Using Service Request (SRQ) and Serial Poll You must configure your computer to respond to the IEEE-488 service
request (SRQ) interrupt to use this capability. Use the Status Byte
enable register (*SRE command) to select which condition bits will assert
the IEEE-488 SRQ line. If bit 6 (RQS) transitions from a “0” to a “1”,
then an IEEE-488 service request message is sent to your computer.
The computer may then poll the instruments on the interface bus to
identify which one is asserting the service request line (the instrument
with bit 6 set in its Serial Poll response).
Note: When a Serial Poll is issued, bit 6 (RQS) is clea red in the Status
Byte (no other bits are affected) and the service request line is cleared.
To read the Status Byte condition register, send an IEEE-488 Serial Poll
message. Querying the condition register will return a decimal value
which corresponds to the binary-weighted sum of the bits set in the
register. Performing a Serial Poll will not affect measurement
throughput.
Note: Unlike other commands, a Serial Poll is executed immediately.
Therefore, the status indicated by a Serial Poll may not necessarily
indicate the affect of the most recent command. Use the *OPC? command
to guarantee that commands previously sent to the instrument have
completed before executing a Serial Poll.
Using *STB? to Read the Status Byte The *STB? command is similar to a Serial Poll but it is processed like
any other instrument command. The *STB? command returns the same
result as a Serial Poll but bit 6 is not cleared as long as the enabled
conditions remain.
The *STB? command is not handled automatically by the IEEE-488 bus
interface hardware and will be executed only after previous commands
have completed. You cannot clear an SRQ using the *STB? command.
Chapter 5 Remote Interface Reference
The SCPI Status System
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