The MON51 debugger can run equally from internal or external ROM.

BlueEarth, LLC has been shipping microcontroller products for 12 years, and several models, including the Micro-485 come with the original Franklin Monitor-51, along with a floating-point BASIC interpreter. The standard configuration includes an 80C51FA CPU (no internal code memory) with BASIC & MON-51 in EPROM. However, some customers order configurations with an 87C51FB with BASIC and MON-51 in the CPU ROM. The product works identically in both cases. The only difference is the EA jumper position.

-- Tom Bachmann