4.3. Overlapping regions

You can program the protection unit with two or more overlapping regions. When overlapping regions are programmed, a fixed priority scheme is applied to determine the overlapping region attribute that is applied to the memory access (attributes for region 7 take highest priority, those for region 0 take lowest priority).

For example:

Region 2

Is programmed to be 4KB in size, starting from address 0x3000 with Dap[3:0] = 0010. (Privileged mode full access, User mode read only.)

Region 1

Is programmed to be 16KB in size, starting from address 0x0000 with Dap[3:0] = 0001. (Privileged mode access only.)

When the processor performs a data load from address 0x3010 while in User mode, the address falls into both region 1 and region 2, as shown by the shaded area in Figure 4.2. Because there is a clash, the attributes associated with region 2 are applied. Because you are only allowed to perform reads from this region, a Data Abort occurs.

Figure 4.2. Overlapping memory regions

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