How To Use Registers - Agilent Technologies 8712ET Programmer's Manual

Using Status Registers

How to Use Registers

How to Use Registers
There are two methods of accessing the information in status registers:
• the direct-read method
• the service request (SRQ) method
In the direct-read method, the analyzer is passive. It only tells the
controller that conditions have changed when the controller asks the
right question. In the SRQ method, the analyzer is more active. 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 following steps are used to monitor a condition with the direct read
method:
1. Determine which register contains the bit that monitors the
condition.
2. Send the unique GPIB query that reads that register.
3. Examine the bit to see if the condition has changed.
The direct-read method works well when it is not necessary to know
about changes the moment they occur. It does not work well if immediate
knowledge of the condition change is needed. A program that used this
method to detect a change in a condition would need to continuously read
the registers at very short intervals. The SRQ method is better suited for
that type of need.
5-6 Programmer's Guide