Keithley 2520, Service Manual, Page: 131 / 137

Model 2520 Pulsed Laser Diode Test System Service Manual Calibration Reference B-11
Using the *OPC command
The *OPC (operation complete) command can also be used to detect the completion of
each calibration step. In order to use *OPC to detect the end of each calibration step, do
the following:
1. Enable operation complete by sending *ESE 1. This command sets the OPC (oper-
ation complete bit) in the standard event enable register, allowing operation com-
plete status from the standard event status register to set the ESB (event summary
bit) in the status byte when operation complete is detected.
2. Send the *OPC command immediately following each calibration command. For
example:
:CAL:PROT:SOUR2 20;*OPC
Note that you must include the semicolon (;) to separate the two commands, and
that the *OPC command must appear on the same line as the calibration command.
3. After sending a calibration command, repeatedly test the ESB (Event Summary)
bit (bit 5) in the status byte until it is set. (Use *STB? to request the status byte.)
4. Once operation complete has been detected, clear OPC status using one of two
methods: (1) use the *ESR? query, then read the response to clear the standard
event status register, or (2) send the *CLS command to clear the status registers.
Note that sending *CLS will also clear the error queue and operation complete
status.
Generating an SRQ on calibration complete
An IEEE-488 bus SRQ (service request) can be used to detect operation complete instead
of repeatedly polling the Model 2520. To use this method, send both *ESE 1 and *SRE 32
to the instrument, then include the *OPC command at the end of each calibration com-
mand line, as covered above. Clear the SRQ by querying the ESR (using the *ESR?
query) to clear OPC status, then request the status byte with the *STB? query.
Refer to your controller's documentation for information on detecting and servicing SRQs.