02-24-2015 12:46 AM
How can that be done? Let’s say that the input net "rx_net" has 6 loads (registers) A, B, C, D, E and F and I need to constrain the skew between A, B, C and D, but not E and F. Is there a way to accomplish this with the MAXSKEW constraint? Using TIG somehow?
02-24-2015 12:57 AM - edited 02-24-2015 01:00 AM
The skew calculation uses a combination of MAX and[Relative] MIN as follows:
SKEWhold = Max(DST clock delay)- Min(SRC clock delay)
SKEWsetup = Min(DST clock delay)- Max(SRC clock delay)
The below link give some useful information (For 11.X tools example) http://www.xilinx.com/support/documentation/sw_manuals/xilinx11/pce_p_exceptions_maxdelayskew.htm
Also refer below link documents
02-24-2015 06:19 AM
I've looked in the Constraints Guide several times and haven't found anything that applies to my situation. Maybe I'm not looking hard enough...
Note that it is the skew between the data paths to the registers that I'm trying to constrain. Well, four out of the six paths. I don't want to constrain two of the paths and that's the problem.
The constraint I have is:
NET "rx_net" MAXSKEW = 0.5 ns;
This constraint applies to all paths leading to A, B, C, D, E and F. How can I "unconstrain" the paths to E and F?