15.5.7 SAM L11 Secure and Non-Secure Read/Write Accesses

Non-Secure write to EVCTRL, INTENCLR, INTENSET, INTFLAGAHB, INTFLAGx, and NONSECx registers is prohibited.

Non-Secure read to EVCTRL, INTENCLR, INTENSET, INTFLAGAHB, and INTFLAGx registers will return zero with no error resulting.

Non-secure write to a bit of STATUSx registers (by writing to the WRCTRL register) is prohibited if the corresponding bit in NONSECx is zero.

STATUSx bits relating to secure peripherals (i.e., the corresponding bits in NONSECx are zero), read as zero in Non-Secure mode, with no error resulting.