Omega OMB-PER-488/W95, User Manual

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98 API Command Reference Personal488 User's Manual For Windows95 and Windows NT
Request
Syntax
INT WINAPI Request(DevHandleT devHandle, BYTE spstatus);
devHandle refers to either an interface or an external device. If devHandle refers to an
external device, the
Request
command acts on the hardware interface to which the
external device is attached.
spstatus is the Service Request status in the range 0 to 255 .
Returns
-1 if error
Mode
*CA
Bus States
SRQ (if rsv is set)
*SRQ (if rsv is not set)
Examples
errorcode = Request(ieee,0); Clears SRQ and Serial Poll Response.
errorcode =
Request(ieee,64+2+4);
Generates an SRQ (decimal 64) with DIO2
(decimal 2) and
DIO3
(decimal 4) set in
the Serial Poll Response.
See Also
Status, ControlLine
In Peripheral mode, Driver488 is able to request service from the Active Controller by asserting the
Service Request (
SRQ
) bus signal. The
Request
command sets or clears the Serial Poll status
(including Service Request) of Driver488.
Request
takes a numeric argument in the decimal range
0
to
255
(hex range
&H0
to
&HFF
) that is used to set the Serial Poll status. When Driver488 is Serial
Polled by the Controller, it returns this byte on the
DIO
data lines.
The data lines are numbered
DIO8
through
DIO1
.
DIO8
is the most significant line and corresponds to
a decimal value of
128
(hex
&H80
).
DIO7
is the next most significant line and corresponds to a
decimal value of
64
(hex
&H40
).
DIO7
has a special meaning: It is the
Request for Service
(
rsv
) bit. If
rsv
is set, then Driver488 asserts the Service Request (
SRQ
) bus signal. If
DIO7
is clear (a logic
0
),
then Driver488 does not assert SRQ. When Driver488 is Serial Polled, all eight bits of the Serial Poll
status are returned to the Controller. The
rsv
bit is cleared when Driver488 is Serial Polled by the
Controller. This causes Driver488 to stop asserting
SRQ
.