Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 356)

III. COMMAND REFERENCES - 15. Command References 15B. Driver488/SUB, W31, W95, & WNT
Personal488 User’s Manual, Rev. 3.0 III-341
PassControl
SYNTAX int pascal PassControl(DevHandleT devHandle);
devHandle refers to an external device to which control is passed.
RETURNS -1 if error
MODE CA
BUS STATES ATN
•UNL, MLA, TAG, UNL, TCT, *ATN
SEE ALSO Abort, Reset, SendCmd
EXAMPLE errorcode = PassControl(scope);
The PassControl command allows Driver488 to give control to another controller on the bus. After
passing control, Driver488 enters the Peripheral mode. If Driver488 was the System Controller, then it
remains the System Controller, but it is no longer the Active Controller. The Controller now has
command of the bus until it passes control to another device or back to Driver488. The System
Controller can regain control of the bus at any time by issuing an
Abort command.
PPoll
SYNTAX int pascal 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
SEE ALSO PPollConfig, PPollUnconfig, PPollDisable, SPoll
EXAMPLE errorcode = PPoll(ieee);
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 Parallel Poll capabilities are
supported.
PPollConfig
SYNTAX int pascal PPollConfig(DevHandleT devHandle, int ppresponse);
devHandle refers to either an interface or an external device to configure for the
Parallel Poll.
ppresponse is the decimal equivalent of the four binary bits S , P2 , P1 , and P0
where S is the Sense bit, and P2 , P1 , and P0 assign the DIO bus data line used
for the response.
RETURNS -1 if error
MODE CA
BUS STATES ATN
•UNL, MTA, LAG, PPC