User`s manual

Chapter 4 93
IEEE Common Commands
Common Command Descriptions
*OPC (Operation Complete)
The *OPC command allows for synchronization between the Test Set
and an external controller. The *OPC command causes the Test Set to
set bit 0, Operation Complete, in the Standard Event Status Register to
the TRUE, logic 1, state when the Test Set completes all pending
operations. Detection of the Operation Complete message can be
accomplished by continuous polling of the Standard Event Status
Register using the *ESR? common query command. However, using a
service request eliminates the need to poll the Standard Event Status
Register thereby freeing the controller to do other useful work.
NOTE The Test Set contains signal generation and signal measurement
instrumentation. The instrument control processor is able to query the
signal measurement instrumentation to determine if a measurement
cycle has completed. However, the instrument control processor is not
able to query the signal generation instrumentation to determine if the
signal(s) have settled. In order to ensure that all signals have settled to
proper values, the instrument control processor initiates a one-second
delay upon receipt of the *OPC, *OPC? and *WAI commands. In
parallel with the one-second timer the instrument control processor
commands all active measurements to tell it when the measurement(s)
are done. When all active measurements are done and the one-second
timer has elapsed, the *OPC, *OPC? and *WAI commands are satisfied.
If the *OPC, *OPC? or *WAI common commands are used to determine
when a measurement has completed and the measurement is either in
the OFF State or unavailable (four dashed lines on CRT display “- - - -”),
the *OPC, *OPC? or *WAI command will never complete.