PSI BOX Reference
IEEE 488 Introduction
by a particular device.
ATN Attention.
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All devices on the IEEE bus must monitor the ATN line.
The attention line is used by the controller to specify how data
on the data bus is to be interpreted and which devices must
respond to the data. The ATN line is set true by the controller
when it sends interface messages, such as device talk and listen
address, secondary addresses, and polling configuration messages.
The ATN is set false by the controller so that the active talker
can send device dependent messages, such as data and
programming information, to the active listeners.
IFC Interface Clear.
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The IFC line, interface clear, is used by the controller to
place the bus interface in a known inactive state. Only the
System Controller can set the IFC line, all other instruments
must monitor and respond to IFC. The System Controller may
set IFC true at any time.
REN Remote Enable.
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The REN line, remote enable, sends the remote message.
REN must be true for an device to operate under remote control
from a system controller, otherwise the device is programmed
locally from its front panel. Only the System Controller can set
the REN line, all other instruments must monitor and respond to
REN by returning to local control whenever it becomes false.
The System Controller may set REN true at any time.
SRQ Service Request.
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The SRQ line, service request, is used by a device to
indicate the need for attention and to request an interruption of
the current sequence of events. The controller can clear the SRQ
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Chapter 2
