of Frequency Measurements Application Note 172 I Input Phase Lock Loop Circuit Description IV Transfer Phase Lock Loop Circuit Description V Instrument Flow Diagram and Algorithmic State Machine VI Options 5062C CESIUM BEAM FREQUENCY STANDARD OCT 10 14 SANTA CLARA CA IV Cesium Beam Tube A Operation B Performance Verification V Circuit Alignment A Procedure B Circuit Alignment VI Troubleshooting A Procedures B Troubleshooting VII Subassembly Theory and Repair A Discussion of each Major Circuit Assembly COURSE CONTENT B Troubleshooting VII Options LECTURE A Battery I General Information By Gok A High Resolution Frequency Measurement C Troubleshooting B 5062C Specifications IX Summary A Review Il Block Diagram Theory and Control Sse ene ahr siren vg B Non Field Repairable Parts A Cesium Tube Characteristics Test Equi Reaui B RF Circuits side est Equipment Requirements C LF Circuits LAB D Front Panel Controls and Status Lamps The lecture will be given in a lab environment E Instrument Turn On PREREQUISITES Familiarity w
49. ns the address of data rather than the data itself INSTRUCTION SET Constitutes the total list of instructions which can be executed by a given microprocessor and is supplied to the user to provide the basic information necessary to assemble a program INTERFACE Indicates a common boundary between adjacent compon ents circuits or systems enabling the devices to yield and or acquire information trom one another In the face of common usage one must regrettully add that the words Buffer Handshake and Adapter are inter changeable with interface INTERRUPT An interrupt involves the suspension of the norma program ming routine of a microprocessor in order to handie a sudden request for service The importance of the interrupt capability of a microprocessor depends on the kind of applications to which it will be exposed When a number of peripheral devices interface the microprocessor one or several simultaneous interrupts may occur on a frequent basis Multiple interrupt requests require the processor to be able t accomplish the WWW HPARCHIVE COM MICROPROCESSOR BUZZ WORDS following to delay or prevent further interrupts to break into an inter rupt in order to handle a more urgent interrupt to establish a method of interrupt priorities and atter completion ot interrupt service to resume the interrupted program from the point where it was interrupted INTERRUPT MASK BIT The Interrupt Mask Bit prevents the CPU from respond
50. o a given operation To assist the human memory the binary numbered codes are assigned groups of letters or mnemonic sym bois that suggest the definition of the instruction LDA tor load accumu lator etc Source statements can be written in this symbolic language and then translated into machine language MICROPROGRAM This word pre dates the microprocessor and refers to computer instructions which do not reference the main memory storage It is a computer technique which performs subroutines by manipulating the basic computer hardware and is often referred to as computer within computer The word has not changed its basic meaning when used in connection with microprocessors but is not to be construed as native to microprocessors A series of instructions stored in a ROM any portion of which can implement a higher language program is labeled a micro program MICROINSTRUCTION See Microprogram MEMORY The part of a computer system into which information can be inserted and held for future use Storage and memory are interchangeable expressions Memories accept and hold binary numbers only Memory types are core disk drum and semiconductor MOS Metal Oxide Semiconductor The structure of an MOS Field Effect Transistor FET is metal over silicon oxide over silicon The metal electrode is the gate the silicon oxide is the insulator and carrier doped regions in the silicon substrate become the drain and source The result is a sandwich
51. of fractional N are ob vious greater frequency resolution wider frequency range and fewer loops DIVIDE BY N LOOP In order to more readily understand how a fractional N loop works one must first understand the more tradi tional phase lock loop with a divide by N element The fractional N loop is really a modified divide by N loop Figure 1 illustrates the basic concept involved in a phase lock loop The phase detector compares the Voltage Controlled Oscillator VCO output to the reference signal and produces a tune voltage proportional to the phase difference of these two inputs The tune voltage is cleaned up by passing it through a low pass filter to suppress noise and high frequency components The polarity of the tune voltage is such that it will pull the VCO frequency in a direction to phase track the reference frequency ee La Frequency Figure 1 Basic Phase Locked Loop Used to Produce Single Frequencies In the previous example the frequency of the VCO must match that of the ref erence For single frequency applica tions this is fine but to extend the use fulness of the loop a divide by N ele ment must be added as shown in Fig ure 2 The basic difference is that the VCO frequency is N times the refer ence frequency The modulus of the WWW HPARCHIVE COM MAY AUGUST 1977 Figure 2 A Phase Lock Loop With a Divide by N Element to Produce a Range of Frequencies in Steps Equal to Integ
