INT 14 - BIOS Asynchronous Communications Services

	For more information, see the following topics:

	INT 14,0  Initialize serial port parameters
	INT 14,1  Send character in AL
	INT 14,2  Receive character in AL
	INT 14,3  Get Serial port status
	INT 14,4  Extended initialize  (PS/2)
	INT 14,5  Extended communication port control (PS/2)


	- all functions have:
	  AH = function number
	  AL = character to send or receive
	  DX = zero based RS232 card number
	- all registers are preserved except AX
	- these functions use hardware flow control
	- used by DOS MODE to redirect LPTx output to a serial device
	- see individual functions for more data

BIOS Asynchronous Communications Services (Status)

		|7|6|5|4|3|2|1|0|  AL  modem status
		 | | | | | | | `---- clear to send status changed
		 | | | | | | `----- data set ready status changed
		 | | | | | `------ trailing edge ring indicator
		 | | | | `------- receive line signal changed
		 | | | `-------- clear to send
		 | | `--------- data set ready
		 | `---------- ring indicator
		 `----------- receive line signal detected

		|7|6|5|4|3|2|1|0|  AH  port status
		 | | | | | | | `---- data ready
		 | | | | | | `----- overrun error
		 | | | | | `------ parity error
		 | | | | `------- framing error
		 | | | `-------- break detect
		 | | `--------- transmit holding register empty
		 | `---------- transmit shift register empty
		 `----------- time out (N/A for functions 1 and 2)