3 Remote Interface Reference
132 Keysight E364xA User’s and Service Guide
Using *STB? to read the status byte
The *STB? (Status Byte query) 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 the “request service” bit (bit 6) is not cleared.
The *STB? command is not handled automatically by the IEEE-488 bus interface
hardware and will be executed only after previous commands have completed.
Polling is not possible using the *STB? command. Executing the *STB? command
does not clear the Status Byte summary register.
Using the Message Available bit (MAV)
You can use the Status Byte “Message Available” bit (bit 4) to determine when
data is available to read into your bus controller. The power supply subsequently
clears bit 4 only after all messages have been read from the output buffer.
To interrupt your bus controller using SRQ
1 Send a device clear message to clear the power supply’s output buffer (for
example, CLEAR 705).
2 Clear the event registers with the *CLS (clear status) command.
3 Set up the enable register masks. Execute the *ESE command to set up the
Standard Event register and the *SRE command for the Status Byte.
4 Send the *OPC? (operation complete query) command and enter the result to
ensure synchronization.
5 Enable your bus controller’s IEEE-488 SRQ interrupt.
The IEEE-488 standard does not ensure synchronization between your bus
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.
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