13.10 Fail-Safe Clock Monitor

The Clock System includes a Fail-safe Clock Monitor (FSCM). The FSCM monitors the SYS_CLK for continuous operation. If it detects that the SYS_CLK failed, it switches the SYS_CLK over to the FRC oscillator and triggers an NMI. The FRC is an untuned 8 MHz oscillator that drives the SYS_CLK during an FSCM event. When the NMI is executed, software can restart the main oscillator or shut down the system.

In the Sleep mode, both the SYS_CLK and the FSCM halt, preventing FSCM detection.