Measurement Computing Personal488 rev.3.0 - Manual (Page 108)

Personal488 for Windows 95/98/Me/NT/2000 04-10-01 API Reference 6-40
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
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.