Agilent Technologies ESA-E Series Programmer's Manual page 43

Status Registers
Use Status Registers to Determine the State of Analyzer Events and Condition s
The SRQ process sets the GPIB SRQ line true . It also sets the statu s
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 devic e
requires service .
If your program enables the controller to detect and respond to servic e
requests, it should instruct the controller to perform a serial poll whe n
the GPIB SRQ line is set true . Each device on the bus returns th e
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 .
NOTE
When you read the analyzer status byte register with a serial poll, the
RQS bit is reset to O . Other bits in the register are not affected .
Restarting a measurement with the : INITiate command can cause th e
measuring bit to pulse low. A low pulse causes an SRQ if the statu s
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 th e
method.
The examples below show how to use the : STATus command to perform
the following tasks :
• Check the analyzer hardware and firmware status .
Do this by querying the condition registers which continuousl y
monitor status. These registers represent the current state of th e
analyzer. Bits in a condition register are updated in real time . When
the condition monitored by a particular bit becomes true, the bit i s
set to 1 . When the condition becomes false, the bit is reset to O .
• Monitor a particular bit (condition), or bits.
Chapter 2 2-9