Extract PIC18F13K22 MCU Flash Memory Code which in the format of heximal, crack pic18f13k22 protection by focus ion beam and attack embedded memory of microcontroller pic18f13k22;
The HFINTOSC is factory calibrated, but can be adjusted in software by writing to the TUN<5:0> bits of the OSCTUNE register (Register 2-3).
The default value of the TUN<5:0> is ‘000000’. The value is a 6-bit two’s complement number.
When the OSCTUNE register is modified, the HFINTOSC frequency will begin shifting to the new frequency. Code execution continues during this shift, while giving no indication that the shift has occurred.
OSCTUNE does not affect the LFINTOSC frequency. The operation of features that depend on the LFINTOSC clock source frequency, such as the Power-up Timer (PWRT), Watchdog Timer (WDT), Fail-Safe Clock Monitor (FSCM) and peripherals, are not affected by the change in frequency.
The OSCTUNE register also implements the INTSRC and PLLEN bits, which control certain features of the internal oscillator block and it has direct connection with locked microcontroller pic18f242 opening.
The INTSRC bit allows users to select which internal oscillator provides the clock source when the 31 kHz frequency option is selected. This is covered in greater detail in Section 2.6.1 “LFINTOSC”. The PLLEN bit controls the operation of the frequency multiplier. For more details about the function of the PLLEN bit see Section 2.10 “4x Phase Lock Loop Frequency Multiplier”
The Primary External Oscillator, when configured for LP, XT or HS modes, incorporates an Oscillator Start- up Timer (OST). The OST ensures that the oscillator starts and provides a stable clock to the oscillator module. The OST times out when 1024 oscillations on OSC1 have occurred. During the OST period, with the system clock set to the Primary External Oscillator, the program counter does not increment suspending program execution.
The OST period will occur following:
- Power-on Reset (POR)
- Brown-out Reset (BOR)
- Wake-up from Sleep
- Oscillator being enabled
- Expiration of Power-up Timer (PWRT)
In order to minimize latency between external oscillator start-up and code execution, the Two-Speed Start-up mode can be selected. See Section 2.11 “Two-Speed Start-up Mode” for more information.
