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#define INCL_DOSDEVIOCTL
 
USHORT DosDevIOCtl(0L, 0L, 0x0047, 0x0001, hDevice)
HFILE hDevice;    /* device handle */
 
The ASYNC_STOPTRANSMIT function stops the device from transmitting. This
function stops data transmission by preventing the device driver from
sending additional data to the transmit hardware. This function is similar
to the device receiving the XOFF character.
 
Parameter  Description
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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
 
If automatic-transmission control is enabled, this request causes the device
driver to behave exactly as if it received the XOFF character. Transmission
can be resumed if an XON character is received by the device driver, if an
ASYNC_STARTTRANSMIT (0x0001,0x0048) function is received, or if the device
driver is told to disable automatic-transmission control and in the previous
state automatic-transmission control was enabled.
 
If automatic-transmission control is disabled, the ASYNC_STARTTRANSMIT
function (0x0001,0x0048) must be called for transmission to resume. If,
after this request is received, the device driver is told to enable
automatic-transmission control, transmission is still disabled. It can be
re-enabled by any of the scenarios discussed above.
 
There still may be other reasons why transmission may be disabled. For more
information, see the ASYNC_GETCOMMSTATUS  function (0x0001,0x0064).
 
See Also
 
DosOpen, ASYNC_GETCOMMSTATUS, ASYNC_STARTTRANSMIT
 
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