Analog Devices ADuC841 uses serial download mode. ADuC841 decryption unlocks it to recover firmware.

ADuC841 Protection:
- Serial download mode requires a key.
- Flash can be read-protected.
- User code cannot be read directly.
- Security bits lock after programming.

ADuC841 Decryption Methods:
1. Voltage Glitching: glitch VDD during key check.
2. Clock Glitching: fault UART bootloader.
3. Decapsulation: read silicon die directly.
4. Side-Channel: power analysis during key entry.

ADuC841 is used in precision measurement, industrial sensing, and data acquisition.