Int 14 Fn 24  - Multidos Plus - Set Monitor Mode                           [S]

   AH = 24h
   AL = port status storage
       00h single status for entire receive buffer
       01h separate status kept for each byte in receive buffer
   DX = port number

Return: AH = status
       00h successful
       3Ah invalid status storage specified
       41h no such port
       64h monitor mode already active

Note:  in monitor mode, MultiDOS redirects all BIOS video output to a serial
     port

See Also: AH=20h"MultiDOS",AH=25h