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Honored Contributor
Honored ContributorSteps to constrain a design
Hello, I'm trying to understand timing constraints and I have a really hard time trying to figure out how this works. The first thing is the representation of setup and hold times. In my e...
Altera_ForumHonored Contributor
Honored Contributor --- Quote Start --- I generally find the most difficult part with hold time is that the default hold relationship follows the setup relationship, so if you add a multicycle -setup, the default hold relationship changes. That's usually the biggest stumbling block. --- Quote End --- I think that as direct consequence of internal definitions used by tool i.e. Setup Check (SC) = current latch – previous launch Hold Check1 (HC1) = current launch – previous latch The above definitions assume multicycle of 1 for setup and 0 for hold according to tool's perspective. When user sets multicycle of 2 to setup then that modifies above SC definition of next latch edge by one clock forward as requested. However it does not modify definition of HC1 which will check a launch edge with previous latch edge, this is not right as multicycle requires checking a launch edge with the one before previous latch and so a hold multicycle of 1 is needed to modify the definition backwards by one edge. Purely a tool issue.
