Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 348)

III. COMMAND REFERENCES - 15. Command References 15B. Driver488/SUB, W31, W95, & WNT
Personal488 User’s Manual, Rev. 3.0 III-333
determine the state of Driver488 and take appropriate action. OnEvent is most often used to respond
to Service Requests ( SRQ ).
OnEvent
Driver488/W31 (C only) and Driver488/W95 only
SYNTAX int pascal 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
SEE ALSO Arm, Disarm
BUS STATES None
EXAMPLE ieee = OpenName (“ieee”);
OnEvent (ieee, hWnd, (OpaqueP) 12345678L);
Arm (ieee, acSRQ | acError);
break;
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 PASCAL 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;
}
}
}