Function 04h	Extended Initialize				(PC Convertible)
entry   AH      04h 
	AL      break status 
		01h     if break 
		00h     if no break 
	BH      parity 
		00h     no parity 
		01h     odd parity 
		02h     even parity 
		03h     stick parity odd 
		04h     stick parity even 
	BL      number of stop bits 
		00h     one stop bit 
		01h     2 stop bits (1  if 5 bit word length) 
	CH      word length 
		00h     5 bits 
		01h     6 bits 
		02h     7 bits 
		03h     8 bits 
	CL      baud rate 
		00h     110 
		01h     150 
		02h     300 
		03h     600 
		04h     1200 
		05h     2400 
		06h     4800 
		07h     9600 
		08h     19200 
return  AL      modem status 
	AH      line control status