INT 14 - Digiboard DigiCHANNEL PC/X* - ALTERNATE STATUS CHECK
        AH = 08h
        DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)
Return: AH = RS232 status bits (see AH=03h)
        ZF set if no characters queued
        ZF clear if character available
            AL = next character
SeeAlso: AH=09h"Digiboard"