RC Oscillator

There's charts in the data sheets, that show R/C and how the frequency will vary with voltage.

and temperature.

- Steve

... and tolerance of the components, and component behavior over changing temps, and ... The general point is that RC oscillation in this context provides and approximate frequency. Applications requiring precise timing ought to use crystals instead. For many things, though, an RC oscillator is fine and it has the benefit of being able to clock the PIC at frequencies well below those possible with a crystal. This is handy if you: a) Don't need an accurate time reference and b) Want to reduce the PIC power consumption. For example, I use an RC oscillator in my keypad decoder