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3
C H A P T E R
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 this command is being
executed, or if the next command must wait until this command is completed
before its execution begins.
Sequential/Overlapped Commands
All FPM-8200 device-dependent commands are executed in an overlapped
manner: subsequent commands may begin before the current command is
completed. Some common commands are sequential: the Next command must
wait until this command is completed.
The *WAI (common command) is an example of a sequential command which
forces the next command to wait until the no-operation-pending 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)
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.
Input/Output Buffer
GPIB program statements (input) and FPM-8200 responses (output) can be any
length. These data I/O transfers are done by Direct Memory Access (DMA) in
blocks of up to 256 bytes. Transfers longer than 256 bytes are done with multiple
data blocks. This information should generally not be of concern, except for
troubleshooting compatibility issues with a particular GPIB controller. If you are
encountering these issues, ILX Lightwave Customer Service can probably help.
The FPM-8200 normally responds to multiple queries in a single response output.
For example:
This is a typical response:
36
FPM-8200
R E M O T E O P E R A T I O N
Command Timing
Mes?; Rad?; Mode?; Err?
TEST1,DEC,W,0
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Troubleshooting
