Table A-1. Gpib Handshake Lines; Table A-2. Gpib Interface Management Lines - National Instruments NI-488.2 User Manual

Handshake Lines
Interface Management Lines
© National Instruments Corporation
Three hardware handshake lines asynchronously control the transfer of
message bytes between devices. This process is a three-wire interlocked
handshake, and it guarantees that devices send and receive message bytes
on the data lines without transmission error. Table A-1 summarizes the
GPIB handshake lines.
Line
NRFD
(not ready for data)
NDAC
(not data accepted)
DAV
(data valid)
Five hardware lines manage the flow of information across the bus.
Table A-2 summarizes the GPIB interface management lines.

Table A-2. GPIB Interface Management Lines

Line
ATN
(attention)
IFC
(interface clear)
REN
(remote enable)
SRQ
(service request)
EOI
(end or identify)

Table A-1. GPIB Handshake Lines

Description
Listening device is ready/not ready to receive a
message byte. Also used by the Talker to signal
high-speed GPIB transfers.
Listening device has/has not accepted a message
byte.
Talking device indicates signals on data lines are
stable (valid) data.
Description
Controller drives ATN true when it sends
commands and false when it sends data messages.
System Controller drives the IFC line to initialize
the bus and make itself CIC.
System Controller drives the REN line to place
devices in remote or local program mode.
Any device can drive the SRQ line to
asynchronously request service from the Controller.
Talker uses the EOI line to mark the end of a data
message. Controller uses the EOI line when it
conducts a parallel poll.
A-3
Appendix A GPIB Basics
NI-488.2 User Manual for Windows