52. of interrupt requests When several interrupts occur at one time the control program decides which one to service first PORT Device terminals which provide electrical access to a system or citcuit The point at which the 1 0 is in contact with the outside world PROGRAM A procedure for solving a problem and frequently reterred to as Software PROGRAM COUNTER One of the registers in the CPU which holds addresses necessary to step the machine through the program During interrupts the program counter saves the address of the instruction Branch ing also requires loading of the return address in the program counter PUSH DOWN STACK A register that receives information from the Pro gram Counter and stores the address locations of the instructions which have been pushed down during an interrupt This stack can be used for sub routining Its size determines the level of subroutine nesting one less than its size or 15 levels of subroutine nesting in a 16 word register When instructions are returned they are popped back on a last in tirst out LIFO basis P STACK See Push Down Stack RALU Register Arithmetic and Logic Unit Uniike the discrete ALU package which functions as an Arithmetic and Logic unit only the ALU in the microprocessor is equipped with a number of registers RAM Random Access Memory Random in the sense of providing access to any storage location point in the memory immediately by means ot vertical and horizontal co ordin
53. of the phase detector This essentially eliminates the saw tooth portion of the output of the phase detector and when filtered produces a clean dc tune voltage for the VCO Figure 8 Highly Simplified Diagram of a Fractional N Phase Lock Loop This ends a simplified explanation of the concepts involved in a fraction N loop Actual implementation is more complex For example to convert the staircase output of the phase register into a smooth sawtooth requires cur rent sources and an integrator A sam ple and hold circuit is used to produce a transient free dc tune voltage A tune current is needed to allow the loop to relock after a large change in VCO fre quency Despite the additional cir cuitry the basic principle given in this article will still hold true O COUNTRIES AND THEIR VOLTAGES Following is a complete and up to date guide to foreign voltages In general all references to 110V apply to the range 100V to 160V References to 220V apply to the range from 200V to 260V Where 110 220V is indicated voltage varies within country depending on lo cation Aden 220V Curacao 110V Afghanistan 220V Ciba s IOV Algeria 110 220V Cyprus 220V Angola v Czechoslovakia 110 220V Anguilla 220V Dahomey 220V Antigua 110 220V Denmark 220V tArgentina _ _ 220V Dominica Aruba 110V Dominican Rep 110 220V Australia 220V Ecuador 110 220V Austria 220V Egypt 110 220V Azores 110 220V
54. ogrammabie in the field with the aid of programmer equipment Program data stored in ROMs are often called firmware because they cannot be altered However another type of P ROM is now on the market called EPROM which is erasible by ultra violet irradiation and electrically reprogrammabie WWW HPARCHIVE COM SCRATCHPAD This term is applied to information which the Processing unit stores or holds temporarily It is a memory containing subtotals for various unknowns which are needed for final results SEQUENTIAL LOGIC A circuit arrangement in which the output state is determined by the previous state of the input See also Combination Logic SOFTWARE What sheet music is to the piano software is to the com puter Looked at from a practical point of view one might say that software is the computer s instruction manual The name software was obviously chosen to contrast with the formidable hardware which confronted the first programmers Software is the language used by a programmer to communi cate with the computer Since the only language spoken by a computer is mathematical the programmer must convert his verbal instructions into numbers In the case of microprocessors which vary from maker to maker software libranes are assembled by the manufacturer for the benefit of the user SOURCE STATEMENT A program written in other than machine lan gauge usually in three letter mnemonic symbols that suggest the defin ition of the instruction
