Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

                                                      ◄Up► ◄Next► ◄Previous►
────────────────────────────────────────────────────────────────────────────
 
#define INCL_DOSDEVIOCTL
 
USHORT DosDevIOCtl(pfCommErr, 0L, 0x004B, 0x0001, hDevice)
PUSHORT pfCommErr;    /* pointer to variable for error value */
HFILE hDevice;        /* device handle                       */
 
The ASYNC_SETBREAKON function turns on the break character. The device
driver generates the break signal immediately. It is not considered an error
if the device driver is already generating a break signal. The device driver
does not wait for the transmit hardware to become empty. However, more data
will not be given to the transmit hardware until the break is turned off.
The break signal will always be transmitted, regardless of whether the
device driver is or is not transmitting characters due to other reasons.
 
Parameter  Description
────────────────────────────────────────────────────────────────────────────
 
pfCommErr  Points to the variable that receives the communication status of
           the device. This variable can be a combination of the following
           values:
 
           Value                Meaning
           ─────────────────────────────────────────────────────────────────
           RX_QUE_OVERRUN       Receive queue overrun. There is no room in
                                the device-driver receive queue to put a
                                character read in from the receive
                                hardware.
 
           RX_HARDWARE_OVERRUN  Receive hardware overrun. A character
                                arrived before the previous character was
                                completely read. The previous character is
                                lost.
 
           PARITY_ERROR         The hardware detected a parity error.
 
           FRAMING_ERROR        The hardware detected a framing error.
 
           The function sets the variable to zero if it encounters an
           error.
 
hDevice    Identifies the serial device that receives the device-control
           function. The handle must have been created previously by using
           the DosOpen function.
 
Return Value
 
The return value is zero if the function is successful or an error value if
an error occurs.
 
Comments
 
Closing the device turns off the break character if there are no outstanding
open device handles.
 
See Also
 
DosOpen, ASYNC_SETBREAKOFF
 
                                      ♦