SRQ
Service Requests
This appendix describes the spectrum analyzer service request (SRQ) capability. A service
request is a spectrum analyzer output that tells the operator or computer that a specific event
has taken place in the spectrum analyzer.
When writing programs, service requests can be used to interrupt the computer program
sequence, causing the program to branch to a subroutine. For example, by using service
requests, the computer can perform other operations while the spectrum analyzer is sweeping.
When the sweep is completed, the computer can service the spectrum analyzer by changing the
spectrum analyzer state or reading data from the memory.
Note
Service requests do not work with computers that have an RS-232 interface.
Not all service requests are available with some HP-IB computers. Refer to the
manuals supplied by your computer’s manufacturer.
When making a service request, the spectrum analyzer places the I/O interface SRQ line true
and the spectrum analyzer displays SRQ with an octal coded number. Setting the SRQ line true
announces to the computer that the spectrum analyzer requires attention. The computer can
then command the spectrum analyzer to send its “status byte.” The status byte indicates the
type of service request. The status byte is the binary equivalent of the octal SRQ number.
Note
If the spectrum analyzer display annotation has been blanked, the service
request notation will not appear.
A serial polling technique must be used by the computer to test for service
requests. The spectrum analyzer does not respond to parallel polling.
A service request can be cleared from the display by pressing
C-1,
doing an instrument
preset, or by executing a remote command query.
Status Byte Definition
The status byte sent by the spectrum analyzer determines the nature of the service request.
The meaning of each bit of the status byte is explained in Table A-l.
SRQ A-l
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