ARM r1p3, R4, R4F

Memory Protection Unit

ID013010 Non-Confidential, Unrestricted Access

Figure7-3 Overlapping subregion of memory

7.1.3 Background regions

Overlapping regions increase the flexibility of how the regions can be mapped onto physical

memory devices in the system. You can also use the overlapping properties to specify a

background region. For example, you might have a number of physical memory areas sparsely

distributed across the 4GB address space. If a programming error occurs, the processor might

issue an address that does not fall into any defined region.

If the address that the processor issues falls outside any of the defined regions, the MPU is

hard-wired to abort the access. That is, all accesses for an address that is not mapped to a region

in the MPU generate a background fault. You can override this behavior by programming region

0 as a 4GB background region. In this way, if the address does not fall into any of the other 11

regions, the attributes and access permissions you specified for region 0 control the access.

In Privileged modes, you can also override this behavior by setting the BR bit, bit [17], of the

System Control Register. This causes Privileged accesses that fall outside any of the defined

regions to use the default memory map.

7.1.4 TCM regions

Any memory address that you configure to be accessed using a TCM interface is given Normal,

Non-shared type attributes, regardless of the attributes of any MPU region that the address also

belongs to. Access permissions for an address in a TCM region are preserved from the MPU

region that the address also belongs to. For more information, see About the TCMs on page 8-13.

Stack

0x4000

0x0000 Guard region

0x0800