Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Atmel/AT91SAM9G20/RTT/MR#0x0
Mode Register
Real-time Timer Prescaler Value
Alarm Interrupt Enable
Real-time Timer Increment Interrupt Enable
Real-time Timer Restart
https://github.com/cmsis-svd/cmsis-svd-data