2-8 Programmer’s Guide
Synchronizing the Analyzer and a Controller
Controlling Execution of Overlapped Commands
Using *WAI and *OPC?
*WAI
The following example describes the use of the *WAI command. For this
discussion, remember that a sequential command holds off the
processing of subsequent commands until it has been completely
processed. An overlapped command does not.
10 OUTPUT @Rfna;"command1"
20 OUTPUT @Rfna;"command2;*WAI"
30 OUTPUT @Rfna;"command3;"
40 OUTPUT @Rfna;"command4"
50 END
In the example above, commands are sent and completed in the following
order:
• Commands 1 through 4 are sent to the analyzer as fast as the GPIB
bus traffic will allow. The program sending the commands may very
well end before any command has been completed.
• Command 1 begins execution first.
• If both commands 1 and 2 are overlapped types, the order in which
they finish initiation depends on the commands. The order of
completion is unknown.
• Commands 3 and 4 will not be started until both commands 1 and 2
have finished initiation.
• Command 3 will begin execution before command 4.
• If all four commands are overlapped types, the order in which they
complete execution is unknown.
NOTE Because *WAI only controls the order of the initiation stage of
commands, rather than the order of completion, it is strongly
recommended that *OPC? be used whenever sequential operation of
overlapping commands is required.
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