National Instruments GPIB
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1. National Instruments Corporation Programming the GPIB COM Description Parity Enable Bit If this bit is set the INS8250 will generate and check parity according to the values of the STP and EVEN bits bits 4 and 5 If this bit is clear the INS8250 will not generate or check parity bits This bit is ignored by the GPIB COM Stop Bit Control Bit This bit controls the number of stop bits sent and verified by the INS8250 If this bit is set two stop bits will be used If this bit is clear one stop bit will be used This bit is ignored by the GPIB COM Word Length Select Bits These two bits set the length of the words sent or received according to Table 5 3 Table 5 3 Word Length Select Bits These bits have no meaning on the GPIB and are ignored by the GPIB COM circuitry 5 9 GPIB COM User Manual Programming the GPIB COM Section Five Modem Control Register Offset from Base I O Address 4 Register Address XFC 7 6 5 4 3 2 1 0 The Modem Control Register is a read write register that controls RS 232 output lines for communication with a modem or modem emulator The function of each bit in this register is explained below Bit Mnemonic Description 7 Sr w 0 Reserved Bits 7 through 5 These bits always read as 0 Ar w LOOP Loopback Diagnostic Test Bit When set this bit internally connects the outputs of the INS8250 back to the inputs to allow the chip to be tested by writing data to itself and reading it b2. Bit Mnemonic Description 7 Or D 7 0 Data Bits 7 through 0 National Instruments Corporation 5 3 GPIB COM User Manual Programming the GPIB COM Section Five Divisor Latch Least Significant Byte LSB Register Offset from Base I O Address 0 Register Address XF8 DLAB bit in Line Control Register 1 7 6 5 4 3 2 1 0 Bit Mnemonic Description 7 Or w DL 7 0 Data Bits 7 through 0 Divisor Latch Most Significant Byte MSB Register Offset from Base I O Address 1 Register Address XF9 DLAB bit in Line Control Register 1 7 6 5 4 3 2 1 0 puis o pus puo mu Duo RAN The value stored in these two registers is used to determine the baud rate for serial communica tions The 16 bit number formed by the Divisor Latch LSB and MSB is divided into a 1 8432 MHz clock to produce the baud rate The Divisor Latch Registers are ignored by the GPIB COM circuitry however they are available on the GPIB COM and can be written to and read by software Bit Mnemonic Description 7 Or w DL 15 8 Data Bits 15 through 8 GPIB COM User Manual 5 4 National Instruments Corporation Section Five Programming the GPIB COM Interrupt Enable Register Offset from Base I O Address 1 Register Address XF9 DLAB bit in Line Control Register 0 7 6 5 4 3 2 1 0 The Interrupt Enable Register 1s a read write register that allows the programmer to selectively enable or disable each of the four possible types of interrupts gene
3. which is used to place devices in remote or local program mode SRQ service request Any device can drive the SRQ line to asynchronously request service from the Active Controller EOI end or identify The EOI line has two purposes The Talker uses the EOI line to mark the end of a message string The Active Controller uses the EOI line to tell devices to identify their responses in a parallel poll GPIB COM User Manual C 4 National Instruments Corporation Appendix C Operation of the GPIB Physical and Electrical Characteristics Devices are usually connected with a cable assembly consisting of a shielded 24 conductor cable with both a plug and receptacle at each end This design enables devices to be connected in either a linear or a star configuration or a combination of the two See Figures C 2 and C 3 Figure C 2 Linear Configuration of the GPIB Devices National Instruments Corporation C 5 GPIB COM User Manual Operation of the GPIB Appendix C Figure C 3 Star Configuration of GPIB Devices The standard connector is the Amphenol or Cinch Series 57 MICRORIBBON or AMP CHAMP type An adapter cable using non standard cable and or connector is used for special interconnect applications The GPIB uses negative logic with standard TTL logic levels When DAV is true for example it is a TTL low level 0 8 V and when DAV is false it is a TTL high level 2 2 0 V GPIB COM User Manual C 6 National Instrument
4. 045 37 MLAS 06 006 6 ACK 26 046 38 amp MLA6 07 007 7 BEL 27 047 39 MLA7 08 010 8 BS GET 28 050 40 MLAS8 09 011 9 HT TCT 20 051 41 MLA9 0A 012 10 LF 2A 052 42 ti MLA10 OB 013 11 VT 2B 053 43 MLA11 OC 014 12 FF 2C 054 44 MLA12 OD 015 13 CR 2D 055 45 MLAI13 OE 016 14 SO 2E 056 46 MLA14 OF 017 15 SI 2F 057 47 MLAI5 10 020 16 DLE 30 060 48 0 MLA16 11 021 17 DCI LLO 31 061 49 1 MLA17 12 022 18 DC2 32 062 50 2 MLAI8 13 023 19 DC3 33 063 51 3 MLA19 14 024 20 DC4 DCL 34 064 52 4 MLA20 15 025 21 NAK PPU 35 065 53 5 MLA2I 16 026 22 SYN 36 066 54 6 MLA22 17 027 23 ETB 37 067 55 7 MLA23 18 030 24 CAN SPE 38 070 56 8 MLA24 19 031 25 EM SPD 39 071 57 9 MLA25 1A 032 26 SUB 3A 072 58 MLA26 1B 033 27 ESC 3B 073 59 MLA27 IC 034 28 FS 3C 074 60 MLA28 ID 035 29 GS 3D 075 61 MLA29 1E 036 30 RS 3E 076 62 gt MLA30 1F 037 31 US 3F 077 63 UNL Message Definitions DCL Device Clear MSA _ My Secondary Address GET Group Execute Trigger MTA My Talk Address GTL Go To Local PPC Parallel Poll Configure LLO Local Lockout PPD Parallel Poll Disable MLA My Listen Address GPIB COM User Manual B 2 National Instruments Corporation Appendix B PPE PPU SDC SPD Multiline Interface Command Messages Multiline Interface Messages Oct Dec ASCII 100 64 101 65 A 102 66 B 103 67 C 104 68 D 105 69 E 106 70 F 107 71 G 110 72 H 111 73 I 112 74 J 113 75 K 114 76 L 115 77 M 116 78 N 117 79 O 120 80 P 121 81 Q 122 82
5. R 123 83 S 124 84 T 125 85 U 126 86 V 127 87 W 130 88 X 131 89 M 132 90 Z 133 91 134 92 135 93 136 94 A 137 95 _ Parallel Poll Enable Parallel Poll Unconfigure Selected Device Clear Serial Poll Disable National Instruments Corporation Msg MTAO MTAI MTA2 MTA3 MTA4 MTAS MTA6 MTA7 MTA8 MTA9 MTA10 MTAII MTA12 MTA13 MTA14 MTA15 MTAI6 MTAI17 MTAI18 MTAI9 MTA20 MTA21 MTA22 MTA23 MTA24 MTA25 MTA26 MTA27 MTA28 MTA29 MTA30 UNT B 3 Hex Oct 60 140 61 141 62 142 63 143 64 144 65 145 66 146 67 147 68 150 69 151 6A 152 6B 153 6C 154 6D 155 6E 156 6F 157 70 160 71 161 72 162 73 163 74 164 75 165 76 166 11 167 78 170 79 171 7A 172 7B 173 7C 174 7D 175 7E 176 7F 177 SPE TCT UNL UNT Dec ASCII Msg 96 MSAO PPE 97 a MSAI PPE 98 b MSA2 PPE 99 c MSA3 PPE 100 d MSAA PPE 101 e MSAS PPE 102 f MSA6 PPE 103 g MSA7 PPE 104 h MSAS PPE 105 1 MSA9 PPE 106 j MSA10 PPE 107 k MSA11 PPE 108 l MSA12 PPE 109 m MSA13 PPE 110 n MSA14 PPE 111 o MSA15 PPE 112 p MSA16 PPD 113 q MSA17 PPD 114 r MSA18 PPD 115 S MSA19 PPD 116 t MSA20 PPD 117 u MSA21 PPD 118 V MSA22 PPD 119 W MSA23 PPD 120 x MSA24 PPD 121 y MSA25 PPD 122 Z MSA26 PPD 123 MSA27 PPD 124 MSA28 PPD 125 MSA29 PPD 126 MSA30 PPD 127 DEL Serial Poll Enable Take Control Unlisten Untalk GPIB COM User Manual Appendix C Operation of the GPIB History of the GPIB The GPIB is a link bus or int
6. interrupt level for each serial port Table 2 1 IBM PC Serial Port Adapters Base I O Address hex Interrupt Level Switch and Jumper Settings Table 2 2 shows the factory settings and optional configurations for the switches and jumpers on the GPIB COM Table 2 2 Factory Default Settings and Optional Configurations Base I O Address 2F8 3E8 2E8 If you need to change the factory settings continue on If you do not need to change the factory settings skip to Installation later in this section Base I O Address and Interrupt Selection The base I O address and interrupt line used by the GPIB COM are determined by the jumpers located at positions W2 and W5 The jumpers are set at the factory for base I O address 3F8 hex and interrupt level 4 National Instruments Corporation 2 3 GPIB COM User Manual Configuration and Installation Section Two Figure 2 2 shows the four possible combinations of jumper settings w5 w5 3X8 2X8 3X8 2X8 IRQ4 IRQ3 IRQ4 IRQ3 N N a COM1 Jumpers Set to Base I O Address b COM2 Jumpers Set to Base I O Address 3F8 hex and Interrupt Level 4 Default 2F8 hex and Interrupt Level 3 w5 w5 N N c COM3 Jumpers Set to Base I O Address d COM4 Jumpers Set to Base I O Addres 3E8 hex Interrupts Not Used 2E8 hex Interrupts Not Used XE8 Figure 2 2 Possible Settings for GPIB COM Jumpers Talk Listen Modes If you are using your GPIB COM with a listen only pri
