Honored ContributorDoes anyone know how to instantiate a register in LUTs? Page 2-17 of the Stratix III handbook indicates that you can get a third register in a single ALM by taking advantage of the feedback between the LUTs. Is there a particular atom you can use or a synthesis option in either Synplify or Quartus? Thanks!
Honored ContributorI don't think there is an attribute or primitive, the fitter just does this for you. I think it's not really a "synthesis" issue. The fitter packs some registers into ALUTs(I've seen this done on a few designs) and therefore has flexibility to move things in and out for better timing and fit. Note that there is no good reason to use these until you're running out of regular FFs.
Honored ContributorWhat does the Resource Property Editor view of this configuration look like? I do not see the dedicated feedback paths that would allow for the third register, only the internal path from the top block to the bottom block. Thanks!
