Service Request

The instrument can send a service request (SRQ) to the controller. Usually this service request initiates an interrupt at the controller, to which the control program can react appropriately. As evident from the figure The status registers, an SRQ is always initiated if one or several of bits 2, 3, 4, 5 or 7 of the status byte are set and enabled in the SRE. Each of these bits combines the information of a further register, the error queue or the output buffer. The ENABle parts of the status registers can be set so that arbitrary bits in an arbitrary status register initiate an SRQ. In order to use the possibilities of the service request effectively, all bits should be set to "1" in the enable registers SRE and ESE.

Examples (cf. "The status registers"):

Use command "*OPC" to generate an SRQ

Set bit 0 in the ESE (Operation Complete)
Set bit 5 in the SRE (ESB)

After its settings have been completed, the instrument generates an SRQ.

Indication of an event (e.g. overloading of used input connector) by means of an SRQ with the controller:

Set bit 7 in the SRE (sum bit of the STATus:OPERation register)

The following steps depend on the secondary address (0 £ <SecAddr> £ 29) assigned to the function group and signalling mode used.

0 £ <SecAddr> £ 14

Set bit 8 in the STATus:OPERation:ENABle register.
Set bit <SecAddr>-1 in the STATus:OPERation:CMU:SUM1:ENABle register
Set bit 0 in the STATus:OPERation:CMU:SUM1:CMU
<SecAddr>:ENABle register.

15 £ <SecAddr> £ 29

Set bit 9 in the STATus:OPERation:ENABle register.
Set bit <SecAddr>-16 in the STATus:OPERation:CMU:SUM2:ENABle register
Set bit 0 in the STATus:OPERation:CMU:SUM2:CMU
<SecAddr>:ENABle register.

When the event assigned to bit no. 0 of the STATus:OPERation:CMU:SUM1|2:CMU<SecAddr> register occurs (e.g. when the input connector is overloaded in function group RF Non Signalling) the instrument generates a SRQ.

The same procedure can be applied to find out which event caused an SRQ:

STB?
Query STAT:OPER:EVENT?
Query STAT:OPER:CMU:SUM1|2:EVENT? (function group, signalling mode)
QuerySTAT:OPER:CMU:SUM1|2:CMU1...15:EVENT?(measurement)

The SRQ is the only possibility for the instrument to become active on its own. Each controller program should set the instrument such that a service request is initiated in the case of malfunction. The program should react appropriately to the service request.