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IOCTL_SERIAL_LSRMST_INSERT info Overview Group

The IOCTL_SERIAL_LSRMST_INSERT DeviceIoControl operation enables or disables the placement of line status and modem status values into the regular data stream that an application acquires through the ReadFile function.

When this line-status and modem-status data placement mode is enabled, status values are preceded in the data stream by an escape character. The user-definable escape character is set by the IOCTL_SERIAL_LSRMST_INSERT operation. Status values consist of 1 to 3 BYTEs. See the Remarks section below for status value details.

dwIoControlCode = IOCTL_SERIAL_LSRMST_INSERT;     // operation code 

lpInBuffer;         // address of input buffer 

nInBufferSize;      // size of input buffer 

lpOutBuffer = NULL; // address of output buffer; not used; must be NULL 

nOutBufferSize = 0; // size of output buffer; not used; must be zero 

lpBytesReturned;    // address of actual bytes of output

Parameters

lpInBuffer

Points to a buffer that contains a single BYTE.

If the BYTE is a nonzero value, it is the desired line-status and modem-status value escape character. The operation will turn the LSRMST_INSERT line-status and modem-status data placement mode on.

If the BYTE is zero, the operation will turn the LSRMST_INSERT line-status and modem-status data placement mode off.

The escape character can not be the XON or XOFF character.

nInBufferSize

Specifies the size, in bytes, of the buffer pointed to by lpInBuffer. For this operation, this value should be 1.

lpOutBuffer

Points to an output buffer. Not used with this operation. Set to NULL.

nOutBufferSize

Specifies the size, in bytes, of the buffer pointed to by lpOutBuffer. Not used with this operation. Set to zero.

lpBytesReturned

Points to a DWORD that receives the actual size, in bytes, of the data stored into lpOutBuffer.

Return Values

If the operation succeeds, DeviceIoControl returns a nonzero value.

If the operation fails, DeviceIoControl returns zero. To get extended error information, call GetLastError.

Remarks

Note that an application that uses this scheme must examine each character in the data stream to determine the presence of modem-status or line-status data.

The following values follow the designated escape character in the data stream if the LSRMST_INSERT mode has been turned on :

Value

Meaning

SERIAL_LSRMST_ESCAPE

Indicates the reception of the escape character itself into the data stream.

SERIAL_LSRMST_LSR_DATA

Indicates that a line status change occurred, and data was available in the receive hardware buffer. Following this BYTE is a BYTE value of the line status register is the BYTE present in the receive hardware buffer when the line status change was processed.

SERIAL_LSRMST_LSR_NODATA

Indicates that a line status change occurred, but no data was available in the receive hardware buffer.

SERIAL_LSRMST_MST

Indicates that a modem status change occurred. Following this BYTE is a BYTE that is the value of the modem status register when the modem status change was processed.

Value	Meaning
SERIAL_LSRMST_ESCAPE	Indicates the reception of the escape character itself into the data stream.
SERIAL_LSRMST_LSR_DATA	Indicates that a line status change occurred, and data was available in the receive hardware buffer. Following this BYTE is a BYTE value of the line status register is the BYTE present in the receive hardware buffer when the line status change was processed.
SERIAL_LSRMST_LSR_NODATA	Indicates that a line status change occurred, but no data was available in the receive hardware buffer.
SERIAL_LSRMST_MST	Indicates that a modem status change occurred. Following this BYTE is a BYTE that is the value of the modem status register when the modem status change was processed.

IOCTL_SERIAL_LSRMST_INSERT info Overview Group

Parameters

Return Values

Remarks

See Also