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Parallel Poll
Status Reporting
B-8
Parallel poll is a controller initiated operation which is used to obtain
information from several devices simultaneously. When a controller
initiates a Parallel Poll, each device returns a Status Bit via one of the DIO
data lines. Device DIO assignments are made by the controller using the
PPC (Parallel Poll Configure) sequence. Devices respond either
individually, each on a separate DIO line; collectively on a single DIO
line; or any combination of these two ways. When responding collectively,
the result is a logical AND (True High) or logical OR (True Low) of the
groups of status bits.
Figure B-2 shows the Parallel Poll Data Structure. The summary bit is
sent in response to a Parallel Poll. This summary bit is the "ist" (individual
status) local message.
The Parallel Poll Enable Register determines which events are
summarized in the ist. The *PRE command is used to write to the enable
register and the *PRE? query is used to read the register. The *IST?
query can be used to read the "ist" without doing a parallel poll.
HP 18528/1853B
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