23.6 Clocks

The clock for the FREQM bus interface (CLK_APB_FREQM) is enabled and disabled by the Main Clock Controller, the default state of CLK_APB_FREQM can be found in Peripheral Clock Masking.

Two generic clocks are used by the FREQM: Reference Clock (GCLK_FREQM_REF) and Measurement Clock (GCLK_FREQM_MSR).

GCLK_FREQM_REF is required to clock the internal reference timer, which acts as the frequency reference.

GCLK_FREQM_MSR is required to clock a ripple counter for frequency measurement. These clocks must be configured and enabled in the generic clock controller before using the FREQM.

The FREQM has also the capability to use other internal clocks as source for frequency measurement. These clocks are chip specific and must be configured and enabled before using the FREQM.