Programmer’s Guide 2-7
Synchronizing the Analyzer and a Controller
Controlling Execution of Overlapped Commands
NOTE *OPC only informs you when all currently executing commands have
completed execution. It does not hold off the processing of subsequent
commands. No commands should be sent to the analyzer between
sending the *OPC command and receiving the service request. Any
commands sent will be executed and may affect how the instrument
responds to the previously sent *OPC.
The *CLS and *RST commands cancel any preceding *OPC? or *OPC.
Executing overlapped commands are still completed, but their
completion is not reported in either the status register or the output
queue. Two GPIB bus management commands — Device Clear (DCL)
and Selected Device Clear (SDC) — also cancel any preceding *OPC? or
*OPC.
NOTE Use *WAI, *OPC? or *OPC whenever overlapped commands are used. A
recommended technique is to send *OPC? at the end of each group of
commands.
CAUTION ALWAYS trigger an individual sweep (using *OPC? and waiting for the
reply) before reading data over the bus or executing a marker function.
The analyzer has the ability to process the commands it receives faster
than it can make a measurement. If the measurement is not complete
when the data is read or a marker search function is executed, the
results are invalid.
The command to use (in an IBASIC OUTPUT statement) is:
OUTPUT @Hp8711;"ABOR;:INIT:CONT OFF;:INIT;*OPC?"
ENTER @Hp8711;Opc_done
or another form of the INITiate[1|2][:IMMediate] command
combined with the *OPC? query.
Refer to “Taking Sweeps” in the Example Programs Guide for more
information.
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