MCU Reading is a complicate process which have several different methods to process it and during which frozen the MCU inside it to keep the data as long as it can become prevail methods. And we have done a series of experiment to prove the availability of this method.
The data remanence time length can be longer if the power consumption of MCU can be lower when reading it. The data remanence time length could be shorter if the power supply pin which connect to the ground than floating. Once the SRAM chip of MCU start to lose data, it will lose it very soon. After the comparison with NEC4364C-15 and NEC4364C-15L, which has a low voltage version. We can conclude that the MCU with lower voltage can have longer time length of data remanence in any temperature compare with the MCU with higher voltage when reading it. But the situation become converse in the below MCUs, HY6264A-10LL and HY62256BL-70, the one in front of it is a extremely low voltage version. But the second one even though has a higher voltage but the time length of data romanence before lost of MCU reading is longer due to the application of smaller transistors and lower power consumption.
We test and record the modern SRAM MCU sample’s data remanence time length before reading, it is a temperature function. It is opposite to the common sense, there are several MCU chips could be quite dangers since their data remanence in the minus 20 degrees are all very short and for those MCUs which can keep 80% of data for over 1 minute is very difference. Some of them can be reading MCU only after below minus 50 degrees and some of them just need to have normal condition.
There is something beyond our expectation is the data remanence of MCU can be different not only from the different MCU type but also the same type with different manufacturer code can have different data remanence when cracking MCU. So we conclude the data remanence is not include in the quality standard of MCU production. For the same MCU, lower power consumption can have longer data remanence when extract microcontroller heximal. As a result of that, the erasable memorizer must be used for the MCU when the processor can be copied and alter.
