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

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MaJa_1553636
Level 3
Level 3
First like given

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

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2 Replies
odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted

I suggest to add ClockSync component to 100Hz clock to sync the clocks from different domains.

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MaJa_1553636
Level 3
Level 3
First like given

Ah, I missed that one. Will try thanx.

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