Int 15 Fn F200  - Tandon Memory Mapper - Tandon Mapper Hardware Initialis  [m]

   AX = F200h
   CX = 454Dh

Return: CF clear if hardware already initialised
       BX = upper RAM areas in use
       bit 0: C000-C3FF
       bit 1: C400-C7FF
       ...
       bit 11: EC00-EFFF
   CF set if hardware not initialised yet