Appendix F - Parallel Polling - National Instruments GPIB-MAC User Manual

November 1985
Appendix F
Parallel Polling
A Parallel Poll allows a GPIl3 controller to obtain information from
several devices on the GPIB in one operation. The controller polls
configured devices and reads back a single response byte that
contains one bit of information from each device. From this
information the controlIer can determine which devices need
servicing.
Operation
A device is configured by sending it its listen address and a parallel
poll enable (PPE) message. There are 16 possible PPE messages,
hex 60 - hex 6F. The bits in the PPE message have the following
meaning:
0
when 0 (hex 6X), parallel poll is enabled.
U -
when 1 (hex 7X), parallel poll is disabled
when the device's ist (individual status) bit
S -
matches the S bit, the device will assert the
appropriate data line true. hex 60 - hex 67
set S to 0, hex 68 - hex 6F set S to 1.
The value "n" in bits O-2 corresponds to one
DIO
of the DIO lines l-8, where n corresponds to
DIO line n+l. Thus a value of 2 (binary 010)
corresponds to DIO line 3.
117

APPENDIX F - PARALLEL POLLING

U
I I
11
S
I