Sequoia Series 183
7.7 SCPI Command Completion
SCPI commands sent to the power source are processed either sequentially or in parallel. Sequential
commands finish execution before a subsequent command begins. Parallel commands allow other
commands to begin executing while the parallel command is still executing. Commands that affect list
and trigger actions measurements and calibration are among the parallel command.
The *WAI, *OPC, and *OPC? common commands provide different ways of indicating when all
transmitted commands, including any parallel ones, have completed their operations. The syntax and
parameters for these commands are described in chapter 5. Some practical considerations for using
these commands are as follows:
*WAI This prevents the power source from processing subsequent commands until
all pending operations are completed except for transients.
*OPC? This places a 1 in the Output Queue when all pending operations have
completed. Because it requires your program to read the returned value
before executing the next program statement, *OPC? can be used to cause
the controller to wait for commands to complete before proceeding with its
program.
*OPC 1 This sets the OPC status bit when all pending operations have completed.
Since your program can read this status bit on an interrupt basis, *OPC allows
subsequent commands to be executed.
TRIG:STATe? This query will report the state of the transient trigger subsystem and will
return IDLE, ARM or BUSY to allow the user monitor the state of the trigger
system.
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