Ppollconfig – Measurement Computing Personal488 rev.3.0 User Manual
Page 109
Personal488 for Windows 95/98/Me/NT/2000
04-10-01
API Reference 6-41
PPollConfig
Syntax
INT WINAPI PPollConfig(DevHandleT devHandle,BYTE 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
Bus States
ATN
•UNL, MTA, LAG, PPC
Example
errorcode =
PPollConfig
(dmm,0x0D);
Configure device
DMM
to assert
DIO6
when it desires service
(
ist
= 1) and it is Parallel Polled (0x0D = &H0D = 1101
binary;
S
=1,
P2
=1,
P1
=0,
P0
=1; 101 binary = 5 decimal =
DIO6
).
See Also
PPoll, PPollUnconfig, PPollDisable
The
PPollConfig
command configures the Parallel Poll response of a specified bus device. Not all
devices support Parallel Polling and, among those that do, not all support the software control of their
Parallel Poll response. Some devices are configured by internal switches.
The Parallel Poll response is set by a four-bit binary number response:
S
,
P2
,
P1
, and
P0
. The most
significant bit of response is the Sense (
S
) bit. The Sense bit is used to determine when the device will
assert its Parallel Poll response. Each bus device has an internal individual status (
ist
). The Parallel Poll
response is asserted when this
ist
equals the Sense bit value
S
. The
ist
is normally a logic
1
when the
device requires attention, so the
S
bit should normally also be a logic
1
. If the
S
bit is
0
, then the device
asserts its Parallel Poll response when its
ist
is a logic
0
. That is, it does not require attention. However,
the meaning of
ist
can vary between devices, so refer to your IEEE 488 bus device documentation. The
remaining 3 bits of response:
P2
,
P1
, and
P0
, specify which
DIO
bus data line is asserted by the device in
response to a Parallel Poll. These bits form a binary number with a decimal value from
0
through
7
,
specifying data lines
DIO1
through
DIO8
, respectively.