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Synopsis:
    #include <bios.h>
    unsigned short _bios_serialcom( unsigned service,
                                    unsigned serial_port,
                                    unsigned data );

Description:
    The _bios_serialcom function uses INT 0x14 to provide serial
    communications services to the serial port specified by serial_port.  0
    represents COM1, 1 represents COM2, etc.  The values for service are:

    Value     Meaning

_COM_INIT
    Initializes the serial port to the parameters specified in data.

_COM_SEND
    Transmits the low-order byte of data to the serial port.

_COM_RECEIVE
    Reads an input character from the serial port.

_COM_STATUS
    Returns the current status of the serial port.

    The value passed in data for the  _COM_INIT service can be built using
    the appropriate combination of the following values:

    Value     Meaning

_COM_110
    110 baud

_COM_150
    150 baud

_COM_300
    300 baud

_COM_600
    600 baud

_COM_1200
    1200 baud

_COM_2400
    2400 baud

_COM_4800
    4800 baud

_COM_9600
    9600 baud

_COM_NOPARITY
    No parity

_COM_EVENPARITY
    Even parity

_COM_ODDPARITY
    Odd parity

_COM_CHR7
    7 data bits

_COM_CHR8
    8 data bits

_COM_STOP1
    1 stop bit

_COM_STOP2
    2 stop bits


Returns:
    The _bios_serialcom function returns a 16-bit value with the high-order
    byte containing status information defined as follows:

    Bit     Meaning

bit 15 (0x8000)
    Timed out

bit 14 (0x4000)
    Transmit shift register empty

bit 13 (0x2000)
    Transmit holding register empty

bit 12 (0x1000)
    Break detected

bit 11 (0x0800)
    Framing error

bit 10 (0x0400)
    Parity error

bit 9 (0x0200)
    Overrun error

bit 8 (0x0100)
    Data ready

    The low-order byte of the return value depends on the value of the
    service argument.

    When service is _COM_SEND, bit 15 will be set if the data could not be
    sent.  If bit 15 is clear, the return value equals the byte sent.

    When service is _COM_RECEIVE, the byte read will be returned in the
    low-order byte if there was no error.  If there was an error, at least
    one of the high-order status bits will be set.

    When service is _COM_INIT or _COM_STATUS the low-order bits are defined
    as follows:

    Bit     Meaning

bit 0 (0x01)
    Clear to send (CTS) changed

bit 1 (0x02)
    Data set ready changed

bit 2 (0x04)
    Trailing-edge ring detector

bit 3 (0x08)
    Receive line signal detector changed

bit 4 (0x10)
    Clear to send

bit 5 (0x20)
    Data-set ready

bit 6 (0x40)
    Ring indicator

bit 7 (0x80)
    Receive-line signal detected


Example:
    #include <stdio.h>
    #include <bios.h>

    void main()
      {
        unsigned short status;

        status = _bios_serialcom( _COM_STATUS, 1, 0 );
        printf( "Serial status: 0x%2.2X\n", status );
      }

Classification:
    BIOS

Systems:
    DOS, Windows, Win386