7. the SRQ line through the Parity Error Bit PE in the Line Status Register When the switch is ON the PE bit reflects the status of the SRQ line When the switch is OFF the PE bit is always clear The GPIB COM factory default switch configuration is for device listen address 5 REN not asserted IFC enabled and SRQ enabled Figure 2 4 shows the factory default switch settings for the GPIB COM Key Bl side you must press down for default setting Off 1 On This side down for logic Figure 2 4 Switch Setting for REN OFF IFC ON SRQ ON and Listen Address 5 Default Setting National Instruments Corporation 2 5 GPIB COM User Manual Configuration and Installation Section Two Figure 2 5 shows the switch configuration needed when using a device with listen address 10 hex The listen address varies with each device so check the listen address of your device and set these five bits accordingly Key BE side you must press down for Listen Address 10 Off 1 On 0 ES used for setting REN ON IFC ON and SRQ ON This side down for logic 1 U13 This side down for logic 0 c S 9 L TIT 8 Figure 2 5 Listen Address Setting for Listen Address 10 Hex GPIB COM User Manual 2 6 National Instruments Corporation Section Two Configuration and Installation Figure 2 6 shows the switch configuration for REN asserted IFC disabled and SRQ disabled Key EM side you must pres
8. B COM User Manual 3 4 National Instruments Corporation Section Four Running Diagnostic Tests The GPIB COM Test Commands The GPIB COM Diagnostic Tests can be used to verify the configuration of the GPIB COM and its connection to a GPIB printer or plotter To run a GPIB COM diagnostic test connect a printer or plotter to the GPIB and run the program com exe from the GPIB COM diagnostic test diskette The following message will appear on the screen NATIONAL INSTRUMENTS GPIB COM DIAGNOSTIC TESTS This program assumes the GPIB COM is configured at base address 3F8 COM1 If you reconfigured your GPIB COM you must change the address that this program uses To do this enter command c from the menu Enter one of the following commands 1 printer test 2 plotter test c change COM configuration q quit A short explanation of each command is given in the following paragraphs 1 printer test Select this test to verify the configuration of the GPIB COM when connecting it to a GPIB ASCII printer This test will send characters to the printer Entering this command returns the prompt Starting printer test Press any key to stop printing National Instruments Corporation 4 1 GPIB COM User Manual Running Diagnostic Tests Section Four The printer should begin printing a string of characters To stop the test press any key The following message then appears P
9. GPIB COM User Manual June 1990 Edition Part Number 320197 01 O Copyright 1989 1991 National Instruments Corporation All Rights Reserved National Instruments Corporation 6504 Bridge Point Parkway Austin TX 78730 5039 512 794 0100 800 IEEE 488 toll free U S and Canada Technical support fax 512 794 5678 Limited Warranty The GPIB COM is warranted against defects in materials and workmanship for a period of two years from date of shipment National Instruments will repair or replace equipment which proves to be defective during the warranty period This warranty includes parts and labor A Return Material Authorization RMA number must be obtained from National Instruments before any equipment is returned for repair Faults caused by misuse are not covered under the warranty During the warranty period the owner may return failed parts to National Instruments for repair National Instruments will pay the shipping costs of returning the part to the owner All items returned to National Instruments for repair must be clearly marked on the outside of the package with an RMA number No other warranty is expressed or implied National Instruments shall not be liable for consequential damages Contact National Instruments for more information Important Notice The material in this manual is subject to change without notice National Instruments assumes no responsibility for errors which may appear in this manual National Ins
10. National Instruments Corporation 1 1 GPIB COM User Manual Introduction Section One Figure 1 1 shows the GPIB COM interface board E ed ve CRREL 2 E cT l5 TTS done o COPYRIGHT 1999 TONY oe 2 Figure 1 1 GPIB COM Board What Your Kit Should Contain Your kit should contain the following components GPIB COM interface board 180750 01 GPIB COM User Manual 320197 01 GPIB COM Diagnostic Test Diskette 420212 45 Note The GPIB COM Diagnostic Test Diskette contains the com exe diagnostic test that is described in Section Four Running Diagnostic Tests Make sure each of these items is in your kit If any item is missing contact National Instruments GPIB COM User Manual 1 2 National Instruments Corporation Section One Introduction Optional Equipment Double Shielded Cables GPIB Type X2 Cable 1 m 763061 01 GPIB Type X2 Cable 2 m 763061 02 GPIB Type X2 Cable 4 m 763061 03 In order to meet FCC emission limits for a Class B device you must use a shielded GPIB cable Operating this equipment with a non shielded cable may cause interference to radio and television reception in residential areas National Instruments Corporation 1 3 GPIB COM User Manual Section Two Configuration and Installation This section contains information on how to configure and install the GPIB COM into your system Configuration Figure 2 1 shows the locations of the GPIB COM confi
11. Programming the Serial Adapters e wie et aeui ve Meet ne o Seed 5 16 Polling Method es nn a RER DES nm eben un 5 16 Interrupt Driven MeN OM 4 6oetusetestotGa de dd SR EUER MIS REN rS 5 16 The CrPIB C ONT Controller Tui Ome aeque OUS SOPORE vd te 5 17 Appendix A SPECHICALIONS s acne een ea tu Ru ne E SUAE Im M ERO A DESEE Ef A 1 Appendix B Multiline Interface Command Messages B 1 Appendix C Operation of the GPIDB a Habere bein ett sah Teed etal Sree C 1 History of the GPIB iia uento ERO n ERE I tuile eese eis pie pe n Ee C 1 Typesof Messages ne ne Se ne mnt ne nt aE EREN E send dettes bes C 1 Talkers Listeners and Controllers siens C 1 System Controller and Active Controller C 2 GPP TES STEDOTS root eue MOI e aed ena usamos oui C 2 D EP AE LRO Eo PP Ml c Dc C 3 Handshake Deseo cede ecce eate isses eee ie d e ti Melo ua C 3 NRED not ready for data odii decur eet nena t queso dod C 3 NDAC DEO Accepted senecta oett ee Mises need ie eee C 3 DAV data valid ut ee T ee ee re ere Ee AU EVER C 4 Interface Management LINES sirier tn rbv Heat roe n t tons C 4 A EN Cattenti On 33 93 oe ER oS dette treten C 4 THE anterface cleaty i naine han ert ee e eT e De ERE el C 4 REN remote enable 5 se 5 1 reve eet E DERE DIE C 4 SRO service TEQUESE Gastos idus p Est ete Rene UN PRENNE Dax ea REPRE ete AUN C 4 EOL end or identify uu edicit eere IHREN ISI H URN EEX ASSETS EN a C 4 Physical and Electrical Characteristics nin
