Learning accelerated computing and digital signal processing from the very beginning.
Saturday, October 4, 2008
Timing Summary: Minimum Period
The first item in the list is the Minimum period, one of the domains of timing paths. According to Xilinx toolbox, it is the maximum path from all primary inputs to the sequential elements. One good explanation is given by, again, gszakacs in a Xilinx forum.
Minimum period" after synthesis is an estimate of the clock period for signals inside the design. Thus you can invert this to get a feel for maximum clock frequency. This is not a hard actual number, as you can only see the true numbers after place&route. Also this may not be the actual minimum period for the design if you are limited by input and output timing. It only calculates the worst case path timing from clock edge to clock edge for flip-flops within the design. So if you have a path consisting of external input to flip-flop through look-up table to another flip-flop to an external output, only the path from the first flip-flop through the look-up table to the second flip-flop is measured for "Minimum period".
He also added
The minimum clock period depends on paths that go from the Q output of a flip-flip to the D input of another flip-flop in the design...The worst case path may in fact not be connected at the top level. You would need to look at a static timing report to see what the path is and whether you use it...Also note that the timing reported by synthesis is a best-guess estimate of the achievable timing after place and route. This is usually only useful when designing reusable IP for example or some other subsystem you would like to know the possible best case speed of. The real timing performance of a design is only known after place & route and can be found in the post P&R static timing report. Using the advanced properties for static timing report generation you can get a verbose report that includes uncovered paths in case there are critical paths that have not been constrained.
“...it is impossible to explain honestly the beauties of the laws of nature in a way that people can feel, without their having some deep understanding of mathematics. I am sorry, but this seems to be the case." - R Feynman