Read Microchip PIC18F26K22 MCU Secured Flash Code after attack microcontroller pic18f26k22 fuse bit and crack down pic18f26k22 tamper resistance system;
The HFINTOSC/MFINTOSC oscillator circuits are 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/MFINTOSC frequency will begin shifting to the new frequency. Code execution continues during this shift in the process of duplicate microcontroller pic18f26k20 source code from flash memory. There is no indication that the shift has occurred. The TUN<5:0> bits in OSCTUNE do not affect the LFINTOSC frequency.
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 to extract microchip pic18f23k20 locked memory heximal.
The OSCTUNE register also implements the INTSRC and PLLEN bits, which control certain features of the internal oscillator block. The INTSRC bit allows users to select which internal oscillator provides the clock source when the 31.25 kHz frequency option is selected.
This is covered in greater detail in Section 2.2.3 “Low Frequency Selection”. The PLLEN bit controls the operation of the frequency multiplier, PLL, in internal oscillator modes. For more details about the function of the PLLEN bit, see Section 2.6.2 “PLL in HFINTOSC Modes”.
