Agilent Technologies ESA-E Series Programmer's Manual page 36

If you are using the status bits and the analyzer mode is changed, the
NOTE
status bits should be read, and any error conditions resolved, prior to
switching modes. Error conditions that exist prior to switching modes
cannot be detected using the condition registers after the mode change.
This is true unless they recur after the mode change, although
transitions of these conditions can be detected using the event registers.
Changing modes resets all SCPI status registers and mask registers to
their power-on defaults. Hence any event or condition register masks
must be re-established after a mode change. Also note that the power
up status bit is set by any mode change, since that is the default state
after power up.
Status Subsystem Commands
Individual status registers can be set and queried using the commands
in the STATus subsystem in
guide. There are two methods used to programmatically detect and
manage error conditions or changes in analyzer status. Either method
allows you to monitor one or more conditions. The two methods are:
• The Polling Method
• The Service Request (SRQ) Method
The Polling Method
In the polling method, the analyzer has a passive role. It only tells the
controller that conditions have changed when the controller asks the
right question. The polling method works well if you do not need to
know about changes the moment they occur. This method is very
efficient.
Use the polling method when either:
— your programming language/development environment does not
— you want to write a simple, single-purpose program and don't want
The Service Request (SRQ) Method
The SRQ method allows timely communication of information without
requiring continuous controller involvement. Using this method, the
analyzer takes a more active role. It tells the controller when there has
been a condition change without the controller asking. The SRQ method
should be used if you must know immediately when a condition
changes. This is in contrast to the polling method, which requires the
program to repeatedly read the registers to detect a change.
Use the SRQ method when either:
— you need time-critical notification of changes
Chapter 2
Use Status Registers to Determine the State of Analyzer Events and Conditions
support SRQ interrupts
the added complexity of setting up an SRQ handler
Chapter 5, "Language Reference"
Status Registers
in this
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