Monday, June 29, 2009

Multiple MIG 3.0 / 3.1 cores

How do you implement multiple DDR2 MIG cores in a single design? I guess the first question is how do you implement and integrate a single MIG core? I have been using the Core Generator from within ISE to add cores to my design. A MIG core is added by creating the core from within ISE which also automatically adds the generated xco file to the project. What does this mean for a MIG core? Let's assume you've named the core mig_a. A MIG core is open source - it creates all the sources under the folder
When you compile your project with the mig_a.xco file in your project, then it's just like you've added all of the rtl sources manually. This will enable you to instantiate the module mig_a.

Remember that you must take the UCF constraints as created in
and copy them over to your main UCF file.

In order to implement two DDR2 cores you would create mig_a.xco and mig_b.xco. The first issue you run into is with conflicting UCF constraints due to both mig_a and mig_b using identically named constraints. This is easy to solve, and shouldn't cause too much of a headache. If someone knows of a better way to do this I'd love a comment explaining.

The next issue is conflicting source component names. Here's the simple trick to solve those. DON'T USE THE XCO FILES! The DDR2 cores' source files are identical! The only difference in them are the parameters used at the top level instantiation file. Insert the files
ipcore_dir/mig_a/user_design/rtl/*.v and

The final issue is the conflicting IODELAY_GRP name which by default in MIG's cores is set as "IODELAY_MIG." This should be changed in mig_a.v or mig_b.v but preferably in both for clarity's sake so that they don't conflict with each other. Use names like "IODELAY_MIG_A" and "IODELAY_MIG_B."

This solves all the conflicting component issues. You can now freely update your cores from MIG 3.0 to 3.1 without having to manually modify any files. You are using the Xilinx created files just as they are and without any ugly conflicts.


1 comment:

  1. Hi

    I am trying to interface DDR2 with Virtex 5 board, but I am not able to do so.

    Can you please help me out.