Int 14 Fn 18  - Digiboard Digichannel PC/x* - Send BIOS Command            [S]

   AH = 18h
   ES:BX -> 16-byte command string
   DX = port number (00h-03h) (04h-43h for XAPCM232.SYS)

Return: AH = status
       00h successful
       80h timeout
   AL = mailbox status
       00h no errors
       8Xh BIOS error
   ES:BX buffer filled in with mailbox string
   ZF clear if no errors
   ZF set if either status byte contains an error code

See Also: AH=16h"Digiboard"