how to simulate a clock monitoring failure

Can someone guide me how to simulate a clock monitoring failure?
Now I`ve test it by following 2 steps:

1. set GTMSEL(GTM monitoring frequency) to 7.5MHz:
SCU_CCUCON4.B.GTMSEL = 3u
2. set GTMDIV=20 => fgtmmon/GTMDIV=80MHz/20=4MHz:
SCU_CCUCON4.B.GTMDIV = 20u
I expect the SMU alarm(GTM clock out of range) would be raised as the actual clock is not match the monitor frequency,
but no SMU alarm can be observed

I`m not sure if there is some step missing or wrong. Please guide me.


Thank you in advance