Analyzer
Operation
Held Commands
The analyzer cannot process HP-IB commands while executing certain
key commands known as “held” commands. For example, SING; is a
held command because it requires the analyzer to take one sweep of
data before executing any other commands.
Once a held command is received, the analyzer will read new commands
into the input buffer, but it will not begin the execution of any
commands until the completion of the held command. When the
15-character
input buffer is full, the analyzer will put hold on the bus
until it is able to process the commands in the buffer.
Note
Commands that call a calibration class are held if there
is just one standard in the class, since such commands
trigger a measurement.
Operation Complete
Occasionally, there is a need to know when certain analyzer operations
have been completed. There is an operation-complete function (OPC)
that allows a synchronization of programs with the execution of
certain key commands. This mechanism is activated by issuing
OFT
;
or
I~IPI~‘?;
prior to an OPC-compatible command. The status byte or
ESR operation-complete bit will then be set after the execution of the
OPC-compatible command. For example, issuing
ICIF’I:;
S
I
HI;.;
causes the
OPC bit to be set when the single sweep is Enished. Issuing UPC?
;
in
place of the
CIF’C:;
causes the analyzer to output a one (1) when the
command execution is complete. The analyzer will halt the computer
by not transmitting the one (1) until the command has completed. For
example, executing
OFT’?;
F’RE:3
j
,
and then immediately querying the
analyzer causes the bus to halt until the instrument preset is complete
and the analyzer outputs a one (1).
As another example, consider the timing of sweep completion. Send
the command string
5WET
3
S;
OPIZ’?
j
S
I
HG;
to the analyzer. This
string sets the analyzer sweep time to 3 seconds, and then waits for
completion of a single sweep to respond with a one (1). The computer
should be programmed to read the number one (1) response from the
analyzer indicating completion of the single sweep. At this point a valid
trace exists and the trace data could be read into the computer.
1-12 HP-IB
Programtui
ng and Command Reference Guide
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