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Appendix A
GPIB Basics
GPIB-120B User Manual
A-4
ni.com
Interface Management Lines
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
Description
ATN
(attention)
Controller drives ATN true when it sends
commands and false when it sends data messages.
IFC
(interface clear)
System Controller drives the IFC line to initialize
the bus and make itself CIC.
REN
(remote enable)
System Controller drives the REN line 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 Controller.
EOI
(end or identify)
Talker uses the EOI line to mark the end of a data
message. Controller uses the EOI line when it
conducts a parallel poll.