Hi I have had the RTC interrupts running bare metal for years.
The interrupt is goes off every second. The ISR increments a counter.
This counter indicates the routine is being called dozens of times (or it appears so).
This was tolerable but i could never figure out if this was some spurious IRQ activity.
Now that ethernet/DMA is running, and much more MPU activity, the RTC occasionally
causes spurious MPU hang.