The simple decryption of the single-chip microcomputer is to erase the encryption lock bit in the chip. Due to the unreasonable timing design of the AT89C series MCU erase operation. It is possible to first erase the encryption lock bit before erasing the on-chip program.
The timing of the AT89C series MCU erase operation is: Erase Start----"Erase Operation Hardware Initialization (10 microseconds)----"Erase Encryption Lock Bit (50----200 microseconds)-- - "Erase the data in the on-chip program memory (10 ms) -----" erase ends. If the program is used to monitor the erase process, the erase operation is terminated once the encryption lock bit is erased, and the on-chip program memory is further erased. The over-extended microcontroller becomes an unencrypted microcontroller. The on-chip program can be read out via the bus.
There are two unbreakable encryption methods for the AT89C series MCU.
First, the encryption method for permanently destroying the encryption bit of the single chip. Referred to as OTP encryption mode.
Second, the encryption method of the data bus of the single chip is permanently destroyed. Referred to as the bus encryption mode. AT89C series MCU OTP encryption mode principle This programming encryption algorithm burns out the encryption lock bit (breaks the silicon chip inside the chip), does not damage other parts, and does not occupy any resources of the MCU. The encryption lock bit is no longer erased after being burned out. The 89C51/52/55 has three encryption bits to further increase the reliability of encryption. Once encrypted in OTP mode, the encryption bits in the MCU and the data in the program memory cannot be erased again. The 89C51/52/55 MCU seems to be a one-time programming OTP MCU.
If the length of the user program is greater than the capacity of the on-chip memory of the 89C51 microcontroller, the OPT mode can also be used for encryption.
The specific method is as follows:
1. Extend a large-capacity program memory as usual, such as 27C512 (64K).
2. Arrange the key program parts in the first 4K of the program.
3. Write the entire program to 27C512 and fill the first 4K of 27C512 with 0.
4. Cure the first 4K of the program to AT89C51 and encrypt it with OPT mode.
5. Connect the EA pin of the MCU to a high level. The first 4K of this program runs inside the microcontroller, and the latter 60K runs off-chip. The pirate can't read the first 4K program of the program, even if he knows that 60K will not help.
AT89C series MCU refines the bus encryption mode principle. Because the program code in the MCU chip is finally read through the data bus, if one of the data buses guiding the MCU is permanently destroyed, the decryptor cannot erase the encryption bit. Read the correct code for the program within the slice. The data bus of 89C1051/2051 burns the P1.0 port of 89C2051 in P1 port bus mode. The original program code is 02H, 01H, 00H. The data read is 03H, 01H, 00H. The lowest bit is always 1, and the program code read is obviously wrong. This encryption mode is used to encrypt the 89C1051/2051 microcontroller. The disadvantage is that it occupies the resources of the microcontroller. The development designer should only reserve the exit line P1.0 when designing the single-chip hardware system, and then use the burn bus mode to encrypt the single-chip microcomputer.
Front Screen Glass Lens For Iphone
Glass Cover For Iphone,Front Screen Outer Glass Lens,Glass Cover With Oca,Glass Cover For Touch Screen
Shenzhen Xiangying touch photoelectric co., ltd. , https://www.starstp.com