Int 14H [PC] [AT] [PS/2] Function 01H Write character to communications port

Writes a character to the specified serial communications port, returning the current status of the port.

Call with:

AH = 01H

AL = character

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

Returns:

If function successful

AH bit 7 = 0

AH bits = port status

0—6

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

AL = character (unchanged)

If function unsuccessful (timed-out)

AH bit 7 = 1

AL = character (unchanged)