Clone ATMEGA649A Microcontroller Heximal from its eeprom and flash memory, embedded binary file will be recovered from mcu atmega649a, and flash content inside processor atmega649a will be readout in the status of unlocked;
The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system clock cycles from an edge has been applied to the T1/T0 pin to the counter is updated.
Enabling and disabling of the clock input must be done when T1/T0 has been stable for at least one system clock cycle, otherwise it is a risk that a false Timer/Counter clock pulse is generated.
Each half period of the external clock applied must be longer than one system clock cycle to ensure correct sampling when cracking mcu atmega644 memory. The external clock must be guaranteed to have less than half the system clock frequency (fExtClk < fclk_I/O/2) given a 50/50% duty cycle.
Since the edge detector uses sampling, the maximum frequency of an external clock it can detect is half the sampling frequency (Nyquist sampling theorem).
However, due to variation of the system clock frequency and duty cycle caused by Oscillator source to unlock atmega644a mcu program file (crystal, resonator, and capacitors) tolerances, it is rec- ommended that maximum frequency of an external clock source is less than fclk_I/O/2.5