SetCommState

The SetCommState function configures a communications device according to the specifications in a device-control block (a DCB structure). The function reinitializes all hardware and control settings, but it does not empty output or input queues.

BOOL SetCommState(
  HANDLE hFile,  // handle to communications device
  LPDCB lpDCB    // device-control block
);

Parameters

hFile

[in] Handle to the communications device. The CreateFile function returns this handle.

lpDCB

[in] Pointer to a DCB structure that contains the configuration information for the specified communications device.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

The SetCommState function uses a DCB structure to specify the desired configuration. The GetCommState function returns the current configuration.

To set only a few members of the DCB structure, you should modify a DCB structure that has been filled in by a call to GetCommState. This ensures that the other members of the DCB structure have appropriate values.

The SetCommState function fails if the XonChar member of the DCB structure is equal to the XoffChar member.

When SetCommState is used to configure the 8250, the following restrictions apply to the values for the DCB structure's ByteSize and StopBits members:

The number of data bits must be 5 to 8 bits.

Requirements

  Windows NT/2000: Requires Windows NT 3.1 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Winbase.h; include Windows.h.
  Library: Use Kernel32.lib.

See Also

Communications Overview, Communication Functions, BuildCommDCB, CreateFile, DCB, GetCommState