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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,<parallel poll response>, *EOI

QUERY None

RESPONSE

EXAMPLE

PRINT#1,"PPOLL"

Conduct a Parallel Poll

INPUT#1,PPSTAT

Receive the

PPOLL

status

PRINT PPSTAT

and print it.

1 2 ... 140 141 142 143 144 145 146 147 148 149 150 ... 280 281

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Measurement-computing Analyzer488 Manuale Utente Pagina 145