Verilog综合(synthesis)过程中出现 found timing loop.的critical warning

 “found timing loop”概述

        found timing loop出现在critical warning警告中,是不可忽略的警告,如果found timing loop不消除,代码最终将无法执行。found timing loop通常是在模块例化过程中将同一模块的input与output直接相连;或者是由于模块中的组合逻辑形成了latch。

 “found timing loop”警告的位置查找方法

(1)查阅message

 “found timing loop”无法通过message、log等查阅,也不会提示代码位置,但会提示所在模块。以下图举例

 在上图模块中,出现了29个 “found timing loop”警告,且在ZYNQ_Write文件中。

(2)查阅时序检查报告(synthesis->Report Timing Summary)

点击Report Timing Summary

 

 点击OK

Warning (10230): Verilog HDL assignment warning at CNT_CTRL_LED.v(20): truncated value with size 32 to match size of target (25) Warning (10230): Verilog HDL assignment warning at CNT_CTRL_LED.v(36): truncated value with size 32 to match size of target (2) Warning (10230): Verilog HDL assignment warning at CNT_CTRL_LED.v(39): truncated value with size 32 to match size of target (2) Warning (15714): Some pins have incomplete I/O assignments. Refer to the I/O Assignment Warnings report for details Critical Warning (332012): Synopsys Design Constraints File file not found: 'CNT_CTRL_LED.sdc'. A Synopsys Design Constraints File is required by the TimeQuest Timing Analyzer to get proper timing constraints. Without it, the Compiler will not properly optimize the design. Critical Warning (332012): Synopsys Design Constraints File file not found: 'CNT_CTRL_LED.sdc'. A Synopsys Design Constraints File is required by the TimeQuest Timing Analyzer to get proper timing constraints. Without it, the Compiler will not properly optimize the design. Critical Warning (332148): Timing requirements not met Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer. Critical Warning (332148): Timing requirements not met Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer. Critical Warning (332148): Timing requirements not met Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer.
08-30
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