Hi @linxianti,
The CMU is not connected to the FCCU, and only a few VLD sources are linked.
For reference, here is a simple CMU example that uses the RTD MCAL MCU driver:
https://community.nxp.com/t5/S32K-Knowledge-Base/Example-S32K344-MCAL-MCU-ClockMonitor-v1-0-S32DS36-...
To test LVD functionality, you can manipulate the power supply voltage.
By the way, SPD/SAF also use the NCFF injection:

Regards,
Daniel
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