INT 14 - SERIAL - INITIALIZE PORT
        AH = 00h
        AL = port parameters
            bits 7-5 data rate (110,150,300,600,1200,2400,4800,9600 bps)
            bits 4-3 parity (00 or 10 = none, 01 = odd, 11 = even)
            bit 2    stop bits (set = 2, clear = 1)
            bits 1-0 data bits (00 = 5, 01 = 6, 10 = 7, 11 = 8)
        DX = port number (00h-03h) (04h-43h for Digiboard XAPCM232.SYS)
Return: AH = line status (see AH=03h)
            FFh if error on Digiboard XAPCM232.SYS
        AL = modem status (see AH=03h)
Notes:  default handler is at F000h:E739h in IBM PC and 100% compatible BIOSes
        since the PCjr supports a maximum of 4800 bps, attempting to set 9600
          bps will result in 4800 bps
SeeAlso: AH=04h"MultiDOS",AH=05h"SERIAL",AH=81h"COMM-DRV"