PIC32MX Oscillator - Fast RC (FRC) Oscillator

Last modified by Microchip on 2023/11/09 09:00

fast RC diagram

The Fast RC (FRC) oscillator is a fast (8 MHz nominal), user-trimmable, internal RC oscillator. The output can drive the System Phased-Lock Loop (PLL) or be divided by 16 or divided using the programmable FRCDIV bits.

The FRCDIV bits configure a selectable output divider that allows the choice of a lower clock frequency from seven different options, plus the direct 8 MHz output. Available lower frequency options range from 4 MHz (divide-by-2) to 31 kHz (divide-by-256).

The FRC Oscillator Tuning (OSCTUN) register allows the user to fine-tune the FRC oscillator over a range of approximately ±12 percent (typical). Each bit increment or decrement changes the factory-calibrated frequency of the FRC oscillator by a fixed amount.

The following MPLAB® Harmony function examples configure the FRC divider and tune values at run-time.

// Tune = 0 (no deviation from nominal)
PLIB_OSC_FRCTuningSelect(OSC_ID_0, 0);