Appendix A Operation of the GPIB

© National Instruments Corporation A-5 GPIB-120A User Manual

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 connector at each end. With this design, devices can be linked in

either a linear configuration (shown in Figure A-2) or a star configuration (shown in

Figure A-3), or a combination of the two.

The standard connector is the Amphenol or Cinch Series 57 Microribbon or Amp Champ type.

An adapter cable using a non-standard cable and/or connector is used for special interconnecting

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 ( ≥ 2.0 V).

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24
DIO5
DIO6
DIO7
DIO8
REN
GND (TW PAIR W/DAV)
GND (TW PAIR W/NRFD)
GND (TW PAIR W/NDAC)
GND (TW PAIR W/IFC)
GND (TW PAIR W/SRQ)
GND (TW PAIR W/ATN)
SIGNAL GROUND
DIO1
DIO2
DIO3
DIO4
EOI
DAV
NRFD
NDAC
IFC
SRQ
ATN
SHIELD

Figure A-1. GPIB Connector and the Signal Assignment