Agilent Technologies Signal Analyzer N9030a - Manual (Page 129)

3 Programming the Analyzer
STATus Subsystem
What Are Status Register SCPI Commands
Most monitoring of the instrument conditions is done at the highest level using the IEEE common
commands indicated below. Complete command descriptions are available in the IEEE commands
section at the beginning of the language reference. Individual status registers can be set and
queried using the commands in the STATus subsystem of the language reference.
•
*CLS (clear status) clears the status byte by emptying the error queue and clearing all the event
registers.
•
*ESE, *ESE? (event status enable) sets and queries the bits in the enable register part of the
standard event status register.
•
*ESR? (event status register) queries and clears the event register part of the standard event
status register.
•
*OPC, *OPC? (operation complete) sets the standard event status register to monitor the
completion of all commands. The query stops any new commands from being processed until
the current processing is complete, then returns a ‘1’.
•
*PSC, *PSC? (power-on state clear) sets the power-on state so that it clears the service request
enable register and the event status enable register at power on.
•
*SRE, *SRE? (service request enable) sets and queries the value of the service request enable
register.
•
*STB? (status byte) queries the value of the status byte register without erasing its contents.
How to Use the Status Registers
A program often needs to be able to detect and manage error conditions or changes in instrument
status. There are two methods you can use to programmatically access the information in status
registers:
•
The polling method
•
The service request (SRQ) method
In the polling method, the instrument has a passive role. It only tells the controller that conditions
have changed when the controller asks the right question. In the SRQ method, the instrument
takes a more active role. It tells the controller when there has been a condition change without the
controller asking. Either method allows you to monitor one or more conditions.
The polling method works well if you do not need to know about changes the moment they occur.
The SRQ method should be used if you must know immediately when a condition changes. To
detect a change using the polling method, the program must repeatedly read the registers.
Use the SRQ method when:
•
you need time-critical notification of changes
Remote Language Compatibility Measurement Application Reference 129