A Service Request, SRQ, is sent by a non-active controller on the IEEE-488 bus. If the computer is the active controller or if the device-selector or the IO-path specifies address information, an error is generated.
To request service, the response value must have bit six set. The SRQ line will remain set until polled by the active controller or anotherREQUESTstatement is executed with bit six clear.