How to Extract MCU Code is a task for engineers who wants to make IC clone from exisiting microcontroller memory reading;
The principle of this method is monitor simulation characteristic of all the power supply and interface connection during the standard operation under high resolution, and copy MCU firmware by monitoring its electromagnetic radiation.
Because MCU is an active electronic component, when it operate different orders, corresponding power supply consumption will alter accordingly. Then use special electronic measurement device and mathematic statistical method to analyze and detect these changes, can extract code embedded inside microprocessor.
Currently RF programmer can read program of old MCU is base upon this principle.