MPUIR_DREGION
#define MPUIR_DREGION_SZMASK (0xFF << MPUIR_DREGION)
dregions = iregions = (mpuir & MPUIR_DREGION_SZMASK) >> MPUIR_DREGION;
max_regions = (mpuir & MPUIR_DREGION_SZMASK) >> MPUIR_DREGION;