55. problems in real equipment These videocassettes provide e Practical demonstrations Flexibility of use for classroom or in dividual study Latest in digital troubleshooting tools Most recent logic symbology ANSI Y32 14 IEEE 91 1973 Useful troubleshooting tips This course was designed developed and made for technicians It is an ap propriate bridge from transistors to digi tal electronics or a digital refresher course Equivalent in coverage to a col lege term of 13 weeks Digital Troub leshooting is presented in color on 14 videocassettes having a total running time of 5 hours and 31 minutes The lab demonstrations shown in video are from the workbook included with the series Also included is a 180 page text and a study guide WWW HPARCHIVE COM ee There is ample use of reinforcement in the presentation and in the self scoring quizzes at the end of most of the mod ules Individual tapes are 1 Introduction To Digital Electronics 12 minutes 2 Binary Nature of Digital Circuits 18 minutes 3 Basics of Transistors and IC s 18 minutes 4 Logic Gates and Symbols 25 minutes 5 Introduction To Digital IC Families 29 minutes 6 Modern Digital IC Families 27 minutes 7 Simple Troubleshooting Techniques 18 minutes SAFETY SERVICE NOTES 8 Troubleshooting Digital IC s 27 minutes 9 Flip Flops 31 minutes 10 Counters and Shift Registers 30 minutes 11 Combinationa
56. r means ol processing data because of the shortened code ACCUMULATOR One or more registers associated with the ALU which temporarily store sums and other arithmetical and logical results of the ALU ACIA Asynchrous Communications interface Adapter A Motor ola device which interfaces the microprocessor s bus organized system with incoming serial synchronous communication information The parallel data of the multi bus system is serially transmitted by the asynchronous data terminal The ACIA interfaces directly with low speed Modems to enable microprocessor Communication over telephone lines ADAPTER A device used to effect operative Capability between different parts of one or more systems or subsystems ADDRESSING MODES An address is a coded instruction designating the location of data or program segments in storage The address may refer lo storage in registers or memories or both The address code itself may be stored so that a location may contain the address of data rather than the data itself This form of addressing is common in micropro cessors Addressing modes vary considerably because of efforts to reduce program execution time ALU Arithmetic and Logic Unit The ALU is one of the three essential components of a microprocessor the other two being the registers and the contro block The ALU performs various forms of addition and subtraction the logic mode performs such logic operations as ANDing the contents of two registers or mask
57. r brother took 10 rubles the older brother took another 10 rubles then the younger brother took another 10 rubles They continued dividing the money this way until the younger brother whose turn it was found there were fewer than 10 rubles left so he took what remained To make the division just the older brother gave the younger brother his penknife which was valued at 4 rubles How many sheep were in the flock Hint There are multiple answers so use the first one that satisfies the above conditions WWW HPARCHIVE COM EQUATIONS CORRECTED Dear Editor Gee wheeze before solving your Equations that Changed The World please be warned that this letter is Belng Typed by the SAme typesetter who type et the Readers Corner Sept Dec 1976 i sue That 1 1 2 is true only on base 10 and it would fit 4 but only if the tallying is done by non computers So a corresponds to 4 and b goes with 5 while c will pick on 1 Now d will make Napier and others cringe because the exponent of e contains a mysterious one Anyway tell your type etter and proofreader that ell enn is the proper notation for logarithms NOW 6 will go with d won t it Pythagoras will approve of e and 2 as is Bravo f joins 7 though not as standard notation Tsilkovskii s formula g and 3 can also stand a bit of clean up while in g again the mysterious one
