Int 14 Fn 0A  - Digiboard Digichannel PC/x* - Input Queue Check            [S]

   AH = 0Ah
   DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)

Return: AX = number of characters available in buffer

Note:  this function is also supported by the PC-MOS/386 v5.01 $serial.sys

See Also: AH=09h"Digiboard",AH=0Dh"Digiboard"