PIC32MX Oscillator - Reference Clock

Reference Clock

refclk.PNG

The Reference Clock can be used to drive the SPI peripheral or to generate a clock on the Reference Clock Output (REFCLKO) pin.

The reference clock can be derived from any of the following clock sources:System Phased-Lock Loop,Primary Oscillator,Fast RC,Low-Power RC,USB Phased-Lock Loop output (96 MHz),Secondary Oscillator,System Clock,Peripheral Bus Clock, and Reference Clock input.

Each reference clock has a high-precision divider based on this formula:

refclk_formula.PNG
  • refOscDiv can be any integer from 1 to 32768,
    • when refOscDiv = 0, the output clock = the input clock.
  • trimValue can be any integer from 1 to 512.
​
// ref clock base = FRCPLIB_OSC_ReferenceOscBaseClockSelect (OSC_ID_0, OSC_REFERENCE_1, OSC_REF_BASECLOCK_FRC);// disable ref clockPLIB_OSC_ReferenceOscDisable(OSC_ID_0, OSC_REFERENCE_1);// enable ref clockPLIB_OSC_ReferenceOscEnable(OSC_ID_0, OSC_REFERENCE_1);// refOscDiv = 32768PLIB_OSC_ReferenceOscDivisorValueSet (OSC_ID_0, OSC_REFERENCE_1, 32768);// trimValue = 256PLIB_OSC_ReferenceOscTrimSet(OSC_ID_0, OSC_REFERENCE_1, 256);// ref clock is driven out REFCLKO pinPLIB_OSC_ReferenceOutputEnable(OSC_ID_0, OSC_REFERENCE_1);