Keysight Technologies EPM-P Series Programming Manual page 99

Power Meter Remote Operation 1
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 GPIB 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.
The SRQ method
When a bit of the Status Register is set and has been enabled to assert SRQ (*SRE
command), the power meter sets the GPIB SRQ line true. This interrupt can be
used to interrupt your program to suspend its current operation and find out what
service the power meter requires. Refer to your computer and language manuals
for information on how to program the computer to respond to the interrupt.
To allow any of the Status Register bits to set the SRQ line true, you must enable
the appropriate bit(s) with the *SRE command. For example, if your application
requires an interrupt whenever a message is available in the output queue (Status
Register bit 4, decimal weight 16). To enable bit 4 to assert SRQ, use the
command *SRE 16
You can determine which bits are enabled in the Status Register using *SRE?.
NOTE
This command returns the decimal weighted sum of all the bits.
Procedure
– Send a bus device clear message.
– Clear the event registers with the *CLS (clear status) command.
– Set the *ESE (standard event register) and *SRE (status byte register) enable
masks.
Keysight EPM-P Series Programming Guide 99