Keithley 2303, Service Manual, Page: 88 / 104

Calibration Reference B-7
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 completes
the current operation before sending another command. You can use either *OPC or *OPC? to
determine when each calibration step is completed.
Using the *OPC command
Using *OPC is the preferred method to detect the end of each calibration step. To use *OPC,
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:STEP0 14;*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.
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.
Using the *OPC? query
With the *OPC? (operation complete) query, the instrument will place an ASCII 1 in the out-
put 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.
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