Siemens M20 Terminal Technical Description page 181

Siemens Information and Communication Products
Comments If an application specifies -1 for the cbWriteNotify parameter, the WM_COMMNOTIFY message
is sent to the specified window for CN_EVENT and CN_TRANSMIT notifications but not for
CN_RECEIVE notifications. If -1 is specified for the cbOutQueue parameter, CN_EVENT and
CN_RECEIVE notifications are sent but CN_TRANSMIT notifications are not sent.
If a timeout occurs before as many bytes as specified by the cbWriteNotify parameter are written
to the input queue, a WM_COMMNOTIFY message is sent with the CN_RECEIVE flag set.
When this occurs, another message will not be sent until the number of bytes in the input queue
falls below the number specified in the cbWriteNotify parameter. Similarly, a
WM_COMMNOTIFY message in which the CN_RECEIVE flag is set is sent only when the out-
put queue is larger than the number of bytes specified in the cbOutQueue parameter.
The Windows 3.0 version of COMM.DRV does not support this function.
See also WM_COMMNOTIFY
8.4.2.5 LONG EscapeCommFunction(idComDev, nFunction)
int idComDev;
int nFunction;
The EscapeCommFunction function directs the specified communications device to carry out an extended function.
LONG EscapeCommFunction(idComDev, nFunction)
Parameter Description
idComDev Specifies the communications device that will carry out the extended function. The OpenComm
function returns this value.
nFunction Specifies the function code of the extended function. It can be one of the following values:
Value meaning
CLRDTR clears the DTR (data terminal ready) signal.
CLRRTS clears the RTS (request to send) signal.
GETMAXCOM returns the maximum COM port identifier supported by the system. This value
ranges from 0x00 to 0x7F, such that 0x00 corresponds to COM1, 0x01 to COM2, 0x02 to COM3,
and so on.
GETMAXLPT returns the maximum LPT port identifier supported by the system. This value ran-
ges from 0x80 to 0xFF, such that 0x80 corresponds to LPT1, 0x81 to LPT2, 0x82 to LPT3, and so
on.
RESETDEV resets the printer device if the idComDev parameter specifies an LPT port. No
function is performed if idComDev specifies a COM port.
SETDTR sends the DTR (data terminal ready) signal.
SETRTS sends the RTS (request to send) signal
SETXOFF causes transmission to act as if an XOFF character has been received.
SETXON causes transmission to act as if an XON character has been received.
Return value 0 if the function is successful.
Otherwise < 0
Example None
Comments None
See also None
Version 8 dated 15.03.00
/* identifies communications device
/* code of extended function
*/
*/
Application notes
A
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