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INT 14 - SERIAL I/O - INITIALIZE USART
        AH = 00h
        AL = initializing parameters
            7 - 6 - 5      4 - 3     2    1 - 0
            -BAUD RATE-    PARITY   STOP   WORD
                                    BITS  LENGTH
            000  110 bd    00 none  0: 1   00: 5
            001  150 bd    01 odd   1: 2   01: 6
            010  300 bd    11 even         10: 7
            011  600 bd                    11: 8
            100 1200 bd
            101 2400 bd
            110 4800 bd
            111 9600 bd (4800 on PCjr)
        DX = port number (0-3)
Return: AH = RS-232 status code bits
            0: data ready
            1: overrun error
            2: parity error
            3: framing error
            4: break detected
            5: transmission buffer register empty
            6: transmission shift register empty
            7: time out--if set, other bits invalid
        AL = modem status bits
            0: delta Clear-To-Send
            1: delta Data-Set-Ready
            2: trailing edge of ring detected
            3: change in receive line signal detected
            4: Clear-To-Send
            5: Data-Set-Ready
            6: ring detected
            7: receive line signal detected
SeeAlso: AH=05h,AH=82h,AH=8Ch