| The devices support high levels of security to protect the user firmware from being reverse-engineered.The security features a 128-bit password (hardcoded for 16 wait-states), which the user programs into theflash. One code security module (CSM) is used to protect the flash/OTP and the L0/L1 SARAM blocks.The security feature prevents unauthorized users from examining the memory contents via the JTAG port,executing code from external memory or trying to boot-load some undesirable software that would exportthe secure memory contents. To enable access to the secure blocks, the user must write the correct 128-bit KEY value that matches the value stored in the password locations within the Flash.In addition to the CSM, the emulation code security logic (ECSL) has been implemented to preventunauthorized users from stepping through secure code. Any code or data access to flash, user OTP, or L0memory while the emulator is connected will trip the ECSL and break the emulation connection. To allowemulation of secure code, while maintaining the CSM protection against secure memory reads, the usermust write the correct value into the lower 64 bits of the KEY register, which matches the value stored inthe lower 64 bits of the password locations within the flash. Note that dummy reads of all 128 bits of thepassword in the flash must still be performed. If the lower 64 bits of the password locations are all ones(unprogrammed), then the KEY value does not need to match.When initially debugging a device with the password locations in flash programmed (that is, secured), theCPU will start running and may execute an instruction that performs an access to a protected ECSL area.If this happens, the ECSL will trip and cause the emulator connection to be cu |
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