Visible to Intel only — GUID: ppv1676413867760
Ixiasoft
Visible to Intel only — GUID: ppv1676413867760
Ixiasoft
11.8.3.1. FPGA-to-SDRAM Direct (Cache Non-Allocate)
The interface from the FPGA to the SDRAM directly is AXI4. 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.
For reads, cache is not looked up. Read data is returned directly from SDRAM. The following table shows the read data attribute list.
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: 64-,128-, or 256-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 |
For writes, cache is not looked up. Write data is stored directly to SDRAM. The following table shows the write data attribute list.
Attribute | Value | Note |
---|---|---|
AWDOMAIN[1:0] | ‘b00 | Non-shareable (non-coherent, non-snooping) |
AWBAR[1:0] | ‘b00 | Normal access, respecting barriers |
AWSNOOP[3:0] | ‘b0000 | 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 |