58. ral Multiples of the Reference Frequency divide by N block can be stepped to produce frequencies that are integral multiples of the reference The VCO can now produce a range of discrete frequencies all phase locked to the reference FRACTIONAL N LOOP OPEN LOOP CONDITION A fractional N loop is simply a modified divide by N loop The fractional N loop is capable of operating at frequencies which are not integral multiples of the reference signal In fact the fractional N loop can be made to operate at any frequency greater than the reference frequency up to the upper limit of the IN THIS ISSUE FREQUENCY SYNTHESIS DIGITAL TROUBLESHOOTING VIDEO TAPE SERVICE TRAINING SEMINARS TROUBLESHOOTING DC REGULATED POWER SUPPLIES NEW SERVICE NOTES VCO As mentioned previously the divide by N loop in the 3335A Synthesizer Level Generator produces 39 MHz to 79 MHz in 1 MHz steps using a 1 MHz reference and the fractional N loop in the 3335A produces from 1 MHz to 1 999999999 MHz in 0 001 Hz steps using a 100 kHz refer ence signal The best place to begin this explana tion is to assume an open loop config uration for a normal divide by N loop see Figure 3 For this example as sume that the reference frequency is Figure 3 The Basic Block Diagram of and N Step Loop in an Open Loop Condition 100 kHz and that the divide by N number is 10 Also assume that the VCO frequency is 1 01 MHz This means t
59. rtant notes HP has recently modified the Safety Service Note format The note is now printed on paper with a red border and a S suffix has been added to the note s number In order to make you immediately aware of any potential safety problems we are highlighting safety related Service Notes here with a brief description of each problem Also in order to draw your attention to safety related Service Notes on the Service Note order form at the rear of Bench Briefs each appropriate num ber is highlighted by being printed in color 745AC CALIBRATOR HP 745A Calibrators with serials 00741 00101 thru 1319A01250 have the COUNTER OUTPUT BNC connec tor shell connected to the output LO SENSE terminal When the 745A output is floated above ground this BNC connector will have the same potential as the LO SENSE and LO WWW HPARCHIVE COM OUTPUT terminals Use the following procedure to test your instrument for this condition 1 Turn the power switch off discon nect all power cords and signal cables Disconnect the ground strap between LO OUTPUT and chassis ground 2 Set an ohmmeter to the 1 kilohm range and connect one end to the LO SENSE terminal 3 Connect the other ohmmeter lead to the outer shell of the COUNTER OUTPUT jack on the rear panel 4 The ohmmeter should indicate infinity If not order the following parts and Service Note to modify the 745A to conform to current safety standards Service Not
60. s WWW HPARCHIVE COM READERS CORNER NEED HELP ON AN INSTRUMENT Hewlett Packard is in the process of installing toll free direct lines into our larger Instrument Service Centers located throughout the United States This non transferrable line bypasses receptionists allowing you to cut through delays in getting needed service information You will be promptly answered by competent ser vice representatives ready to provide instrument maintenance pricing parts and troubleshooting information and other technical support assistance Not all areas of the country are on the toll free lines yet and the telephone numbers will vary from area to area So check with your local Hewlett Packard Sales and Service Office for toll free status in your area Customers with analytical medical computer and calculator products will continue to be best served by contact ing their nearest HP office also We are prepared to help solve your instrument support problems simply call PERMISSION FOR REPRINT Editor Bench Briefs In your July August 1976 issue you included a one page article Shock Hazard Considera tions As Assistant Editor of the RARA RAG monthly magazine of the Rochester Amateur Radio Association would like to include that article in a future issue Our club has lots of newcomers this year have a feeling it will enlighten both oldsters and newcomers Please reply whether you
61. serials Field effect transistor lead configuration 5045A DIGITAL IC TESTER 5045A 1 All serials Textool zip dip socket replacement 5150A THERMAL PRINTER OPTION 002 BCD INTERFACE 5150A 1 All serials Modification to improve immunity to spurious print signals 5150A THERMAL PRINTER 5150A 2 All serials Repair of and ad justments to the print head assembly 5304A TIMER COUNTER 5304A 1 Serials 1704A03241 and below Serials 1632U01490 and below Modification to improve performance 5328A UNIVERSAL COUNTER 532BA 3 Modification to prevent annunciator lighting problem 5328A 4 Serials 1704A02560 and below Spurious oscillation in arm lines 5340A MICROWAVE FREQUENCY COUNTER 5340A 8 All serials Using a logic state analyzer for 5340A ASM troubleshooting 5340A 9 Serials 1644404200 and below Line fuse change for improved transformer protec tion 5340A 10 Serials 1644A04300 and above Thermal switch change 7200A 7201A 7202A GRAPHIC PLOTTERS 7200A 17A 7201A 7A 7202A 17A 9125A B 5SA Serials 1620A and below New chart hold autogrip module 8552A SPECTRUM ANALYZER IF SECTION 8552A 12 Serials 1650A and below Modifica tion to reduce fuse blowing in IF section when switching the log linear mode switch 8552B SPECTRUM ANALYZER IF SECTION 8552B 12 Serial 1650A and below Modifica tion to reduce fuse blowing in IF section when switching the log linear mode switch 8554B SPECTRUM ANALYZER RF SECTION 8554B
