90 API Command Reference
Personal488 User's Manual For Windows95 and Windows NT
PPoll
Syntax
INT WINAPI PPoll(DevHandleT devHandle);
devHandle
refers to either an interface or an external device. If
devHandle
refers to an
external device, then the
PPoll
command acts on the hardware interface to which the
external device is attached.
Returns
-1
if error
otherwise, a number in the range 0 to 255
Mode
CA
Bus States
ATN
••
EOI, *EOI
Example
errorcode = PPoll(ieee);
See Also
PPollConfig, PPollUnconfig, PPollDisable, SPoll
The
PPoll
(Parallel Poll) command is used to request status information from many bus devices
simultaneously. If a device requires service then it responds to a Parallel Poll by asserting one of the
eight IEEE 488 bus data lines (
DIO1
through
DIO8
, with
DIO1
being the least significant). In this
manner, up to eight devices may simultaneously be polled by the controller. More than one device can
share any particular
DIO
line. In this case, it is necessary to perform further Serial Polling (
SPoll
) to
determine which device actually requires service.
Parallel Polling is often used upon detection of a Service Request (
SRQ
), though it may also be
performed periodically by the controller. In either case,
PPoll
responds with a number from
0
to
255
corresponding to the eight binary
DIO
lines. Not every device supports Parallel Polling. Refer to the
manufacturer’s documentation for each bus device to determine if
PPoll
capabilities are supported.
Summary of Contents for OMB-PER-488/W95
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