Using Service Request (Srq) And Serial Poll - Keysight 34420A User Manual

The status byte summary register is cleared when:
– You execute a *CLS (clear status) command.
– Querying the standard event and questionable data registers will clear only the
The status byte enable register (request service) is cleared when:
– You turn on the power and you have previously configured the meter using the
– You execute a *SRE 0 command.
The status byte enable register will not be cleared at power-on if you have
previously configured the meter using *PSC 0.

Using Service Request (SRQ) and Serial POLL

You must configure your bus controller to respond to the 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 the
instruments on the bus to identify which one requested service (the 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 whose
summary bit is causing the service request.
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.
The IEEE-488.2 standard does not ensure synchronization between your bus
CAUTION
controller program and the instrument. Use the *OPC? command to
guarantee that commands previously sent to the instrument have
completed. Executing a serial poll before a *RST, *CLS, or other commands
have completed can cause previous conditions to be reported.
Keysight 34420A User's Guide
respective bits in the summary register.
*PSC 1 command.
Remote Interface Reference 4
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