what is the reason for data mask pin in DDR3

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FixitFast

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Hi all


what is the reason of data mask pin in DDR3. What if I make it disable?


please reply
 

possibly RTFM might lead you to your answer.
Most likely if you disable DM, then the data will not get masked. Yes ?

cheers!
 
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It allows writes at 1B granularity. For example, if you need to write exactly 1B to RAM and you have a 64b bus (8B wide) and burst length is set to 8, then the smallest size of data you can write would be 8*8=64B (or 512b). With the data mask, you can mask off 7B of one access, and then mask off all 8B of the remaining 7 accesses in the fixed-length burst.

For similar reasons, it allows you to write 2B or 4B at a time as well.

Otherwise you would need to do a read-modify-write any time you wanted to write less than 64B to RAM!
 

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