12. ack for verification This bit is ignored by the GPIB COM circuitry 3r w OUT2 Auxiliary Output 2 Bit The OUT2 serial port output is the inverse of this bit All interrupts from the serial adapter are disabled when this bit is cleared When this bit is cleared interrupts are disabled on the GPIB COM 2r w OUTI Auxiliary Output 1 Bit The OUTI serial port output is the inverse of this bit This bit is ignored by the GPIB COM circuitry 1r w RTS Request to Send Bit The RTS serial port output is the inverse of this bit When this bit is set it indicates that the Controller is ready to send data On the GPIB COM this bit is used along with the DTR bit to control the CTS bit of the Modem Status Register GPIB COM User Manual 5 10 National Instruments Corporation Section Five Bit Mnemonic Or w DTR National Instruments Corporation Programming the GPIB COM Description Data Terminal Ready Bit The DTR serial port output is the inverse of this bit This bit is set when the Controller is ready to communicate On the GPIB COM this bit is used along with the RTS bit to control the CTS bit of the Modem Status Register 5 11 GPIB COM User Manual Programming the GPIB COM Section Five Line Status Register Offset from Base I O Address 5 Register Address XFD 7 6 9 4 3 2 1 0 R The Line Status Register provides information about the status of the data transfer On the GPIB COM this register is implemented a
13. acter This bit functions identically on the GPIB COM and the INS8250 Received Data Available Interrupt Enable Bit This bit enables a received data available interrupt when set The received data available interrupt occurs when a character is received from the serial input and stored in the Receive Buffer Register This bit functions identically on the GPIB COM and the INS8250 5 6 National Instruments Corporation Section Five Programming the GPIB COM Interrupt Identification Register Offset from Base I O Address 2 Register Address XFA 7 6 5 4 3 2 1 0 R REZ EARS ESE XE XE X The Interrupt Identification Register is a read only register which tells you when an interrupt is pending and if so what kind of interrupt it is This register functions identically on the GPIB COM and the INS8250 Bit Mnemonic Description 7 3r 0 Reserved Bits 7 through 3 These bits always read as 0 2 lr ID 1 0 Identify Interrupt Register Bits These two bits identify the interrupt that is pending If more than one interrupt is pending only the one with the highest priority is identified The types and priorities are given in Table 5 2 Table 5 2 Interrupt Types and Priorities 0 0 Receiver Line Status 0 1 Received Data Available 1 0 Transmitter Holding Register Empty 1 1 Modem Status Or INT Interrupt Pending Bit This bit is clear if an interrupt is pending If set no interrupt is pending National Instruments Corpor
14. ation 5 7 GPIB COM User Manual Programming the GPIB COM Section Five Line Control Register Offset from Base I O Address 3 Register Address XFB 7 6 3 4 3 2 1 0 The Line Control Register is a read write register that allows the programmer to set the RS 232 parameters for the INS8250 The function of each bit in this register is explained below Bit Mnemonic Description Tr w DLAB Divisor Latch Access Bit This bit controls which registers will respond to I O addresses XF8 and XF9 This bit is set to access the Divisor Latch LSB and MSB and cleared to access the Transmitter Holding Register the Receive Buffer Register and the Interrupt Enable Register This bit functions identically on the GPIB COM and the INS8250 6r w SBRK Set Break Control Bit When set this bit causes the SOUT line of the serial cable to be forced to a logical 0 state This bit is ignored by the GPIB COM 5r w STP Stick Parity Bit When this bit is set the parity bit transmitted and detected will be the inverse of the EVEN bit bit 4 regardless of the number of l s in the data word This bit is ignored by the GPIB COM Ar w EVEN Even Parity Select Bit If this bit is set even parity will be generated and checked If this bit is clear odd parity will be generated and checked This bit is ignored by the GPIB COM GPIB COM User Manual 5 8 National Instruments Corporation Section Five Bit Mnemonic 3r w PEN 2r w STB 1 Or w WL 1 0
15. be written to the Transmitter Holding Register and polling continues Interrupt Driven Method In the interrupt driven mode of operation the desired interrupts are enabled through the OUT2 bit and the Interrupt Enable Register An interrupt handler is installed to respond when an interrupt occurs Software processes can perform other tasks until an interrupt is received When an interrupt occurs the handler reads the Interrupt Identification Register to determine the type of interrupt and takes appropriate action such as reading the Receive Buffer Register in the case of a received data available interrupt writing to the Transmitter Holding Register if it was a THRE interrupt or printing an error message in the case of a line status interrupt GPIB COM User Manual 5 16 National Instruments Corporation Section Five Programming the GPIB COM The GPIB COM Controller Function Because most serial port applications involve communication with only one serial line the GPIB COM imposes some restrictions on the GPIB in order to be compatible with existing serial port software The GPIB COM must be System Controller of the GPIB and will not work with other Controllers The behavior of the GPIB COM depends on the setting of the talk only jumper If the jumper is set to talk only the GPIB COM assumes that there is a listen only device connected to the GPIB When a byte is written into the Transmitter Holding Register the GPIB COM sets the THRE b
16. e Registers The main component of an IBM PC compatible serial adapter is an INS8250A Asynchronous Communications chip or its equivalent which handles RS 232 communication The INS8250A compatible registers on the GPIB COM emulate the serial adapter registers so that the GPIB COM will operate transparently with any serial port driver GPIB Acceptor and Source Handshaking This circuitry converts PC serial port handshaking into GPIB handshaking This process is completely software transparent Mode Control Logic This circuitry determines whether the GPIB COM should be a Talker and the target device a Listener or a Listener and the target device a Talker Interrupt Control Logic This circuitry generates and masks interrupts on GPIB conditions which correspond to the conditions that would cause the INS8250A circuit to generate an interrupt National Instruments Corporation 3 3 GPIB COM User Manual Function Description Section Three Direction Buffers These buffers control the direction in which data information travels GPIB Transceivers The GPIB COM is interfaced to the IEEE 488 bus by National Semiconductor 75160A and 75162A transceivers These integrated circuits are specifically designed to provide power up power down bus protection glitch free The GPIB COM counts as one IEEE 488 bus load thereby allowing an additional 14 devices to be connected before exceeding the bus loading restrictions imposed by the IEEE 488 GPI
17. e active or addressed Talker or Listener must be changed The Controller function is usually handled by a computer System Controller and Active Controller Although there can be multiple Controllers on the GPIB only one Controller at a time is Active Controller or Controller in Charge Active control can be passed from the current Active Controller to an idle Controller Only one device on the bus the System Controller can make itself the Active Controller GPIB Signals The interface bus consists of 16 signal lines and 8 ground return or shield drain lines The 16 signal lines are divided into three groups eight data lines e three handshake lines five interface management lines GPIB COM User Manual C 2 National Instruments Corporation Appendix C Operation of the GPIB Figure C 1 shows the arrangement of these signals on the GPIB cable connector 1 DIOS DIO6 DIO7 DIO8 REN GND TW PAIR W DAV GND TW PAIR W NRFD GND TW PAIR W NDAC GND TW PAIR W IFC 10 22 GND TW PAIR W SRQ GND TW PAIR W ATN SIGNAL GROUND Figure C 1 GPIB Cable Connector Data Lines The eight data lines DIO1 through DIOS carry both data and command messages All commands and most data use the 7 bit ASCII or ISO code set in which case the eighth bit DIO8 is unused or used for parity Handshake Lines Three lines asynchronously control the transfer of message bytes among devices The process is called a three
