Memories Security Attribution

The IDAU is used to indicate the processor if a particular memory region is Secure (S), Non-Secure Callable (NSC), or Non-Secure (NS). It can also mark a memory region to be exempted from security checking.

Table 1. IDAU Memory Attribution Definition
Attribute	Description
Non-Secure	Memory can be accessed in Secure or Non-Secure state.
Secure	Memory can only be accessed in Secure state. It cannot be called from Non-Secure state.
Non-Secure callable	Memory can only be accessed in Secure state, but can be called from Non-Secure state.
Exempt	No attribution check will be done, and the operation will take place on the bus

Note: Refer to " SAM L11 Security Attribution" chapter for the detailed SAM L11 memories and peripherals security attribution description.

The Cortex-M23 will search each access (fetch or data) in the IDAU, which returns the privilege information about that specific address. If the access is not permitted, the CPU enters a HardFault exception.

The IDAU memory region's attributes are partly hardwired and partly set by NVM configuration fuses, and are loaded into the IDAU by the Boot ROM before application execution. The IDAU memory region's attributes are blocked for further writes from the application, but their current state can still be read through dedicated IDAU registers.

Note: Refer to the "SAM L11 IDAU Memory Mapping Registers".