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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).

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Agilent Technologies E4438C Manuale delle Istruzioni Pagina 115