INT 14 - Digiboard DigiCHANNEL PC/X* - SPECIAL CHARACTER INTERRUPT
AH = 19h
BL = flag
00h disable special character interrupt
FFh enable interrupt
DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)
Return: AH = status
00h successful
FFh failed

See also: 141A

1419 - Digiboard DigiCHANNEL PC/X* - SPECIAL CHARACTER INTERRUPT