Using Service Request (SRQ) and Serial POLL You must configure your bus controller to respond to th e IEEE- 488
service request (SRQ) interrupt to use this capability. Use the status
byte enable register (SRE) to select which summary bits will set the
low-level IEEE-488 SRQ signal. When the status byte “request service”
bit (bit 6) is set, an IEEE-488 SRQ interrupt message is automatically
sent to the bus controller. The bus controller may then poll th e
instruments on the bus to identify which one requested se rvic e (t h e one
with bit 6 set in its status byte). The request service bit is only cleared
by reading the status byte using an IEEE-488 serial poll or by reading
the event register wh ose summary bit is caus i ng the service reque st.
To read the status byte summary register, send the IEEE-488 serial poll
message. Querying the summary register will return a decimal value
which corresponds to the binary-weighted sum of the bits set in the
register. Serial poll will automatically clear the “request service” bit in
the status byte summary register. No other bits are affected. Performing
a serial poll will not affect instrument throughput.
Caution The IEEE-488.2 standard does not ensure synchronization between your
bus controller prog ram and the instrument. U se the *OPC? command to
guarantee that commands previousl y sent to the instrument hav e
completed. Executing a serial poll before a *RST , *CLS, or other
commands have completed can cause previous condit ions to be reported.
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Chapter 4 Remote Interface Reference
The SCPI Status Model
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