Cortex-R4 and Cortex-R4F Technical Reference Manual: 7.2. Memory types

7.2. Memory types

The ARM architecture defines a set of memory types with characteristics that are suited to particular devices. There are three mutually exclusive memory type attributes:

Strongly-ordered
Device
Normal.

MPU memory regions can each be assigned a memory type attribute. Table 7.2 shows a summary of the memory types.

Table 7.2. Memory attributes summary

Memory type attribute	Shared or Non-shared	Description
Strongly-ordered	-	All memory accesses to Strongly-ordered memory occur in program order. All Strongly-ordered accesses are assumed to be shared.
Device	Shared	For memory-mapped peripherals that several processors share.
	Non-shared	For memory-mapped peripherals that only a single processor uses.
Normal	Shared	For normal memory that is shared between several processors.
	Non-shared	For normal memory that only a single processor uses.

Note

The processor L1 cache does not cache shared normal regions.

For more information on memory attributes and types, memory barriers, and ordering requirements for memory accesses, see the ARM Architecture Reference Manual.

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