Int 14 Fn 0F - Digiboard Digichannel Pc/x* - Read String [S]
AH = 0Fh
CX = number of characters to read
ES:BX -> buffer
DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)
Return: AX = number of characters read
ZF clear if successful
ZF set on error (line status or wrong number of characters)
See Also: AH=0Eh"Digiboard"