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DDR3 burst size


Hello everybody


I have a system with CYCLONE V and DDR3 2Gbit memory (16bit data bus and 14 bit address bus). The DDR3 is connected to HMC pins of the FPGA. When i go to the UniPHY memory DDR3 component, Controller Settings tab, there is a drop down menu labeled Maximum Avalon MM burst length.


I would ask if someone can tell me, is this the burst length of the DDR3 memory chip, or the burst length of the UniPHY component?


I am asking because i can not seem to find any DDR3 memory with burst size bigger then 16, while in the UniPHY settings there is even 128.


How are the burst size of DDR3 memory and UniPHY related?


Thank you

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2 Replies
Honored Contributor III

I believe that's the Avalon burst length, not the external memory burst length.


Thank you for the answer.


Can you or anybody else then further elaborate how are Avalon burst length and DDR3 external memory burst length related.


When i read the datasheet of the DDR3 the BL is 8. Then there is also the issue of address boundary. Since I wrote my own mm master to write/read to and from DDR3 in this case does it mean that i have to only provide an address and burst length to UniPHY and all the correct addressing and data access will be automatically arranged or do i have to make sure that boundary addressing is handled correctly and every 8 access (assuming DDR BL) my mm master must update the address?


Thank you