Agilent Technologies ESA-E Series Programmer's Manual page 38

The SRQ process sets the GPIB SRQ line true. It also sets the status
byte request service (RQS) bit to 1. Both actions are necessary to inform
the controller that the analyzer requires service. Setting the SRQ line
only informs the controller that some device on the bus requires service.
Setting the RQS bit allows the controller to determine which device
requires service.
If your program enables the controller to detect and respond to service
requests, it should instruct the controller to perform a serial poll when
the GPIB SRQ line is set true. Each device on the bus returns the
contents of its status byte register in response to this poll. The device,
whose RQS bit is set to 1, is the device that requested service.
When you read the analyzer status byte register with a serial poll, the
NOTE
RQS bit is reset to 0. Other bits in the register are not affected.
Restarting a measurement with the :INITiate command can cause the
measuring bit to pulse low. A low pulse causes an SRQ if the status
register is configured to SRQ upon end-of-measurement. To avoid this,
perform the following steps:
1. Set :INITiate:CONTinuous off.
2. Set/enable the status registers.
3. Restart the measurement (send :INITiate).
Example of Monitoring Conditions Using the :STATus
Command
Use the following steps to monitor a specific condition:
1. Determine which register contains the bit that reports the condition.
2. Send the unique SCPI query that reads that register.
3. Examine the bit to see if the condition has changed.
4. Act upon the cause of the condition and the SRQ to re-enable the
The examples below show how to use the :STATus command to perform
the following tasks:
• Check the analyzer hardware and firmware status.
• Monitor a particular bit (condition), or bits.
Chapter 2
Use Status Registers to Determine the State of Analyzer Events and Conditions
method.
Do this by querying the condition registers which continuously
monitor status. These registers represent the current state of the
analyzer. Bits in a condition register are updated in real time. When
the condition monitored by a particular bit becomes true, the bit is
set to 1. When the condition becomes false, the bit is reset to 0.
Status Registers
2-9