In XT, LP, HS or HSPLL Oscillator modes, a crystal or ceramic resonator is connected to the OSC1 and OSC2 pins to establish oscillation to read Protected MCU PIC16F1826 Firmware.

The oscillator design requires the use of a parallel cut crystal.Different capacitor values may be required to produce acceptable oscillator operation. The user should test the performance of the oscillator over the expected VDD and temperature range for the application of Extracting MCU PIC18F442 Code. See the notes following Table 2-2 for additional information.

Note 1: Higher capacitance increases the stability of the oscillator but also increases the start-up time.

2: When operating below 3V VDD, or when using certain ceramic resonators at any voltage, it may be necessary to use the HS mode or switch to a crystal oscillator.
3: Since each resonator/crystal has its own characteristics, the user should consult the resonator/crystal manufacturer for appropriate values of external components.
4: Rs may be required to avoid overdriving crystals with low drive level specification.
5: Always verify oscillator performance over the VDD and temperature range that is expected for the application.

The EC and ECIO Oscillator modes require an external clock source to be connected to the OSC1 pin. There is no oscillator start-up time required after a Power-on Reset or after an exit from Sleep mode. In the EC Oscillator mode, the oscillator frequency divided by 4 is available on the OSC2 pin. This signal may be used for test purposes or to Unlock microcontroller protected eeprom.