Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Atmel/ATSAM3S1C/PMC/CKGR_PLLBR#0x0
PLLB Register
Divider
PLLB Counter
PLLB Multiplier
https://github.com/cmsis-svd/cmsis-svd-data