AN54439 describes how to configure hardware and firmware for PSoC 3 or PSoC 5LP using the integrated oscillator subsystems and external crystal or ceramic resonators. The PSoC 3 and PSoC 5LP microcontrollers can use a variety of clock sources. Among these, there are two oscillators that can be used with external passive components to generate clock signals with more frequency accuracy than the internal main oscillator (IMO).
