INT 14 - Digiboard DigiCHANNEL PC/X* - GET POINTER TO CH_KEY_RDY FLAG
AH = 0Dh
DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)
Return: ES:BX -> CH_KEY_RDY flag

Values for CH_KEY_RDY flag:
00h    receive buffer empty
FFh    characters available

See also: 140A

140D - Digiboard DigiCHANNEL PC/X* - GET POINTER TO CH_KEY_RDY FLAG