INT 14 - MultiDOS Plus IODRV - GET PORT STATUS
        AH = 07h
Return: CL = modem status (see AH=03h)
        CH = character at head of input queue (if any)
        DX = number of characters in input queue
Note:   the port number is stored at offset BEh in the Task Control Block
SeeAlso: AH=05h"MultiDOS",AH=08h"MultiDOS",AH=09h"MultiDOS"