[Question]: DDR Burst Read

[sajjadahmed677]

Hi everyone! I am trying to simulate my design with DDR-C and found that it only supports fixed burst size (ar_size and aw_size) of value 6. which means it always do burst size of 512 bits. So, my question is do other DDR controllers (A, B and D) also have same configuration or do they support variable burst size?

Another thing is how can i use this fixed configuration DDR with my 64bit design where i need multi beat bursts of 64 bit?

[jacobmgn]

Hello,

Thanks for reaching out. We're looking into this and hope to have an answer for you soon.

[sajjadahmed677]

Thanks @jacobmgn! Looking forward to your response.

[jacobmgn]

I am trying to simulate my design with DDR-C and found that it only supports fixed burst size (ar_size and aw_size) of value 6. which means it always do burst size of 512 bits So, my question is do other DDR controllers (A, B and D) also have same configuration or do they support variable burst size?

The simulation BFM ( https://github.com/aws/aws-fpga/blob/master/hdk/common/verif/models/sh_bfm/sh_bfm.sv#L1510 ) has a fixed size of 6 for simplicity. This constraint may not match the actual shell implementation. You can explore different sizes by modifying the test bench/

• All of the DDR controllers should support variable burst size

You should be able to modify sh_bfm to take the actual ar_size and aw_size, but you will need to ensure compliance to the AXI specification.

As a side note, PCIM has a limitation, though this doesn't apply for sh_DDR.

Another thing is how can i use this fixed configuration DDR with my 64bit design where i need multi beat bursts of 64 bit?

• It is possible to implement narrow transfers by following the AXI protocol. There is another option, which is to use Xilin'x AXI data width converter
  • https://docs.xilinx.com/v/u/en-US/pg059-axi-interconnect

[kyyalama2]

assuming resolved. Please feel free to re-open if you need further help

Thanks