18. e rrr NU saan Y TE Ve PE UH EE YR VE REED ER 3 3 Iuterrupt Control LPIC au op pecias A mi esp mu EN SNR qe oa de ae 3 3 Directo bulferss RSR RTS NS Re nr rene 3 4 GPIB TrAHSCOEVOLS SR A RS a Jan aa aga eae ne 3 4 Section Four Running Diagnostic Tests eene utet e eiae n eni eaa ee eed 4 1 The GIPIB COME Test Commands 56d aee Bde dcn de acing a ure Moses 4 1 sL pribter S Le AS ES ne eene MEE e LR Ec EU 4 1 2 Plotter testae bee OUS Most easi tuas atau em nea ca CA eL 4 2 c change COME config rgtiOn ie eie et PO XR oe EPOD tetes 4 3 spi i 4 3 Section Five Programming the GPIB COM eese 5 1 The GPIB COM Re amp gISlets issue int TAIN eed PEOR PENA a e 5 1 Transmitter Holding ROS1stet s esee dci uses me anne eve YR E Ende gin 5 2 Receive Buffer Register i ette eid oe eden seated coun RE E EEES 5 3 Divisor Latch Least Significant Byte LSB Register 5 4 Divisor Latch Most Significant Byte MSB Register esses 5 4 Interrupt Enable Resister use eode petisti odes eese obse e tbe echarle 5 5 Interrupt Identification Reglster sons oec pert HERR fedens 5 7 National Instruments Corporation vii GPIB COM User Manual Contents Ene viunucutcd D 5 8 Modem Control Register 3 2 2 icto A SERE RUNG VR EIAS Rene 5 10 Line Status Register uec et ertet tee e decas saeua Ee Ran tatin 5 12 Mode Status RE BIS CC Sn a ed gea vhs lt a tepido ee Ed M d 5 14
19. e tt Soc a ere SO ed tot ide s Gods a ER X ERE C 5 Configuration RestriGHODS nement NOR Dues dee a Re oO Using C 7 GPIB COM User Manual viii National Instruments Corporation Figure 1 1 Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 Figure 2 6 Figure 3 1 Figure 4 1 Figure C 1 Figure C 2 Figure C 3 Table 2 1 Table 2 2 Table 5 1 Table 5 2 Table 5 3 Contents Figures GPIB COM BOAT iii nn nt e NOTE Sar fet Ut rom en 1 2 GPIB COM Parts Locator Diagram eee sites ted sere eee eee EN eee pw eda e etus l secius 2 1 Possible Settings for GPIB COM Jumpers 2 4 Jumper WI Se mesa au custo acd dose ere Rer vane 2 4 Switch Setting for REN OFF IFC ON SRQ ON and Listen Address 5 2 5 Listen Address Setting for Listen Address 10 Hex ess 2 6 Switch Setting for REN ON IFC OFF and SRQ OFF 2 7 Block Diagram of GPIB COM cedes teeedet eco 2s es eens ei peat vete ades 3 2 Plotter OUIDUL C otii eos televised ee Se SALE ee bea ecu E ted CD ER 4 2 GPIB Cable GOHBECIOE 5 ecco na eiit o tuse lectos bara Lal C 3 Linear Configuration of the GPIB Devices C 5 Star Configuration of GPIB Devices soe deer os ees tS ess tuos pens tio eco ane ee end CERE ned C 6 Tables IBM PE S rial Port Adapters nn ne tee ant ni Ne ne 2 3 Factory Default Settings and Optional Configurations 2 3 GPIB OM Registers ii e oed eu MS 5 1 Interrapt Types and Prion es
20. erface system through which interconnected electronic devices communicate Hewlett Packard invented the GPIB which they call the HP IB to connect and control programmable instruments manufactured by them Because of its high system data rate ceilings of from 250 kbytes sec to 1 Mbyte sec the GPIB quickly became popular in other applications such as intercomputer communication and peripheral control It was later accepted as the industry standard IEEE 488 The versatility of the system prompted the name General Purpose Interface Bus Types of Messages Devices on the GPIB communicate by passing messages through the interface system There are two types of messages e Device dependent messages often called data or data messages contain device specific information such as programming instructions measurement results machine status and data files e Interface messages manage the bus itself They are usually called commands or command messages Interface messages perform such functions as initializing the bus addressing and unaddressing devices and setting devices for remote or local programming Note The term command as used here should not be confused with some device instructions which are also called commands Such device specific instructions are actually data messages Talkers Listeners and Controllers There are three types of GPIB communicators A Talker sends data messages to one or more Listeners The Controller manages t
21. ermined by turning the equipment on and off one or more of the following suggestions may reduce or eliminate the problem e Operate the equipment and the receiver on different branches of your AC electrical system Move the equipment away from the receiver with which it is interfering e Relocate the equipment with respect to the receiver e Reorient the receiver s antenna Besure that the equipment is plugged into a grounded outlet and that the grounding has not been defeated with a cheater plug If necessary consult National Instruments or an experienced radio television technician for additional suggestions The following booklet prepared by the FCC may also be helpful How to Identify and Resolve Radio TV Interference Problems This booklet is available from the U S Government Printing Office Washington DC 20402 Stock Number 004 000 00345 4 Preface Introduction to the GPIB COM The GPIB COM is a high performance talk listen interface board that makes communication possible between IEEE 488 devices and IBM personal computers and compatibles hereafter referred to as PCs equipped with software that uses the serial ports Organization of This Manual This manual is divided into the following sections Section One ntroduction contains a brief description of the GPIB COM including a listing of its features accessories and components Section Two Configuration and Installation describes how to configure and install t
22. guration jumpers and switches NATIONAL INSTRUMENTS CORP GPIB COM o usies AJo tsosa gt Lseo a Ls175 a gt csoo UL ua u4 uia US o cs74 s 9 Lse7s gt t5174 Lse 4 UB Eaa us vid U11 RNICL TS LS123 701008 J p sit LSe44 b Lse44 U14 wis U16 u18 p cs e3 p 701000 cso 30 b L15244 u20 uei vee U24 D LS32 LS273 fp LS74 fo Lse4a4 u28 2 SPARE p Lsse f gt t5138 U44 U33 U34 5 SPARE E csse E Ls138 U4S u39 U40 COP RIGHT 1989 ASSY180750 01 REV Talk Listen Modes Base Address and Talk Listen Address Interrupt Selection and Special Function Selection Figure 2 1 GPIB COM Parts Locator Diagram National Instruments Corporation 2 1 GPIB COM User Manual Configuration and Installation Section Two When installing the GPIB COM you must determine which serial port the GPIB COM board will respond to and select the appropriate base address and interrupt level The GPIB COM can be configured to one of four base addresses e 3F8 for Serial Port 1 e 2F8 for Serial Port 2 e 3E8 for Serial Port 3 e 2E8 for Serial Port 4 Note DOS and BIOS only recognize base addresses 3F8 and 2F8 The GPIB COM is shipped from the factory set to 3F8 It must be reconfigured to another base address if another device such as a printer adapter ca
23. he GPIB COM into your system Section Three Function Description shows a block diagram of the GPIB COM and describes the functional components of the GPIB COM Section Four Running Diagnostic Tests describes how to run the diagnostic tests that are shipped with the GPIB COM Section Five Programming the GPIB COM presents a description of the GPIB COM Serial Port Emulator registers and information on programming the IBM serial adapter Appendix A Specifications lists the specifications of the GPIB COM board Appendix B Multiline Interface Command Messages contains an ASCII chart and a list of the corresponding GPIB messages Appendix C Operation of the GPIB describes GPIB terminology and protocol for users unfamiliar with the GPIB Related Documents The following documents contain information that may be helpful as you read this manual e ANSI IEEE Std 488 1978 IEEE Standard Digital Interface for Programmable Instrumentation IBM Options and Adapters Manual e IBM PC Technical Reference Manual e IBM Disk Operating System Manual e INS8250A Data Sheet National Semiconductor National Instruments Corporation v GPIB COM User Manual Preface Abbreviations Used in This Manual The following abbreviations are used in the text of this manual Q DIVIA GPIB COM User Manual is less than or equal to is greater than or equal to plus or minus ampere Celsius hexadecimal inch input output 1000 bytes
