Measurement Computing Analyzer488 - Manual (Page 145)

Section 4 Serial Controller
4.51
PPOLL
The Parallel Poll command, PPOLL,causes the Analyzer488 to conduct a
Parallel Poll of bus devices. It is used to request status information from many bus
devices simultaneously. If a device requires service then it will respond 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 be polled
simultaneously by the controller. More than one device can share any particular DIO
line. In this case it is necessary to perform a Serial Poll command, 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 will
respond 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 Parallel Poll capabilities are
supported.
This command does not have a query option.
TYPE High Level Controller command
SYNTAX PPOLL
RESPONSE Number in the range of 0 to 255
MODE High Level Controller
BUS STATES ATN•EOI,, *EOI
QUERY None
RESPONSE
EXAMPLE PRINT#1,"PPOLL" Conduct a Parallel Poll
INPUT#1,PPSTAT Receive the PPOLL status
PRINT PPSTAT and print it.