29.6.1 Principle of Operation
FREQM counts the number of periods of the measured clock (GCLK_FREQM_MSR) with respect to the reference clock (GCLK_FREQM_REF). The measurement is done for a period of REFNUM/fCLK_REF and stored in the Value register (VALUE.VALUE). REFNUM is the number of Reference clock cycles selected in the Configuration A register (CFGA.REFNUM).
The frequency of the measured clock, , is calculated by
. The error can be maximum two measured clock cycles.