24. he computer sends data to the serial port and to talk when the computer is waiting to receive data from the serial port In order to be able to respond immediately to commands and data sent to the serial port the GPIB COM must be the GPIB System Controller and cannot work with other Controllers present National Instruments Corporation 3 1 GPIB COM User Manual Function Description Section Three Figure 3 1 shows a block diagram of the GPIB COM CORRE Interrupt Se Control Address IN S8250A Decoding Compatible Registers Direction Address Bus Em Jumpers PC I O Channel Mode Control Logic Acceptor Source Handshake Handshake GPIB Transceivers lt a Figure 3 1 Block Diagram of GPIB COM Direction Buffer GPIB COM User Manual 3 2 National Instruments Corporation Section Three Function Description GPIB COM Components The interface consists of the following functional components e Address Decoding e Configuration Jumpers e NS8250A Compatible Registers e GPIB Acceptor and Source Handshaking e Mode Control Logic Interrupt Control Logic Direction Buffers e GPIB Transceivers Address Decoding Address decoding monitors the PC address bus to recognize when a GPIB COM address is present and enables a read and or write to its registers Configuration Jumpers These onboard jumpers select the base address GPIB controller mode and interrupt request line used by the GPIB COM INS8250A Compatibl
25. he flow of information on the GPIB by sending commands to all devices Devices can be Talkers Listeners and or Controllers A digital multimeter for example is a Talker and may also be a Listener A printer or plotter is usually only a Listener computer on the GPIB often combines all three roles to manage the bus and communicate with other devices The GPIB is a bus like a typical computer bus except that the computer has its circuit cards interconnected via a backplane bus whereas the GPIB has standalone devices interconnected via a cable bus The role of the GPIB Controller can also be compared to the role of the computer s CPU but a better analogy is to the switching center of a city telephone system The switching center Controller monitors the communications network GPIB When the center Controller notices that a party device wants to make a call send a data message it connects the caller Talker to the receiver Listener National Instruments Corporation C 1 GPIB COM User Manual Operation of the GPIB Appendix C The Controller usually addresses a Talker and a Listener before the Talker can send its message to the Listener After the message is transmitted the Controller usually unaddresses both devices Some bus configurations do not require a Controller For example one device may only be a Talker called a talk only device and there may be one or more listen only devices A Controller is necessary when th
26. it of the Line Status Register to 0 puts the contents of that register on the GPIB data lines and begins the source handshake sequence When the Listener releases NDAC the THRE bit is set back to 1 and the GPIB COM waits for another byte to be written into the Transmitter Holding Register If the jumper is set to talk listen the GPIB COM assumes that the device connected to the GPIB can be addressed to listen or talk When the computer is powered on the GPIB COM sends the talk address that is set on the DIP switches addresses itself as a Listener and unasserts NRFD If the GPIB device sends a byte the GPIB COM accepts it stores it in the Receive Buffer Register and sets the DR bit of the Line Status Register At the end of the GPIB handshake it keeps NRFD asserted until the computer reads the byte from the Receive Buffer Register If the computer writes a byte to the Transmitter Holding Register the GPIB COM sends the GPIB device its listen address from the DIP switches and addresses itself to talk Then it sends the byte to the GPIB device which is now addressed as a Listener When the GPIB COM begins a source handshake it starts a 200 msec timer If the source handshake is completed before the 200 msec is expired the GPIB COM remains addressed to talk until the timer runs out If the computer writes another byte before the timer runs out the GPIB COM restarts the timer and sends the byte When 200 msec has passed since the last byte wa
27. meter megabyte megahertz millisecond read read write second volt volts direct current write vi National Instruments Corporation Contents Section One Introductio cov ito t p detuwtitbiastasetas udis ast nt et Dp att oti 1 1 GPIB COM Characteristics esser eite re es gear O AE VEU ANE EEAS 1 1 What Your Kit Should CODI eel eco Gratedea tene Md quisi qo UNO EMO e Nd tes 1 2 Optional BOuipriie HE soe o UE Sn ne oM sc Ds rue MTS 1 3 Section Two Configuration and Installation 2 1 COUT SUT AU OM ae a cue ART A tot earn ot etl ne ne tidy Suma Pare en An ne 2 1 Switch and Jumper SemiMgs uoce ou P eet ees sa pease mate EPA peste RE 2 3 Base I O Address and Interr pt SelectlOTL nn PEN TE VERO CU 2 3 abri MUI 2 4 Talk Listen Address and Special Function Selection 2 5 WPS Cell ALONE SR Sa Te iussa sub qM A a t d 2 7 Special Considerations When Using the GPIB COM eene 2 8 Section Three Function D scripHOl ecosedbotustu mecum von etta tum mite tatibus tide 3 1 The GPIB COM Interface 3 5 iien RR as qae P ent een 3 1 GPIB CONL COIBDOnDEDLU reco tpe eoe uide DNE RR re en Fate a udo tuos 3 3 Address Decoding asse e i RERO REN REA SI alain RUP dac iaa 3 3 onfisuration JUIIDEES sonia ti o tosta geh 3 3 INS8250A Compatible Registers 2 terreat rte pne peret e rib pee estesa E vex 3 3 GPIB Acceptor and Source Handshaking 3 3 Mode Control Logies
28. ming the GPIB COM You need to use this section only if you are writing your own serial port device driver The GPIB COM Registers IBM s serial adapter is a plug in card for the PC that handles RS 232 communication The main component of the adapter is an INS8250 Asynchronous Communications chip or its equivalent which is controlled by programming a set of registers on the I O channel The names of these registers and their I O addresses are given in Table 5 1 Each register is located at a certain offset from the base address of the board The addresses are given with an X for the first digit and a Y for the second digit where XY 3F for COMI base address 3F8 XY 2F for COM2 base address 2F8 XY 3E for COM3 base address 3E8 and XY 2E for COMA base address 2E8 Notice that sometimes two registers share the same I O address The DLAB bit bit 7 of the Line Control Register determines which register will respond when these addresses are accessed Note Throughout this section the term set will be used to mean that a bit is a logical 1 and clear will mean that the bit is a logical 0 Table 5 1 GPIB COM Registers I O Address Offset from Register XY 3F for COMI Base Address XY 2F for COM2 XY 3E for COM3 XY 2E for COM4 Transmitter Holding Register write XY8 DLAB 0 Receive Buffer Register read XY8 DLAB 0 Divisor Latch LSB Register read write XY8 DLAB 1 Divisor Latch MSB Register read write XY9 DLAB 1 Interrupt Enable Regis
