Extract IC PIC16F689 Code from secured memory after break mcu pic16f689 flash and eeprom memory, then readout the firmware from microcontroller pic16f689;
The HFINTOSC is factory calibrated but can be adjusted in software by writing to the OSCTUNE register (Register 3-2). The default value of the OSCTUNE register is ‘0’. The value is a 5-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. There is no indication that the shift has occurred.
OSCTUNE does 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.
The Low-Frequency Internal Oscillator (LFINTOSC) is an uncalibrated 31 kHz internal clock source. The output of the LFINTOSC connects to a postscaler and multiplexer (see Figure 3-1). Select 31 kHz, via software, using the IRCF<2:0> bits of the OSCCON register.
See Section 3.5.4 “Frequency Select Bits (IRCF)” for more information. The LFINTOSC is also the frequency for the Power-up Timer (PWRT), Watchdog Timer (WDT) and Fail-Safe Clock Monitor (FSCM).
The LFINTOSC is enabled by selecting 31 kHz (IRCF<2:0> bits of the OSCCON register = 000) as the system clock source (SCS bit of the OSCCON register = 1), or when any of the following are enabled if extract mcu embedded firmware:
- Two-Speed Start-up IESO bit of the Configuration Word register = 1 and IRCF<2:0> bits of the OSCCON register = 000
- Power-up Timer (PWRT)
- Watchdog Timer (WDT)
· Fail-Safe Clock Monitor (FSCM)
The LF Internal Oscillator (LTS) bit of the OSCCON register indicates whether the LFINTOSC is stable or not. The output of the 8 MHz HFINTOSC and 31 kHz LFINTOSC connects to a postscaler and multiplexer (see Figure 3-1). The Internal Oscillator Frequency Select bits IRCF<2:0> of the OSCCON register select the frequency output of the internal oscillators. One of eight frequencies can be selected via software.
