7.7.5. External memory attributes

The Cortex-A57 MPCore multiprocessor uses a combination of inner and outer memory attributes from the MMU to determine how its memory system handles each combination. Table 6.1 shows the Inner and Outer memory attributes used by the L1 and L2 caches to form the internal memory types. Table 7.5 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 MemAttrInner MemAttrExternal memory typeARCACHEAWCACHETREQFLIT[MemAttr]
DevicenGnRnEStrongly-ordered0b00000b00000b0010
DevicenGnREDevice0b00010b00010b0011
DevicenGREDevice0b00010b00010b0011
DeviceGREDevice0b00010b00010b0011
Non-cacheableNon-cacheableNon-cacheable Bufferable0b00110b00110b0001
Non-cacheableWrite-ThroughNon-cacheable Bufferable0b00110b00110b0001
Non-cacheableWrite-BackNon-cacheable Bufferable0b00110b00110b0001
Write-ThroughNon-cacheableNon-cacheable Bufferable0b00110b00110b0001
Write-ThroughWrite-ThroughNon-cacheable Bufferable0b00110b00110b0001
Write-ThroughWrite-BackNon-cacheable Bufferable0b00110b00110b0001
Write-BackNon-cacheableNon-cacheable Bufferable0b00110b00110b0001
Write-BackWrite-ThroughNon-cacheable Bufferable0b00110b00110b0001
Write-Back No-AllocateWrite-BackWrite-Back No-Allocate0b10110b01110b0101
Write-Back Read-AllocateWrite-BackWrite-Back Read-Allocate0b11110b01110b1101
Write-Back Write-AllocateWrite-BackWrite-Back Write-Allocate0b10110b11110b1101
Write-Back Read-Write-AllocateWrite-BackWrite-Back Read-Write-Allocate0b11110b11110b1101

In addition to ARCACHE, AWCACHE, and TXREQFLIT[MemAttr] the multiprocessor 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. See CHI interface signals and ACE interface signals for more information.

Copyright © 2013, 2014 ARM. All rights reserved.ARM DDI 0488D
Non-ConfidentialID012914