62. st equal Vz Therefore Vo Vz Re Rx Re or Im Vz Rm Rx Re The values of Vz and Rm shown yield Rx Re Im if Im is the meter reading in mil liamperes For an Re of 100 kilohms the 1 ma meter deflects full scale when Rx is 100 kilohms Similarly full scale can be made to indicate 10 kilohms or 1 kilohm by selecting these values for Re A range switch can be included in the circuit to set these values The current through the unknown resistor Ix is independent of the value of Rx The equality of the op amp input voltages makes Vz equal to IxRe So lx V2 Re The meter has automatic zeroing because if the measuring leads are short circuited Vo rises to exactly 3 v sending no current into the meter No calibration is necessary because the meter deflection has direct corre spondence to the value of resistance being measured WWW HPARCHIVE COM The germanium diode limits the volt age across the meter and thus protects it from over current when the measuring leads are left open Ve moot a Milliamperes indicate resistance The meter reading in mA is the value of the ratio Rx Re so full scale meter deflection indicates an Rx of 100 kilohms An open circuit pins the meter but does no dam age because the germanium diode clamps the meter voltage Since a short circuit produces no deflection the circuit is self zeroing Improved Power Switch ATTENTION INSTRUMENTATIO
63. tates in an effort to bring our training facilities closer to your area For registra tion please use the form on page 15 of Bench Briefs or contact your Hewlett Packard Sales and Service Office Hewlett Packard continually offers train ing to customers on a worldwide basis to help keep service skills current with HP s extensive product line Seminars are pro vided throughout Europe and the United CUSTOMER SERVICE SEMINARS COURSE CONTENT LECTURE l Introduction 8640 AM FM SIGNAL GENERATOR 8660 SYNTHESIZED SIGNAL GENERATOR Il Features and Model Options 435 436 POWER METERS 8480 SENSOR AND 11683A CALIBRATOR III Front Panel Features AUG 29 SEPT 2 PALO ALTO CA A Video Tape B Demonstration IV Theory A Block Diagram B Assembly Locations C Schematic LAB If Adjustments Il Performance Tests Ill Troubleshooting PREREQUISITES Basic knowledge of digital logic cir cuits and general knowledge of elec tronics including operational ampli fiers and phase lock circuits PRESTUDY Review digital logic and block dia gram information in 8640 8660 and 435 436 manuals Read pages 1 48 in Signal Generator Seminar textbook View video tape 90030__566 Optional WWW HPARCHIVE COM CUSTOMER SERVICE SEMINARS 5340A MICROWAVE FREQUENCY vo LAB COUNTER i vA The lecture is given in a lab environment Attendees make SEPT 1 2 PARAMUS NJ AN X voltage and waveshape measurements at different ti
64. we ne BRIEES SERVICE INFORMATION FROM HEWLETT PACKARD FRACTIONAL N SIMPLIFIES FREQUENCY SYNTHESIS by Kenneth Jessen HP Loveland Division INTRODUCTION Hewlett Packard is introducing several new instruments that use a new fre quency synthesis technique known as fractional N This new technique over comes many of the limitations of the traditional divide by N loop Any given divide by N loop can only produce fre quencies which are integral multiples of the reference frequency The 3330B Automatic Synthesizer for example uses four divide by N loops of different frequency ranges to produce an overall range from 0 1 Hz to 13 000 999 9 Hz The first second and third digits of the output frequency are controlled by the first divide by N loop The fourth and fifth digits are controlled by the second divide by N loop the sixth and seventh digits are controlled by the third loop and the remaining two digits by the fourth loop Summation loops are also required to sum the outputs of the divide by N loops but they are ignored to simplify this discussion The new HP3335A Synthesizer Level Generator can produce frequencies from 200 00 Hz to 80 099 999 999 Hz using only two loops One loop is a common divide by N loop producing 39 MHz to 79 MHz in 1 MHz steps The second loop and topic of this article is a fractional N loop able to generate frequencies from 1 MHz to 1 999999999 MHz in 0 001 Hz steps The advantages

FRACTIONAL N SIMPLIFIES FREQUENCY SYNTHESIS

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