4.17.12 MCK Frequency Monitor

The frequency of MCK can be monitored with the main RC oscillator. This monitoring can only be performed if the MCK frequency is at least three times faster than the embedded main RC oscillator. This function is enabled by writing a ‘1’ to PMC_IER.MCKMON.

An error on the MCK frequency can lead to a PMC interrupt.

When the corresponding PMC interrupt is enabled, the status of the MCK monitoring can be read on PMC_SR.MCKMON. This status is cleared on read.

Once enabled, the monitor continuously counts the number of MCK cycles within 15 cycles of the embedded main RC oscillator. The result is then compared to threshold values defined in the PMC_MCKLIM register. Two levels of threshold can be defined to generate an interrupt.