Reverse Engineering PIC18F4550 microcontroller secured heximal
Reverse Engineering PIC18F4550 microcontroller secured heximal and extract the flash program, eeprom data out from it , the file format will be Binary or heximal, restore the firmware into original Microcontroller which will provide the same functions as original PIC18F4550 MCU;
When using the EUSART, for example, an adjustment may be required when it begins to generate framing errors or receives data with errors while in Asynchronous mode.
Framing errors indicate that the device clock frequency is too high; to adjust for this, decrement the value in OSCTUNE to reduce the clock frequency and faciliate the IC code extraction. On the other hand, errors in data may suggest that the clock speed is too low; to compensate, increment OSCTUNE to increase the clock frequency.
It is also possible to verify device clock speed against a reference clock. Two timers may be used: one timer is clocked by the peripheral clock, while the other is clocked by a fixed reference source, such as the Timer1 oscillator. Both timers are cleared but the timer clocked by the reference generates interrupts. When an interrupt occurs, the internally clocked timer is read and both timers are cleared.
If the internally clocked timer value is greater than expected, then the internal oscillator block is running too fast. To adjust for this, decrement the OSCTUNE register. Finally, a CCP module can use free-running Timer1 (or Timer3), clocked by the internal oscillator block and an external event with a known period of time after copying pic16f688 mcu flash memory content (i.e., AC power frequency).
The time of the first event is captured in the CCPRxH:CCPRxL registers and is recorded for use later. When the second event causes a capture, the time of the first event is subtracted from the time of the second event. Since the period of the external event is known, the time difference between events can be calculated.
If the measured time is much greater than the calculated time, the internal oscillator block is running too fast; to compensate, decrement the OSCTUNE register. If the measured time is much less than the calculated time, the internal oscillator block is running too slow; to compensate, increment the OSCTUNE register.