Appendix F
GPIB Basics
F-4
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Figure F-1 shows the arrangement of these signals and lines on the GPIB
cable connector (a * suffix indicates that the signal is active low).
Figure F-1.
GPIB Connector Signals and Lines
Data Lines
The eight data lines, DIO1* through DIO8*, 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-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)
NRFD* 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.
DIO1*
DIO2*
DIO3*
DIO4*
EOI*
DAV*
NRFD*
NDAC*
IFC*
SRQ*
ATN*
SHIELD
1
2
3
4
5
6
7
8
9
10
11
12
DIO5*
DIO6*
DIO7*
DIO8*
REN*
GND (Twisted Pair with DAV*)
GND (Twisted Pair with NRFD*)
GND (Twisted Pair with NDAC*)
GND (Twisted Pair with IFC*)
GND (Twisted Pair with SRQ*)
GND (Twisted Pair with ATN*)
SIGNAL GROUND
13
14
15
16
17
18
19
20
21
22
23
24
