Int 14h, 04h            Initialize Extended Serial Port                  PS/2

    Sets up the PS/2 Serial Port parameters.

        Entry   AH = 04h
                AL = Break:
                     | 00  No Break
                     | 01  Break
                BH = Parity:
                     | 00  None
                     | 01  Odd
                     | 02  Even
                     | 03  Stick parity odd
                     | 04  Stick parity even
                BL = Stop Bits:
                     | 00  1 stop bit
                     | 01  2 for word length 6, 7, or 8
                           1½ for word length 5
                CH = Word Length:
                     | 00  5 bits
                     | 01  6 bits
                     | 02  7 bits
                     | 03  8 bits
                CL = Baud Rate:
                     | 00  110 baud
                     | 01  150 baud
                     | 02  300 baud
                     | 03  600 baud
                     | 04  1200 baud
                     | 04  2400 baud
                     | 04  4800 baud
                     | 04  9600 baud
                     | 04  19,200 baud
                DX = Serial Port to Configure

        Return  AL = Modem Status (See Service 03h)
                AH = Line Status (See Service 03h)

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    This service configures the PS/2 serial ports. It is recommended
    over service 00h.

    This is the way you can select the baud rate, word length, parity
    settings, and stop bits that are required in serial
    communications. You only need to code the settings you want as
    shown above and call this service. The PS/2 supports baud rates up
    to 19,200.


    Note
    This service returns modem and line status, as does Service 03h.
    (See Service 03h for details.) See Services 01h and 02h for
    information on sending and receiving characters.