MIG (Memory Interface Generator)

[darrenger]

Thanks Bob,

Your post suggests that it should be possible to modify a MIG memory controller that works for a 512 MB module so that it will also work for a module of another size, say 2GB.  That's great. 

So far I've modified the generics in my 512 MB project as well as the ucf file in the hopes that changing these two things alone will get me a working 2GB project.  Unfortunately, I still see no initialization signal.  I'm thinking now that I should try slowing down the clock from 400 Mhz?  Any other suggestions would be fantastic.

Thanks,

Darren

[darrenger]

Hi Bob,

Actually, I may have misunderstood the point of your previous post and I think I now see the wisdom of it.  You are saying that I should get MIG to generate a design for the 512 module and compare what it generates to the working reference design I already have.  The differences that exist between them may indicate what I have to change in order for the MIG generated 2GB design to work.  I like the idea.  Have you had luck with this strategy before?

Darren

[eteam00]

Have you had luck with this strategy before?

Yes.  This strategy is called debug one problem at a time or make only one change at a time.  It's not luck, it's good design debugging discipline.

-- Bob ElKind

[darrenger]

Thanks for the advice.  However, there's no guarantee that what differences there are between the ref and mig-generated 512 designs will be the very same that exist between a working Mig generated 2GB design and the raw Mig generated design.  If they are so identical, then i'd say you had some good luck...

[eteam00]

I've offered advice, and you seem to refuse it.  At this point you have no idea whether your problems are related to 2GB (or 4GB) compatibility, with MIG software design, or your understanding of how to make MIG-created design files work for you.

What do you have to lose by eliminating each of these issues one by one, rather than all at once ?

I've been a design engineer for 30+ years, luck had less to do with my success than having enough humility to learn from others.

- Bob Elkind

[darrenger]

Wow, I thanked you for your advice and I haven't refused it.  Nothing I said indicated otherwise.

Rather than continuing a debate about whether luck is ever involved in solving a problem quickly, I'll leave it at that. 

[eteam00]

I apologise for misreading your previous post.  I took your post as a dismissal of the usefulness of the debug 512MB before trying 2GB approach.

I'm looking forward to your progress updates, they should be interesting for a number of visitors to these forums.

- Bob Elkind

[darrenger]

No problem.  Thanks, I'll do my best to keep everyone updated. 

Cheers,

Darren

[darrenger]

OK, here's an update for everybody.

As intended, I managed to initialize a 4GB SODIMM in my ML605 and tested that I can properly and write and read 2GB of it.  I'd qualify this as a success.  For those who are interested in how I did it, here are some simple steps:

1.  In the ML605, get the 512 MB ref design to work.

2.  Generate a 2GB MIG controller.

3.  Rip out the clocking that MIG generates and replace it with the clocking in the reference design.  By that I mean, replace the dual-clock clocking scheme that appears in the MIG-generated design with the uni-clock clocking scheme used in the reference design.  (Be sure to adjust the appropriate clock-related generics).

4.  Replace the ucf file that mig-generates with the ucf file in the 512 MB reference design.  Be sure to add the two address pins that the 2GB design requires.

5.  Follow the MIG user-interface timing diagrams to correctly drive ui signals in the MIG controller.

Whether or not this procedure works for you will probably depend on the specs of the memory module you choose.  I tried to get a 4GB module that matched up as closely as possible with the 512 MB module that I had working.

According to Xilinx, the ML605 does has not support dual-rank SODIMMs, hence my intention to write to only one rank of my 4GB dual-rank module.  If I do succeed in getting the 4GB module to work in its entirety, I'll post again.  However, this is not a priority for me at the moment.

good luck.

Darren