29. nter or plotter you can configure the GPIB COM for a talk only mode In this mode the GPIB COM is always a Talker and never sends any interface commands To set the talk only mode change jumper W1 from T L to T as shown in Figure 2 3 a Talk Listen b Talk Only Default Figure 2 3 Jumper W1 Settings GPIB COM User Manual 2 4 National Instruments Corporation Section Two Configuration and Installation Talk Listen Address and Special Function Selection The GPIB COM interface board has eight onboard DIP switches you can use to configure the GPIB controller responsibilities In the talk listen mode the first five switches set the talk or listen address of the external device s that will be attached to the GPIB COM In the talk only mode the GPIB COM does not send a talk or listen address The three remaining switches REN IFC and SRQ have the following special functions Note An asterisk after a signal name indicates that the signal is inverted negative logic REN Asserts unasserts the Remote Enable REN line that places an instrument in remote mode The ON position enables REN The OFF position disables REN IFC Enables disables the Interface Clear IFC option on the GPIB COM If enabled the GPIB COM issues an IFC when it is initialized The ON position enables IFC on initialization The OFF position holds IFC unasserted SRQ Enables disables the Service Request SRQ option If enabled the GPIB COM monitors
30. on Tr DCD Data Carrier Detect Bit This bit reflects the inverse of the serial port DCD input signal On the GPIB COM this bit is always clear 6r RI Ring Indicator Bit This bit reflects the inverse of the serial port RI input signal On the GPIB COM this bit is always clear 5r DSR Data Set Ready Bit This bit reflects the inverse of the serial port DSR input signal On the GPIB COM this bit is always set to indicate that the interface is ready to transfer data 4r CTS Clear to Send Bit This bit reflects the inverse of the serial port CTS input signal On the GPIB COM this bit is the logical AND of the DTR and RTS bits of the Modem Control Register 3r DDCD Delta Data Carrier Detect Bit This bit is set when the serial port DCD input signal changes state and cleared when the processor reads the Modem Status Register On the GPIB COM this bit is always clear GPIB COM User Manual 5 14 National Instruments Corporation Section Five Bit Mnemonic 2r TERI Ir DDSR Or DCTS National Instruments Corporation Programming the GPIB COM Description Trailing Edge Ring Indicator Bit This bit is set when the serial port RI input signal changes from a logical 1 to a logical 0 and cleared when the processor reads the Modem Status Register On the GPIB COM this bit is always clear Delta Set Ready Bit This bit is set when the serial port DSR input signal changes state and cleared when the processor reads the Modem Stat
31. rated by the INS8250 The high four bits are not used and are permanently cleared The lower four bits each enable one type of interrupt as listed below Bit Mnemonic Description 7 Ar w 0 Reserved Bits 7 through 4 These bits always read as 0 3r w MS Modem Status Interrupt Enable Bit This bit enables a modem status interrupt when set to logical 1 The modem status interrupt occurs when any of bits 0 through 3 of the Modem Status Register are set to logical 1 This bit is identical on the GPIB COM and the INS8250 but bits 0 through 3 of the Modem Status Register are set for different conditions as noted under the Modem Status Register description 2r w RLS Receive Line Status Interrupt Enable Bit This bit enables a line status interrupt when set The line status interrupt occurs when any of bits 1 through 4 of the Line Status Register become set This bit is identical on the GPIB COM and the INS8250 but bits 1 through 4 of the Line Status Register are set for different conditions as noted under the Line Status Register description National Instruments Corporation 5 5 GPIB COM User Manual Programming the GPIB COM Bit Mnemonic 1r w THR Or w RDA GPIB COM User Manual Section Five Description Transmitter Holding Register Interrupt Enable Bit This bit enables a transmitter holding register empty interrupt when set The transmitter holding register empty interrupt occurs when the INS8250 becomes ready to send another char
32. ration Section Four Running Diagnostic Tests When it is finished the following message appears on the screen Plotter test finished Please check output to plotter with user manual instructions If the plotter does not respond or the output on the plotter does not match Figure 4 1 check again to be sure that all of the connections are tight and the jumpers are all set correctly Try the test again If it still does not work write down any error messages that appear and call National Instruments c change COM configuration This command is used to change the base address of the GPIB COM to match the actual board settings If you have changed the jumper settings to something different than the default settings you must run this command When this command is selected the following menu appears This program assumes the GPIB COM is configured at base address 3F8 COM1 Enter the number of the correct address 1 base address 3F8 COM1 2 base address 2F8 COM2 Enter 1 2 or return for no change Type in the number of the address that you have configured the board to The computer prints out your choice and returns to the main menu q quit This command ends the test program and returns to DOS National Instruments Corporation 4 3 GPIB COM User Manual Section Five Programming the GPIB COM This section presents a description of the GPIB COM Serial Port Emulator registers and information on program
33. rd or a built in serial port is already at that address DOS has reserved device names for the serial ports it finds in the system COMI and COM2 The serial port adapters are named in the order in which they are found When the computer is powered on DOS searches the serial port addresses for installed adapters It first searches 3F8 then 2F8 If only one device is installed that device is named COMI regardless of what its I O address is If there is more than one serial device installed the first one found is assigned COMI and the second one found is assigned COM2 Some communications software also recognizes COMG base address 3E8 and COMA base address 2E8 If you wish to use COMG or COMA set the jumpers to the desired base address as shown in Figure 2 2 DOS and BIOS do not recognize COM3 or COM4 Consult your software documentation to see which interrupt level if any is required If interrupts are not used the jumper can be removed or stored with only one side on a pin The GPIB COM may need to be reconfigured if its interrupt level conflicts with another device If the base I O address of the GPIB COM does not conflict with any other device in your computer and the GPIB COM still does not work with your software package reconfigure the GPIB COM to a different interrupt level GPIB COM User Manual 2 2 National Instruments Corporation Section Two Configuration and Installation Table 2 1 shows the standard base I O address and
34. rinter test finished Please check output to printer with user manual instructions The output on the printer should read NATIONAL INSTRUMENTS GPIB COM DIAGNOSTIC TEST S amp 0123456789 lt gt ABCDEFGHIJKLMNOPQORSTUVWXYZ _ abcdefghijkl mnopgrstuvwxyz f amp 0123456789 lt gt ABCDEFGHI IKLMNOPQRSTUVWXY Z _ abcdefghijklmnopgrstuvwxyz S amp 0123456789 lt gt ABCDEFGHI JKLMNOPORSTUVWXYZ __ abcdefghi klmnopgrstuvwxyz S S amp 0123456789 lt gt ABCDEFG TJKLMNOPQRS TUVWXYZ _ abcdefghijklmnopqrstuvwxyz Gy EB el Pee If the printer does not respond an error message appears on the screen along with a message telling you to recheck all of your connections and jumper settings If the test still fails after everything has been checked write down the error message if any and call National Instruments 2 plotter test Select this test to verify the configuration of the GPIB COM when connecting it to a GPIB HP GL plotter This test will send output to the plotter When this command is selected the computer prints the following message Starting plotter test As illustrated in Figure 4 1 the plotter begins to draw four ovals AO NATIONAL INSTRUMENTS GPI BAZOM DIAGNOSTIC TEST D C2 Figure 4 Plotter Output GPIB COM User Manual 4 2 National Instruments Corpo
