4.17.14 MCK0 Frequency Monitor

The frequency of MCK0 can be monitored with the main RC oscillator. This monitoring can only be performed if the MCK0 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 MCK0 frequency can lead to a PMC interrupt or a reset of the system (refer to the section “Reset Controller (RSTC)”).

When the corresponding PMC interrupt is enabled, the status of the MCK0 monitoring can be read on PMC_SR.MCKMON. This status is cleared on read.

Once enabled, the monitor continuously counts the number of MCK0 cycles within 15 cycles of the embedded main RC oscillator. The result is then compared to threshold values defined in the PMC_MCKLIM register. Four levels of thresholds can be defined: a first couple of values defines thresholds to generate an interrupt and a second couple of values defines thresholds to generate a reset of the system.