Expects: AH    00H
AL    initialization bit flags (see below)
DX    COMM port number (0 to 3)
                                                                  
Returns: AH    line status        see BIOS COM status codes
AL    modem status   
                                                                  
Info: Sets the speed, word length, etc for the specified COM port.

AL on entry, AL specifies the COM settings:

 7 6 5 4 3 2 1 0 
 baud  par s len 
                  bit  mask
                 0-1: 03H  word length: 10=7 bits; 11=8 bits
                 2: 04H  stop bits:  0=1; 1=2;
               3-4: 18H parity code: x0=none; 01=odd; 11=even
               5-7: e0H baud rate  000=110; 100=1200
001=150; 101=2400
010=300; 110=4800
011=600; 111=9600

Notes: BIOS does not support speeds beyond 9600 baud, even though most
hardware is capable of much higher rates.

- -

INT 14H 00H: Initialize Asynchronous Communication Port