Programming instructions

Programming the Status Register System
Accessing Status Register Information
Chapter 3 109
informs the controller that some device on the bus requires service. Setting the RQS bit allows
the controller to determine which signal generator requires service.
This process is initiated if both of the following conditions are true:
• The corresponding bit of the Service Request Enable Register is also set to 1.
• The signal generator does not have a service request pending.
A service request is considered to be pending between the time the signal generator’s SRQ
process is initiated and the time the controller reads the status byte register.
If a program enables the controller to detect and respond to service requests, it should
instruct the controller to perform a serial poll when SRQ is true. Each device on the bus
returns the contents of its status byte register in response to this poll. The device whose
request service summary bit (RQS) bit is set to 1 is the device that requested service.
NOTE When you read the signal generator’s Status Byte Register with a serial poll,
the RQS bit is reset to 0. Other bits in the register are not affected.
If the status register is configured to SRQ on end-of-sweep or measurement and
the mode set to continuous, restarting the measurement (INIT command) can
cause the measuring bit to pulse low. This causes an SRQ when you have not
actually reached the “end-of-sweep” or measurement condition. To avoid this,
do the following:
1. Send the command INITiate:CONTinuous OFF.
2. Set/enable the status registers.
3. Restart the measurement (send INIT).