Keithley SourceMeter 2425, Service Manual, Page: 126 / 141

Model 2425 Service Manual Command Reference B-11
Generating an SRQ on error
To program the instrument to generate an IEEE-488 bus SRQ (Service Request) when an
error occurs, send the following command: *SRE 4. This command will enable SRQ when
the EAV bit is set. You can then read the status byte and error queue as outlined above to
check for errors, and to determine the exact nature of the error.
Detecting calibration step completion
When sending remote calibration commands, you must wait until the instrument com-
pletes the current operation before sending another command. You can use either *OPC?
or *OPC to help determine when each calibration step is completed.
Using the *OPC? query
With the *OPC? (operation complete) query, the instrument will place an ASCII 1 in the
output queue when it has completed each step. To determine when the OPC response is
ready, do the following:
1. Repeatedly test the MAV (Message Available) bit (bit 4) in the status byte and wait
until it is set. (You can request the status byte by using the *STB? query.)
2. When MAV is set, a message is available in the output queue, and you can read the
output queue and test for an ASCII 1.
3. After reading the output queue, repeatedly test MAV again until it clears. At this
point, the calibration step is completed.
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
(operation complete bit) in the standard event enable register, allowing operation
complete 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:SENS 2;*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 command.