51 MCU encryption and decryption

　　After completing the three-level encryption, the 51-type MCU uses the method of burning the encryption lock bit (breaking through the silicon chip in the chip) without damaging other parts and occupying any resources of the MCU. After the encryption lock bit is burned, it no longer has the erasing feature. Once encrypted in OTP mode, the encryption bit in the MCU chip and the data in the program memory cannot be erased again.

　　After OTP encryption, when reading and testing through the programmer, it will prompt: Some pins have poor contact-----broken pins.

　　For example: burning out the EA pin of pin 31 of 89C51, burning out the data line of 89C51 and 89C2051, and burning out the data clock line of PIC series chips, etc.

　　This encryption method will cause certain difficulties for some methods of decrypting data bits through microcontrollers.

　　ATMEL 89C series 51 single chip microcomputer features:

　　1. Contains Flash memory

　　Therefore, the program can be easily modified during the system development process, which greatly shortens the system development cycle. At the same time, during the system operation, some data information can be effectively saved, and even if the external power supply is damaged, it will not affect the preservation of information.

　　2. Compatible with 80C51 socket

　　The pins of the 89C series microcontrollers are the same as those of the 80C51, so when the 89C series microcontrollers are used to replace the 80C51, they can be directly replaced. At this time, no matter whether the product is 40-pin or 44-pin, just replace the 80C51 microcontroller with the 89C series microcontroller with the same pins.

　　3. Static clock mode

　　The 89C series microcontrollers use a static clock mode, so they can save energy, which is very useful for reducing the power consumption of portable products.

　　4. No waste even if programming is wrong

　　General OTP products will become waste if they are programmed incorrectly. However, the 89C series MCU uses Flash memory inside, so after incorrect programming, it can still be reprogrammed until it is correct, so there will be no waste.

　　5. Repeated system testing can be performed

　　The system designed with 89C series single chip microcomputer can be repeatedly tested; different programs can be programmed into each test, which can ensure that the user's system design is optimal. Moreover, it can be modified according to the needs and development of users, so that the system can keep up with the latest requirements of users.

　　Decryption method:

　　For ATMEL 89C series chips, according to the characteristics of their memory, the simple method is to find a way to remove the password, because OTP storage cannot be electrically erased, but can be erased with ultraviolet light. So as long as you can control it to only erase the password part and retain the program segment, then such a chip is not encrypted.

　　If this still doesn't work, then if you de-layer the chip and take a photo of the memory, because the code exists in the form of charged code points, then dye the photo, distinguish 1 and 0, read out and sort, and you will get the code in the memory. There are many methods and means for decryption. The above is just a brief introduction. As a professional decryption technician, when you make a plan after getting the chip, you must first consider the decryption cost and use the lowest cost to achieve the purpose of decryption. Because I have seen many customers who don't understand encryption and decryption and believe in the propaganda of some irregular companies, spend a lot of money not to make the product better, but to consider too many encryption methods, and even don't use a certain chip for fear of being decrypted. In fact, if you know some encryption and decryption technologies, you won't have that idea.