Hi Wu,
just few notes:
1. The initial load from Flash during MCU start doesn't count into the write-once limit.
2. the CPMUCOP_RSBCK bit may be changed anytime when CPMUCOP_WRTMASK=1. In such a case, the write into WCOP and CR[2:0] has no effect.
I hope it helps you.
Have a great day,
Radek