Measurement Computing Serial488A - Manual (Page 57)

4.8
When the Serial488A is addressed to listen, it accepts data from the
active talker and outputs this data through the serial interface. It substitutes
the selected serial terminators for the received IEEE bus terminators.
4.6.3 Device Clear (DCL and SDC)
Device Clear resets the Serial488A's IEEE input and serial input
buffers. Any pending data and Service Requests (SRQ), including the
information they convey, are lost.
4.6.4 Interface Clear (IFC)
IFC places the Serial488A in the Talker/Listener Idle State. It clears
any pending requests for service (SRQ). The condition which caused the
SRQ remains unmodified.
4.6.5 Serial Poll Enable (SPE)
When Serial Poll Enabled, the Serial488A sets itself to respond to a
serial poll with its serial poll status byte if addressed to talk. When the
serial poll byte is accepted by the controller, any pending SRQs are
cleared. The Serial488A will continue to try to output its serial poll
response until it is 'Serial Poll Disabled' by the controller.
4.6.6 Serial Poll Disable (SPD)
Disables the Serial488A from responding to serial polls by the
controller.