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Protocols
Functional Elements
Message Communication and System Functions
A-2
The protocols of IEEE 488.2 define the overall scheme used by the
controller and the instrument to communicate. This includes defining
when it is appropriate for devices to talk or listen, and what happens when
the protocol is not followed.
Before proceeding with the description of the protocol, a few system
components should be understood.
Input Buffer. The input buffer of the instrument is the memory area
where commands and queries are stored prior to being parsed and
executed. It allows a controller to send a string of commands to the
instrument which could take some time to execute, and then proceed to
talk to another instrument while the first instrument is parsing and
executing commands.
Output Queue. The output queue of the instrument is the memory area
where all output data ( -C response messages > ) are stored until read by
the controller.
Parser. The instrument's parser is the component that interprets the
commands sent to the instrument and decides what actions should be
taken. "Parsing" refers to the action taken by the parser to achieve this
goal. Parsing and executing of commands begins when either the
instrument recognizes a c program message terminator > (defined later
in this appendix) or the input buffer becomes full. If you wish to send a
long sequence of commands to be executed and then talk to another
instrument while they are executing, you should send all the commands
before sending the c program message terminator > .
HP 16528/1653B
Programming Reference
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