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November 1985
Interface Management Lines
Five lines are used to manage the flow of information across the
interface.
ATN (attention)
The Controller drives ATN true when it uses the data lines to send
commands and false when it allows a Talker to send data messages.
IFC (interface clear)
The System Controller drives the IFC line to initialize the bus to
become Controller-In-Charge.
REN (remote enable)
The System Controller drives the REN line, which is used 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 Active Controller with the SRQ line.
EOI (end or identify)
The EOI line has two purposes. The Talker uses it to mark the end
of a message string. The Active Controller uses it to tell devices to
identify their responses in a parallel poll.
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 at
each end. This design allows devices to be connected in either a
linear or a star configuration, or a combination of the two. See
the following figures.
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APPENDIX D - OPERATION OF THE GPIB
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