7.7.5 External memory attributes

The Cortex-A72 processor uses a combination of inner and outer memory attributes from the MMU to determine how its memory system handles each combination. Table 6-1 Memory attribute combinations shows the Inner and Outer memory attributes used by the L1 and L2 caches to form the internal memory types. Table 7-5 External memory attributes shows how these attributes are used to form the external memory type presented on ARCACHE, AWCACHE, or TXREQFLIT[MemAttr].

Table 7-5 External memory attributes

Outer MemAttr Inner MemAttr External memory type ARCACHE AWCACHE TREQFLIT[MemAttr]
Device nGnRnE Strongly-ordered 0b0000 0b0000 0b0010
Device nGnRE Device 0b0001 0b0001 0b0011
Device nGRE Device 0b0001 0b0001 0b0011
Device GRE Device 0b0001 0b0001 0b0011
Non-cacheable Non-cacheable Non-cacheable Bufferable 0b0011 0b0011 0b0001
Non-cacheable Write-Through Non-cacheable Bufferable 0b0011 0b0011 0b0001
Non-cacheable Write-Back Non-cacheable Bufferable 0b0011 0b0011 0b0001
Write-Through Non-cacheable Non-cacheable Bufferable 0b0011 0b0011 0b0001
Write-Through Write-Through Non-cacheable Bufferable 0b0011 0b0011 0b0001
Write-Through Write-Back Non-cacheable Bufferable 0b0011 0b0011 0b0001
Write-Back Non-cacheable Non-cacheable Bufferable 0b0011 0b0011 0b0001
Write-Back Write-Through Non-cacheable Bufferable 0b0011 0b0011 0b0001
Write-Back No-Allocate Write-Back Write-Back No-Allocate 0b1011 0b0111 0b0101
Write-Back Read-Allocate Write-Back Write-Back Read-Allocate 0b1111 0b0111 0b1101
Write-Back Write-Allocate Write-Back Write-Back Write-Allocate 0b1011 0b1111 0b1101
Write-Back Read-Write-Allocate Write-Back Write-Back Read-Write-Allocate 0b1111 0b1111 0b1101
In addition to ARCACHE, AWCACHE, and TXREQFLIT[MemAttr] the processor also presents the raw outer memory attributes, inner memory type, and Inner and Outer Shareable on dedicated external interface signals RDMEMATTR, WRMEMATTR, and REQMEMATTR corresponding to transactions on ACE read channel, ACE write channel and CHI TXREQ channel, respectively.
Related information
A.9 CHI interface signals
A.10 ACE interface signals
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