I am looking into the possibility to detect when the system clock PLL loses lock.
The reference manual states: "The PLL may become unlocked, caused by a break of the crystal or the external clock line. In such a case, an NMI trap is generated if it were enabled."
But where can this be enabled to generate the NMI? I have looked at all the SCU registers but have not been able to find an enable bit. This is also not set by default.
In the default configuration I end up with a Bus Error fault if I stop the external crystal. This is not described in the reference manual.
How can this safety feature be used?
