Agilent Technologies N5181A/82A User Manual download pdf (Page 161)

Agilent N518xA, E8663B, E44x8C, and E82x7D Signal Generators Programming Guide 151

Programming the Status Register System

Accessing Status Register Information

The query command *SRE? returns the decimal value of the sum of the bits previously enabled with

the *SRE <num> command.

To query the Status Byte Register, send the command *STB?. The response will be the decimal sum

of the bits which are set to 1. For example, if bit 7 and bit 3 are set, the decimal sum will be 136

(bit 7 = 128 and bit 3 = 8).

NOTE Multiple Status Byte Register bits can assert an SRQ, however only one bit at a time can set

the RQS bit. All bits that are asserting an SRQ will be read as part of the status byte when

it is queried or serial polled.

The SRQ process asserts SRQ as true and sets the status byte’s RQS bit to 1. Both actions are

necessary to inform the controller that the signal generator requires service. Asserting SRQ 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 (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).

Status Register SCPI Commands

Most monitoring of signal generator conditions is done at the highest level using the IEEE 488.2

common commands listed below. You can set and query individual status registers using the

commands in the STATus subsystem.

*CLS (clear status) clears the Status Byte Register by emptying the error queue and clearing all

the event registers.

*ESE, *ESE? (event status enable) sets and queries the bits in the Standard Event Enable Register

which is part of the Standard Event Status Group.

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Agilent Technologies N5181A/82A User Manual Page 161