35. s iu o RS ipd od ena Sosy NON RET 5 7 Word Length Select Bus ni se te ees pct Sete iSc etaniere 5 9 National Instruments Corporation ix GPIB COM User Manual Section One Introduction This section contains a brief description of the GPIB COM interface and a list of its characteristics and components GPIB COM Characteristics The National Instruments GPIB COM is a high performance talk listen interface that converts data between a standard serial port format and IEEE 488 General Purpose Interface Bus GPIB format for use with IEEE 488 printers and plotters It can be used with any serial port software on the PC The GPIB COM looks like a standard serial port to the IBM PC operating system and software It can be used to interface IEEE 488 devices to any PC software that uses the serial ports The GPIB COM has the following hardware features emulates the standard PC serial adapter interface so that no additional software is needed can be configured as either COMI COM2 COM3 or COM4 compatible with any software using the serial ports on the IBM PC and its compatibles transparent addressing of unaddressed Talkers and Listeners choice of talk only mode for use with listen only printers and plotters choice of REN mode which operates an instrument in the remote mode choice of SRQ enable which allows monitoring of asynchronous service requests choice of IFC mode which sends an interface clear when the computer is powered on
36. s Corporation Appendix C Operation of the GPIB Configuration Restrictions To achieve the high data transfer rate that the GPIB is designed for the physical distance between devices and the number of devices on the bus is limited The following restrictions are typical e A maximum separation of 4 m between any two devices and an average separation of 2 m over the entire bus e A maximum total cable length of 20 m e No more than 15 devices connected to each bus with at least two thirds powered on National Instruments Corporation C 7 GPIB COM User Manual User Comment Form National Instruments encourages you to comment on the documentation supplied with our products This information helps us provide quality products to meet your needs Tite GPIB COM User Manual Edition Date June 1990 Part Number 320197 01 Please comment on the completeness clarity and organization of the manual If you find errors in the manual please record the page numbers and describe the errors Thank you for your help Name Title Company Address Phone Mail to Technical Publications National Instruments Corporation 6504 Bridge Point Parkway MS 53 02 Austin TX 78730 5039
37. s a read only register Writing to the line status register will not change its contents The function of each bit in this register is explained below Bit Mnemonic Description Tr 0 Reserved Bit This bit always reads as 0 6r TEMT Transmitter Shift Register Empty Bit This bit is cleared when a character is transferred from the Transmitter Holding Register to the Transmitter Shift Register and set when the character has been shifted out of the Shift Register onto the serial output line On the GPIB COM there is no shift register so this bit behaves exactly the same as the THRE bit 5r THRE Transmitter Holding Register Empty Bit This bit is cleared when the processor writes a character into the Transmitter Holding Register and set when the character has been transmitted and the INS8250 is ready to send another character This bit functions identically on the GPIB COM and the INS8250 4r BI Break Interrupt Bit This bit is set to logical 1 when the serial data input remains in the logical 0 state for longer than one full word transmission time On the GPIB COM this bit is always clear GPIB COM User Manual 5 12 National Instruments Corporation Section Five Bit Mnemonic 3r FE 2r PE lr OE Or DR National Instruments Corporation Programming the GPIB COM Description Framing Error Bit This bit is set when the received character does not have a valid stop bit On the GPIB COM this bit is always clear Pari
38. s down for REN ON IFC OFF and SRQ OFF Off 1 On 0 C used for setting Listen Address This side down for logic This side down for logic 0 ai il Figure 2 6 Switch Setting for REN ON IFC OFF and SRQ OFF Installation Once you have changed verified and recorded the switches and jumper settings you are ready to install the GPIB COM The following steps are general installation instructions Consult the user manual or technical reference manual of your personal computer for specific instructions and warnings 1 Turn off your computer 2 Remove the plug from its power source 3 Remove the top cover or access port to the I O channel 4 Remove the expansion slot cover on the back panel of your computer 5 Insert the GPIB COM in an unused full length slot with the IEEE 488 receptacle sticking out of the opening of the back panel It may be a tight fit but do not force the board into place 6 Screw the right angle mounting bracket of the GPIB COM to the back panel rail of your computer National Instruments Corporation 2 7 GPIB COM User Manual Configuration and Installation Section Two 7 Check the installation 8 Replace the expansion slot cover of your computer 9 Connect the GPIB cable to the GPIB COM Special Considerations When Using the GPIB COM The GPIB COM does not support XON XOFF protocols If your application software uses XON XOFF protocols send your printer and plotter outp
39. s written the GPIB COM sends the talk address and addresses itself to listen again If a byte was waiting in the Receive Buffer Register when the computer wrote to the Transmitter Holding Register the GPIB COM remembers this and when it becomes a Listener again it asserts NRFD until the computer reads the byte from the Receive Buffer Register National Instruments Corporation 5 17 GPIB COM User Manual Appendix A Specifications This appendix lists the specifications of the GPIB COM board Power Requirement 5 VDC 5 Physical Dimensions T O Connector Operating Environment Component Temperature Relative Humidity Emissions Storage Environment Temperature Relative Humidity National Instruments Corporation 0 75 A typical 4 2 in by 8 75 in IEEE 488 Standard 24 pin 0 to 70 C 596 to 9096 noncondensing FCC Class B 55 to 125 C 596 to 9096 noncondensing A 1 GPIB COM User Manual Appendix B Multiline Interface Command Messages The following tables are multiline interface messages sent and received with ATN TRUE National Instruments Corporation B 1 GPIB COM User Manual Multiline Interface Command Messages Appendix B Multiline Interface Messages Hex Oct Dec ASCII Msg Hex Oct Dec ASCII Msg 00 000 0 NUL 20 040 32 SP MLAO 01 001 1 SOH GTL 21 041 33 MLA1 02 002 2 STX 22 042 34 MLA2 03 003 3 ETX 23 043 35 MLA3 04 004 4 EOT SDC 24 044 36 MLA4 05 005 5 ENQ PPC 25
40. ter read write XY9 DLAB 0 Interrupt Identification Register read XYA Line Control Register read write XYB Modem Control Register read write XYC Line Status Register read XYD Modem Status Register read XYE 0 0 0 1 1 2 3 4 5 6 The following pages describe the functions of each register on the serial adapter and on the GPIB COM For a more complete description of the serial adapter refer to the JBM Options and Adapters Manual National Instruments Corporation 5 1 GPIB COM User Manual Programming the GPIB COM Section Five Transmitter Holding Register Offset from Base I O Address 0 Register Address XF8 DLAB bit in Line Control Register 0 7 6 5 4 3 2 1 0 Lee oe eh ee ee W The Transmitter Holding Register contains the character to be sent to the serial output with bit 0 being the least significant and bit 7 the most significant It functions identically on the GPIB COM and the INS8250 Bit Mnemonic Description 7 0w D 7 0 Data Bits 7 through 0 GPIB COM User Manual 5 2 National Instruments Corporation Section Five Programming the GPIB COM Receive Buffer Register Offset from Base I O Address 0 Register Address XF8 DLAB bit in Line Control Register 0 7 6 5 4 3 2 1 0 R ENENEME EXE The Receive Buffer Register contains the character received from the serial input with bit 0 being the least significant and bit 7 the most significant It functions identically on the GPIB COM and the INS8250
