Visible to Intel only — GUID: suc1415234387672
Ixiasoft
Visible to Intel only — GUID: suc1415234387672
Ixiasoft
10.3.15.1. AxUSER and AxCACHE Attributes
ARUSER[0] and AWUSER[0] Bits
The ACP distinguishes between shared and non-shared requests with the ARUSER[0] and AWUSER[0] signals. The other AxUSER signals, AxUSER[4:1] are not interpreted by the SCU and are simply forwarded to the L2 cache. They are typically set to AxUSER[4:1] = b'1111.The AxCACHE[1] attribute signals must also be set to allow L1 caches to be snooped. Sideband signals ARUSER[4:1] and AWUSER[4:1] convey the inner cache attributes.
The table below shows how the AxUSER[0] bit determines whether a request is shared or non-shared. ARUSER[0] applies to read transactions, and AWUSER[0] applies to write transactions.
ARUSER[0] or AWUSER[0] |
Sideband Signal Information |
---|---|
1 | Shared request |
0 | Non-shared request |
Other AxUSER bits from the ACP are not interpreted by the SCU but are forwarded to the L2 cache.
ARCACHE[4:0] and AWCACHE[4:0] Bits
The Cortex*-A9 MPU only interprets ARCACHE[1] and AWCACHE[1] from ACP requests. All other attributes are forwarded to the L2 cache. AxCACHE[1] is used in combination with AxUSER[0] to detect a coherent access. If AxCACHE[1]=0x1, (normal memory) and AxUSER[0]=0x1, then the access is considered coherent. All ACP requests with AxCACHE[1]=0x0 or AxUSER[0]=0x0 are seen as non-coherent requests.
ARCACHE[1] or AWCACHE[1] |
ARUSER[0] or AWUSER[0] |
Access Type |
---|---|---|
1 | 1 | Coherent request |
0 | 0 | Non-coherent request |