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Data width of DDR SDRAM in Nios II stratix II edition

Honored Contributor II

what is the Data width of DDR SDRAM in Nios II stratix II edition(EP2S60F673C3). 

It has 32 MB DDR SDRAM and is Micron's MT46V16M16
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Honored Contributor II

The physical interface is 16 bits wide so on the Avalon-MM side it'll look like a 32 bit memory (due to the double data rate). Depending on the burst length you set for the DDR SDRAM you'll get the following Avalon-MM burst lengths: 


DDR burst length = 2 --> Avalon-MM burst length of 1 (i.e. non-bursting) 

DDR burst length = 4 --> Avalon-MM burst length of 2 

DDR burst length = 8 --> Avalon-MM burst length of 4 


The reason for the burst length being cut in half is that half of the burst is consumed by the double data rate (a burst of 2 makes up the rising and falling edge of the clock of data transfer). 


If you want to see an example of a design using it go into the EDS folder and under there should be an examples folder with some designs for each embedded development kit (sorry I don't have the tools installed on this machine so I'm going by memory).
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