2.1.6. The Clock Sources
The PIC18F452 microcontroller can be operated from an external crystal or a ceramic resonator connected to the OSC1 and OSC2 pins of the microcontroller. In addition, an external resistor and capacitor, external clock source, and in some models, internal oscillators can be used to provide clock pulses to the microcontroller. There are eight clock sources on the PIC18F452 microcontroller, selected by the configuration register CONFIG1H. These are
- Low-power crystal (LP)
- Crystal or ceramic resonator (XT)
- High-speed crystal or ceramic resonator (HS)
- High-speed crystal or ceramic resonator with PLL (HSPLL)
- External resistor/capacitor with FOSC/4 output on OSC2 (RC)
- External resistor/capacitor with I/O on OSC2 (port ...