Newport FPM-8220, User Manual

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April 2018 38 FPM-8220
Command Timing
This section describes, for each device-dependent command, whether that command is performed in
an overlapped or sequential manner. In other words, it states whether the next command may begin
while the first is being executed, or if it must wait until the first command is completed before its
execution begins. See the Operation Complete Definition earlier in this chapter for conditions about
setting the operation complete flag.
Sequential / Overlapped Commands
All device-dependent commands are executed in an overlapped manner: subsequent commands
may begin before the current command has completed. Some common commands are sequential;
the next command must wait until this command has completed. All device-dependent commands
are executed in an overlapped manner, except the “DELAY” command which is sequential. The
operation complete flag is set after the conditions outlined in the Operation Complete Definition have
been satisfied.
*WAI is an example of a sequential command which forces the next command to wait until the no-
operation flag is true. This is essentially the same as waiting for the OPC flag to become true,
because the no-operations-pending flag is used to set the OPC flag (bit 0 of the Standard Event
Status Register).
Commands which change the status of the instrument limits, or change its mode, step value, or
status enable registers, will not have their OPC flag set until all current writing to non-volatile memory
has been completed. This ensures the OPC flag is never set prematurely.
Query Response Timing
Query responses are evaluated at the time the query request is parsed, and not at the time the
response message is sent. In most cases, this does not create a problem since the time between
parsing a query and sending its response is small.