HP 8920B - Page 238

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Common Command Descriptions
*WAI (Wait To Complete)
The *WAI command stops the Test Set from executing any further commands or
queries until all commands or queries preceding the *WAI command have
completed.
Example BASIC statement
OUTPUT 714;"DISP RFG;RFG:OUTP ’Dupl’;*WAI;AMPL 0 dBm"
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.
CAUTION: The *WAI command should not be used for determining if a Call Processing Subsystem
state command has completed successfully. Call Processing Subsystem states do not
complete, a state is either active or not active. Using the *WAI command with a Call
Processing Subsystem state command results in a deadlock condition. The Test Set will not
process any further HP-IB commands unitl the Call Processing Subsystem command
preceeding the *WAI command completes but the command never ‘completes’.
For example, the following command sequence should not be used:
OUTPUT 714;"CALLP:ACTive;*WAI;:CALLP:REGister"
The *WAI command should not be used with any of the following Call
Processing Subsystem commands: :ACTive, :REGister, :PAGE, :HANDoff,
:RELease.
The Call Processing Subsystem Status Register Group should be used to control program
flow. Refer to chapter 8, "Programming The Call Processing Subsystem" for
information on controlling program flow using the Call Processing Subsystem Status
Register Group.