Int 14H [PC] [AT] [PS/2] Function 00H Initialize communications port

Initializes a serial communications port to a desired baud rate, parity, word length, and number of stop bits.

Call with:

AH = 00H

AL = initialization parameter (see Notes)

DX = communications port number (0 = COM1, 1 = COM2, etc.)

Returns:

AH = port status

Bit Significance (if set)

0 receive data ready

1 overrun error detected

2 parity error detected

3 framing error detected

4 break detected

5 transmit holding register empty

6 transmit shift register empty

7 timed-out

AL = modem status

Bit Significance (if set)

0 change in clear-to-send status

1 change in data-set-ready status

2 trailing edge ring indicator

3 change in receive line signal detect

4 clear-to-send

5 data-set-ready

6 ring indicator

7 receive line signal detect

Notes:

The initialization parameter byte is defined as follows:

7 6 5 4 3 2 1 0 Baud rate Parity Stop bits Word length 000 = 110 X0 = none 0 = 1 bit 10 = 7 bits 001 = 150 01 = odd 1 = 2 bits 11 = 8 bits 010 = 300 11 = even 011 = 600 100 = 1200 101 = 2400 110 = 4800 111 = 9600

To initialize the serial port for data rates greater than 9600 baud on PS/2 machines, see Int 14H Functions 04H and 05H.