INT 14 - Digiboard DigiCHANNEL PC/X - SPECIAL CHARACTER FLAG/COUNTER
AH = 1Ah
BX = subfunction
00h return pointer to special character flag byte
01h return pointer to special character counter word
DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)
Return: ES:BX -> special character flag or counter
Notes:  flag is FFh if one or more special characters are in the receive
buffer; it is 00h and the counter is invalid if no special characters
are in the receive buffer
counter (if valid) contains the number of characters in the receive
buffer up to and including the last-received special character


141A - Digiboard DigiCHANNEL PC/X - SPECIAL CHARACTER FLAG/COUNTER