41. truments makes no commitment to update nor to keep current the information contained in this document Copyright Under the copyright laws this manual may not be copied photocopied reproduced translated in whole or in part without the prior written consent of National Instruments Corporation Trademark IBM is a registered trademark of International Business Machines Corporation FCC DOC Radio Frequency Interference Compliance This equipment generates and uses radio frequency energy and if not installed and used in strict accordance with the instructions in this manual may cause interference to radio and television reception This equipment has been tested and found to comply with 1 the limits for a Class B computing device in accordance with the specifications in Part 15 of U S Federal Communications Commission FCC Rules and 2 the limits for radio noise emissions from digital apparatus set out in the Radio Interference Regulations of the Canadian Department of Communications DOC These regulations are designed to provide reasonable protection against interference from the equipment to radio and television reception in residential areas There is no guarantee that interference will not occur in a particular installation However the chances of interference are much less if the equipment is used according to this instruction manual If the equipment does cause interference to radio or television reception which can be det
42. ty Error Bit This bit is set when the received character does not have the correct parity Itis cleared when the processor reads the Line Status Register On the GPIB COM this bit is set when the SRQ line of the GPIB is asserted When the special function selection DIP switch has been set to disable the SRQ feature this bit is always clear Overrun Error Bit This bit is set when a new character is received and stored in the Receive Buffer Register before the processor reads the previous character thus overwriting and destroying the previous character It is cleared when the processor reads the Line Status Register On the GPIB COM this bit is always clear Data Ready Bit This bit is set when a character has been received and stored in the Receive Buffer Register It is cleared when the processor reads the Receive Buffer Register This bit functions identically on the GPIB COM and the INS8250 5 13 GPIB COM User Manual Programming the GPIB COM Section Five Modem Status Register Offset from Base I O Address 6 Register Address XFE 7 6 5 4 3 2 1 0 R pees Le Loe oe om Dom os The Modem Status Register gives the state of the modem control lines and tells whether any of these lines have changed state since the register was last read This register is read only on the GPIB COM Writing to this register will not change its contents The function of each bit in this register is explained below Bit Mnemonic Descripti
43. us Register On the GPIB COM this bit is always clear Delta Clear to Send Bit This bit is set when the CTS input changes state and cleared when the processor reads the Modem Status Register On the GPIB COM this bit is the logical AND of the DTR and RTS bits of the Modem Control Register 5 15 GPIB COM User Manual Programming the GPIB COM Section Five Programming the Serial Adapter The operation of the serial adapter is controlled by software either IBM BIOS or an application To transfer data to and from the serial port the communications parameters must first be set up in the following manner 1 Load the baud rate divisor into the divisor latch 2 Store the RS 232 parameters in the Line Control Register 3 Send the modem control signals by writing to the Modem Control Register 4 Enable interrupts if used by writing to the appropriate bits in the Interrupt Enable Register Once the control registers have been programmed correctly the software can transmit and receive serial data by polling interrupts or both Polling Method In the polled method of operation the Line Status Register is continuously read to check if the Data Ready Bit is set When this bit becomes set the Receive Buffer Register is read to get the character that just came from the serial port and the process continues To transmit data the Line Status Register is polled until the Transmitter Holding Register Empty Bit is set A byte can then
44. ut to a file on disk From DOS send your file to the GPIB COM by using the DOS command copy filename COMI copy filename COM2 The DOS MODE command is used to set the RS 232 parameters that will be used when COMI and COM are accessed through DOS Sometimes a timeout error may occur when writing through the GPIB COM to a slow device such as a printer or a plotter If this happens use the MODE command to disable the timeout function by typing MODE COM1 12 P Some software applications use the COM port baud rate setting to control the data transmission speed To obtain the fastest possible transfer rates set the baud rate setting to 9600 baud The P at the end disables the timeout For more information on the MODE command refer to the JBM Disk Operating System Manual This command can also be used in an autoexec bat file to disable timeouts when you start up the computer GPIB COM User Manual 2 8 National Instruments Corporation Section Three Function Description This section contains a block diagram of the GPIB COM followed by a description of each of its functional components The GPIB COM Interface The GPIB COM is a completely transparent interface between GPIB devices and any IBM PC software that uses serial ports A set of I O registers identical to those on the standard IBM serial adapter is used On the GPIB side the GPIB COM includes a limited subset of interface functions that address a GPIB device to listen when t
45. wire interlocked handshake and it guarantees that message bytes on the data lines are sent and received without transmission error NRFD not ready for data NRED indicates when a device is ready or not ready to receive a message byte The line is driven by all devices when receiving commands and by Listeners when receiving data messages NDAC not data accepted NDAC indicates when a device has or has not accepted a message byte The line is driven by all devices when receiving commands and by Listeners when receiving data messages National Instruments Corporation C 3 GPIB COM User Manual Operation of the GPIB Appendix C DAV data valid DAV tells when the signals on the data lines are stable valid and can be accepted safely by devices The Controller drives DAV when sending commands and the Talker drives it when sending data messages The way in which NRFD and NDAC are used by the receiving device is called the Acceptor Handshake Likewise the sending device uses DAV in the Source Handshake Interface Management Lines Five lines are used to manage the flow of information across the interface ATN attention The Controller drives ATN true when it uses the data lines to send commands and false when it allows a Talker to send data messages IFC interface clear The System Controller drives the IFC line to initialize the bus to become Controller In Charge REN remote enable The System Controller drives the REN line
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