Omega OMB-PER-488/W95, User Manual

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Personal488 User's Manual For Windows 95 and Windows NT API Command Reference 83
OnEvent
Syntax
INT WINAPI OnEvent(DevHandleT devHandle, HWND hWnd, OpaqueP
lParam);
devHandle
refers to either an interface or an external device.
hWnd is the window handle to receive the event notification.
lParam value will be passed in the notification message.
Returns
-1 if error
Mode
Any
Bus States
None
Example
ieee = OpenName (“ieee”);
OnEvent (ieee, hWnd, (OpaqueP) 12345678L);
Arm (ieee, acSRQ | acError);
break;
See Also
OnEventVDM, Arm, Disarm
The
OnEvent
command causes the event handling mechanism to issue a message upon occurrence of
an
Arm
ed event. The message will have a type of
WM_IEEE488EVENT
, whose value is retrieved via:
RegisterWindowMessage ((LPSTR) “WM_IEEE488EVENT”);
The associated
wParam
is an event mask indicating which
Arm
ed event(s) caused the notification, and
the
lParam
is the value passed to
OnEvent
. Note that although there is a macro for
WM_IEEE488EVENT
in the header file for each language, this macro resolves to a function call and
therefore cannot be used as a case label. The preferred implementation is to include a default case in
the message handling case statement and directly compare the message ID with
WM_IEEE488EVENT
.
The following is a full example of a program using the
OnEvent
function:
LONG FAR WINAPI export
WndProc(HWND hWnd, unsigned iMessage, WORD wParam, LONG lParam);
{
HANDLE
ieee;
switch (iMessage)
{
case WM_CREATE:
ieee = OpenName (“ieee”);
OnEvent (ieee, hWnd, (OpaqueP) 12345678L);
Arm (ieee, acSRQ | acError);
break;
default:
if (iMessage == WM_IEEE488EVENT) {
char buff [80];
wsprintf (buff, “Condition = %04X,
Param = %081X”,wParam, lParam);
MessageBox (hWnd, (LPSTR) buff,
(LPSTR) “Event Noted”, MB OK);
return TRUE;
}
}
}