Agilex™ 7 Hard Processor System Technical Reference Manual
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Ixiasoft
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Ixiasoft
7.3.5.2. FPGA-to-HPS CCU to Memory (Cache Non-Allocate)
The interface from the FPGA to the HPS CCU is ACE-Lite*. These transactions go through the CCU, but can be cached or not cached, based on AxCACHE parameters. Transactions can be privileged or non-privileged depending on memory allocation.
If your logic issues a Cache Non-Allocate transaction, the CCU maintains coherency but does not allocate in the cache. This is useful when you want to maintain coherency but not thrash the cache.
Reads
- On cache hits, read data is returned by the cache.
- On cache misses, read data is returned from main memory and not allocated (stored) in cache.
ATTRIBUTE | VALUE | NOTE |
---|---|---|
ARDOMAIN[1:0] | ’b01 | Inner Sharable |
ARBAR[1:0] | ‘b00 | Normal access, respecting barriers |
ARSNOOP[3:0] | ‘b0000 | ReadOnce |
ARCACHE[3:0] | ‘b1011 | Write-back No-allocate |
AxUSER[7:0] | ‘b00000100 | 0x04 = CCU |
AxPROT[2:0] | ‘b001 | Data access. Secure access. Privileged access. |
AxLEN[7:0] | — |
The burst length for:
|
AxSIZE[2:0] | — | The number of bytes in a transfer must be equal to the data bus width |
AxBURST[1:0] | ‘b01 or ‘b10 | Must be INCR(‘b01) or WRAP(‘b10) |
AxLOCK[1:0] | ‘b00 | Must be normal access |
AxQOS | — | Do not care |
Writes
- On cache hits, write data is stored in cache.
- On cache misses, write data is stored to main memory.
ATTRIBUTE | VALUE | NOTE |
---|---|---|
AWDOMAIN[1:0] | ’b01 | Inner Sharable |
AWBAR[1:0] | ‘b00 | Normal access, respecting barriers |
AWSNOOP[2:0] | ‘b000 | WriteUnique (could be ‘b001 for WriteLineUnique) |
AWCACHE[3:0] | ‘b0111 | Write-back No-allocate |
AxUSER[7:0] | ‘b00000100 | 0x04 = CCU |
AxPROT[2:0] | ‘b001 | Data access. Secure access. Privileged access. |
AxLEN[7:0] | — |
The burst length for:
|
AxSIZE[2:0] | — | The number of bytes in a transfer must be equal to the data bus width |
AxBURST[1:0] | ‘b01 or ‘b10 | Must be INCR(‘b01) or WRAP(‘b10) |
AxLOCK[1:0] | ‘b00 | Must be normal access |
AxQOS | — | Do not care |