3 Remote Interface Reference
SCPI Status Registers
116 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
commands. 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.
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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