Visible to Intel only — GUID: otj1621345496031
Ixiasoft
Visible to Intel only — GUID: otj1621345496031
Ixiasoft
7.3.5.1. FPGA-to-SDRAM direct (Cache Non-Allocate)
The interface from the FPGA to the SDRAM directly is AXI* 4. These transactions route directly to the EMIF circumventing the CCU and are not cached. You must manage coherency in software because the CCU is not involved with this traffic. Transactions can be Privileged or Non-privileged depending on memory allocation.
Reads
Cache is not looked up. Read data is returned directly from SDRAM.
ATTRIBUTE | VALUE | NOTE |
---|---|---|
ARDOMAIN[1:0] | ’b00 | Non-shareable. (non-coherent, non-snooping) |
ARBAR[1:0] | ‘b00 | Normal access, respecting barriers |
ARSNOOP[3:0] | ‘b0000 | ReadNoSnoop |
ARCACHE[3:0] | ‘b0010 or ‘b0011 | Normal Non-cacheable Non-bufferable (or Normal Non-cacheable Bufferable) |
AxUSER[7:0] | ‘b11100000 | 0xE0 = SDRAM direct |
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: 128-, 256-, or 512-bit. |
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
Cache is not looked up. Write data is stored directly to SDRAM.
ATTRIBUTE | VALUE | NOTE |
---|---|---|
AWDOMAIN[1:0] | ‘b00 | Non-shareable. (non-coherent, non-snooping) |
AWBAR[1:0] | ‘b00 | Normal access, respecting barriers |
AWSNOOP[2:0] | ‘b000 | WriteNoSnoop |
AWCACHE[3:0] | ‘b0010 or ‘b0011 | Normal Non-cacheable Non-bufferable (or Normal Non-cacheable Bufferable) |
AxUSER[7:0] | ‘b11100000 | 0xE0 = SDRAM direct |
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 |