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Altera_Forum
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19 years ago

32bit SDRAM without byte access?

I have a current design with SDRAM ( MT48LC4M32B; 1Mx32x4) but designed for a DSP (ADS 21161).

Is was planed from the very beginning also to test with a NIOS by omitting the DSP.

My problem is that the DSP is a pure 32 bit processor (no 8 bit access to the RAM …) and

so the layout has all the “DQM[3..0]” connected together. ( http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/sad.gif … yes, I know it’s not okay … http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/smile.gif )

These 4 lines are a kind of byte-select, especially for write accesses.

My question is, has anybody an idea to run this design with a NIOS2 (Cyclone 1C20)

without the ability to write (read) to a specific byte?

From my point of view the heaviest problem is to convince the compiler only to address

the variables LWORD aligned. By the way, a NIOS2 with this SDRAM in a 8 bit mode is up and running, but not very efficient…

Thanks for any suggestions.

Frank
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