Reading Analyzer Data; Command Query - HP 8753E Programming And Command Reference Manual

Output Queue
Whenever an output-data command is received, the analyzer puts the
data into the output queue (or buffer) where it is held until the system
controller outputs the next read command. The queue, however, is only
one event long: the next output-data command will overwrite the data
already in the queue. Therefore, it is important to read the output
queue immediately after every query or data request from the analyzer.

Command Query

All instrument functions can be queried to find the current ON/OFF
state or value. For instrument state commands, append the question
mark character ('?) to the command to query the state of the functions.
Suppose the operator has changed the power level from the analyzer's
front panel. The computer can ascertain the new power level using the
analyzer's command-query function. If a question mark is appended
to the root of a command, the analyzer will output the value of that
function. For instance,
outputs the current RF source power at the test port. When
the analyzer receives
source power level. This condition illuminates the analyzer front-panel
talk light (T). In this case, the analyzer transmits the output power to
the controller.
ON/OFF commands can also be queried. The reply is a one (1) if the
function is ON or a zero (0) if it is OFF. For example, if a command
controls an active function that is underlined on the analyzer display,
querying that command yields a one (1) if the command is underlined
or a zero (0) if it is not. As another example, there are nine options on
the format menu and only one option is underlined at a time. Only the
underlined option will return a one when queried.
For instance, send the command string
dual-channel display is switched ON, the analyzer will return a one (1)
to the instrument controller.
Similarly, to determine if phase is being measured and displayed, send
the command string
will return a one (1) if phase is currently being displayed. Since the
command only applies to the active channel, the response to the
HP-IB Progr amming and Command Reference Guide
7 DE; sets the source power to 7 dB, and
it prepares to transmit the current RF