2 Replies Latest reply on Feb 6, 2016 11:22 PM by obiwanjacobi_1553636

    Help with Warning: "Asynchronous path(s) exist" (clocks)

    obiwanjacobi_1553636

      Hi,

         

      I start having these warnings when I compile my project. I think I understand what they mean (that the delay in the data may be too large and the clock will arrive too early and clock in garbage) but I don't understand how they relate to my design. It is not obvious to me where to look and what to fix.

         

      Project name is SystemController and I have two clock components (CPU_CLK and CPUCLK_FAST) that I use to clock an external Z80 uP. The fast clock is in Mhz, the slow clock is 100Hz.

         
          

      Static timing analysis ...

          

      Warning: sta.M0021: SystemController_timing.html: Warning-1350: Asynchronous path(s) exist from "CyBUS_CLK" to "CPUCLK_FAST(routed)". See the timing report for details.

          

      Warning: sta.M0021: SystemController_timing.html: Warning-1350: Asynchronous path(s) exist from "CyBUS_CLK" to "CPU_CLK(routed)". See the timing report for details.

          

      Warning: sta.M0021: SystemController_timing.html: Warning-1350: Asynchronous path(s) exist from "CPUCLK_FAST(routed)" to "CPU_CLK(routed)". See the timing report for details. 

          

      Warning: sta.M0021: SystemController_timing.html: Warning-1350: Asynchronous path(s) exist from "CPU_CLK(routed)" to "CPUCLK_FAST(routed)". See the timing report for details.

         
         

       

         

      Although these do not seem to be critical at the moment, I would like to fix them.

         

      Any hints or suggestions would be most welcome.

         

      Marc