Hi Kris Bird,
Are you sure your chip is mk20dx256vlk10 not mk20dx256zvlk10?
Because from the reference manual, you will get that mk20dx256zvlk10 don't have RCM_SRS0 register, just have MC_SRSL.
mk20dx256vlk10 have the RCM_SRS0 register, so I think maybe your board is using mk20dx256zvlk10 not mk20dx256vlk10 , then if you use RCM_SRS0, the program will enter in the hardfaul isr .
Then when you create the project, you should choose mk20dx256zvlk10 instead of mk20dx256vlk10 .
Wish it helps you!
Have a great day,
Jingjing
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