Preserve_Hierarchical_Boundary Assignment

Could you expand on a few questions:

1) What type of components are being merged? Registers, or combinatorial logic?

2) How do you know they're being merged? (Just because it exists in the RTL view but not in th etechnology view doesn't mean it was merged. It may have been synthesized away or something.

3) Most importantly, why don't you want them to be merged? In general, the only time something gets merged is because it is redundant and there's no reason to have it around.

That being said, I'm currently adding redundant registers to a Hardcopy II design so that it can meet timing, and I then add that register to the Assignment Editor and apply the Remove Duplicate Registers = Off and that works(they get merged if I don't do that.). There is also one for Remove Duplicate Logic. If you really want to prevent this, you can put one or both of the hierarchies into a Design Partition, and they won't get merged.

(I just noticed a Preserve Register assignment, which I've never used before but looks like it would do the same thing, and not require a double-negative to get the assignment to do what you want.)