Operation of the GPIB
Appendix A
GPIB-140 User Manual
A-4
© National Instruments Corp.
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. This design
allows devices to be linked in either a linear or a star configuration, or a combination of
the two. See Figures A-1 and A-2.
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
interconnection applications.
The GPIB uses negative logic with standard TTL (transistor-transistor logic) level. When
DAV is true, for example, it is a TTL low level (
≤
0.8V), and when DAV is false, it is a
TTL high level (
≥
2.0V).
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
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