Honored ContributorIn my design, after analysis in TimeQuest, there are 4 paths that hold time are violated, the slack time is negative. What is normal approach to handle the case that hold time is violated?
Thanks very much.
Honored ContributorDo you have the Fitter option to "Optimize Hold Timing" for "All Paths" turned on? If so, then you may need to over-constrain the failing Hold paths with a set_min_delay constraint.
Honored ContributorHonored ContributorYes, I should have mentioned that. That option should always be on. I'm not even sure why it is an option.
Honored ContributorHonored ContributorSorry, just got back from 2 week's vacation today. If you haven't figured this out yet, try this (assuming your Hold Relationship is 0):
set_min_delay 0.200 -from <source node> -to <destination node>. If this isn't enough, you can try increasing the amount from 200 ps to a larger number.Honored Contributorall those fitter options may help you in timing closure if you need to get the design generated asap. but in the long run, if you still encounter the timing violation too often, you need to revisit your design.
firstly, constraint the paths properly. the nets which are supposed to be multicycle (doesn't need to reach the destination by 1 clk cycle) and false paths should be specified, to ease up the fitter process. ultimately, read and apply some design for performance techniques. reduce fanouts by using duplicated registers, apply pipelining. this will get rid of your timing issue once and for all.Honored ContributorHonored Contributorideally you would like to go to chip planner and place the design element by element. altera has good manual on that, named Analyzing and Optimizing the Design Floorplan with the Chip Planner.in it you can actually see where physically your module is located in which elements, connections and delays between each element, so on. never used it. iv heard that somehow timing analyzer gives you a file. you can feed that file back to fitter and fitter will take in consideration all the delays and fit to avoid the delays. never used it aswell :) hope it will guide you to the correct direction.
Honored ContributorThanks very much, ilik. I will try.
