12.4.4 Internal Fast RC (FRC) Oscillator

The dsPIC33A devices contain one instance of the Internal Fast RC (FRC) Oscillator. The FRC provides a nominal 8 MHz clock without requiring an external crystal or ceramic resonator, which results in system cost savings for applications that do not require a precise clock reference. The application software can tune the frequency of the oscillator using the TUN[5:0] bits in the FRC Oscillator Trim register FRCTUN.

The Internal FRC Oscillator starts quickly. Unlike a crystal oscillator, which can take several milliseconds to begin oscillation, the Internal FRC starts oscillating immediately.