Extract Microcontroller Code include a series of different methods and all of these methods can be separated into three kinds, first is the invasive microcontroller unlocking, second is semi-invasive microcontroller code extraction, third is non-invasive microcontroller code extraction.

Software stimulation extraction method is one of the most effective ways for non-invasive chip code extraction analysis method. We can add Laser impulse to P type transistor grid where is 10 microns area, microcontroller attacker can assume that the turning around will occur when the output voltage is higher than the input voltage with 1 logic value, It is much higher than normal reversor threshold value voltage, but with the absence of internal precise threshold value voltage information from microcontroller internally.

As we checked before, the stimulation result is same, and with great area on the microcontroller will response to the laser’s energy. It can turn the reversor around completely without the locked effect when extract mcu at89ls51 firmware. This kind of difference could be bigger in the shorter wavelength laser. It is because the silicon will absorb the short wavelength laser energy and cause the increasing quantity of ion pairs beneath the transistor grid. From one side, it will improve the modification ability in the channel, from other side, it decrease the current from N type transistor and make the parasite structure become more difficult to turn around.