1 Power Meter Remote Operation
90 N1911A/1912A P-Series Power Meters Programming Guide
Using the Operation Complete Commands
The *OPC? and *OPC commands allow you to maintain synchronization between
the computer and the power meter. The *OPC? query command places an ASCII
character 1 into the power meter’s output queue when all pending power meter
commands are complete. If your program reads this response before continuing
program execution, you can ensure synchronization between one or more
instruments and the computer.
The *OPC command sets bit 0 (Operation Complete) in the Standard Event Status
Register when all pending power meter operations are complete. By enabling this
bit to be reflected in the Status Register, you can ensure synchronization using the
GPIB serial poll.
Procedure
– Send a device clear message to clear the power meter’s output buffer.
– Clear the event registers with the *CLS (clear status) command.
– Enable operation complete using the *ESE 1 command (standard event
register).
– Send the *OPC? (operation complete query) command and enter the result to
assure synchronization.
– Send your programming command string, and place the *OPC (operation
complete) command as the last command.
– Send the *STB? (status byte query) command to poll the register. This
command does not clear the status byte summary register.
In GPIB mode only you can use a serial poll to check to see when bit 5
(standard event) is set in the status byte summary register. You could also
configure the power meter for an SRQ interrupt by sending *SRE 32 (status
byte enable register, bit 5).
For LAN and USB use the *STB? command. See “Using *STB? to Read the Status
Byte” on page 83.
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