Technical data

Power Meter Remote Operation 1
N1911A/1912A P-Series Power Meters Programming Guide 53
How to Use Register
There are two methods to access the information in status groups:
• the polling method, or
• the service request (SRQ) method. (GPIB mode only)
Use the polling method when:
• your language/development environment does not support SRQ
interrupts.
• you want to write a simple, single purpose program and do not want
to add the complexity of setting an SRQ handler.
Use the SRQ method when you:
• need time critical notification of changes.
• are monitoring more than one device which supports SRQ interrupts.
• need to have the controller do something else while it is waiting.
• cannot afford the performance penalty inherent to polling.
The Condition Polling Method
In this polling method, the power meter has a passive role. It only informs
the controller that conditions have changed when the controller asks.
When you monitor a condition with the polling method, you must:
1 Determine which register contains the bit that monitors the
condition.
2 Send the unique query that reads that register.
3 Examine the bit to see if the condition has changed.
The polling method works well if you do not need to know about the
changes the moment they occur. The SRQ method is more effective if you
must know immediately when a condition changes. Detecting an immediate
change in a condition using the polling method requires your program to
continuously read the registers at very short intervals. This is not
particularly efficient and there is a possibility that an event may be
missed.