INT 14 - Digiboard DigiCHANNEL PC/X* - CHANGE PROTOCOL
AH = 05h
AL = protocol
bits 7-4 unused
bit 3: RTS/CTS
bit 2: DSR
bits 1,0: XON/XOFF
BH = new XOFF character (00h = current)
BL = new XON character (00h = current)
DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)
Return: AH = status
00h successful
FFh error

See also: 1404

1405 - Digiboard DigiCHANNEL PC/X* - CHANGE PROTOCOL