Why is there a need sometimes for an external crystal, even though the MCU have an internal oscillator?
To give you an example, the Atmega328P used in Arduino Uno has an internal 8Mhz internal oscillator, but also has settings for higher clocks. And additionally can be configured to use external oscillators as well. Why?
Similarly, there was a personal project where a PIC32, having 50Mhz CPU, was used with an external 8Mhz crystal for an audio codec.
Many of my assumptions maybe wrong, that is because of an unclear understanding of the need for something external, if there is a default choice.
Some assumptions
- Stability
- Accuracy
- Cost
Please elaborate the exact purpose.
