相关阅读PrimeTimehttps://blog.csdn.net/weixin_45791458/category_12900271.html?spm1001.2014.3001.5482PrimeTime中存在timing_report_unconstrained_paths变量默认值为false该变量控制是否在使用report_timing命令时进行未约束时序路径的搜索。当设计不存在任何时序约束时使用简单的report_timing命令不会报告任何路径如下所示这与Design Compiler是不同的详情见该文静态时序分析报告命令report_timing详解。pt_shell report_timing **************************************** Report : timing -path_type full -delay_type max -max_paths 1 -sort_by slack Design : test Version: W-2024.09-SP2 Date : Mon Mar 17 15:27:33 2025 **************************************** No constrained paths.如果在使用report_timing命令时添加了拓扑选项比如-from/-rise_from/-fall_from、-through/-rise_through/-fall_through、-to/-rise_to/-fall_to且满足这些拓扑选项的时序路径都是未约束的默认情况下不会报告任何路径如下所示。pt_shell report_timing -from [get_ports A] **************************************** Report : timing -path_type full -delay_type max -max_paths 1 -sort_by slack Design : test Version: W-2024.09-SP2 Date : Mon Mar 17 15:37:20 2025 **************************************** No constrained paths.如果将timing_report_unconstrained_paths变量设置为true则使用拓扑选项的report_timing命令会报告未约束路径优先报告延迟最大的路径如果指定了-delay_type min之类的选项则报告延迟最小路径如下所示。pt_shell set timing_report_unconstrained_paths true true pt_shell report_timing -from [get_ports A] **************************************** Report : timing -path_type full -delay_type max -max_paths 1 -sort_by slack Design : test Version: W-2024.09-SP2 Date : Mon Mar 17 15:44:59 2025 **************************************** Startpoint: A (input port) Endpoint: B_reg (rising edge-triggered flip-flop) Path Group: (none) Path Type: max Point Incr Path --------------------------------------------------------------- input external delay 0.00 0.00 r A (in) 0.00 0.00 r B_reg/D (DFFQXL) 0.00 0.00 r data arrival time 0.00 --------------------------------------------------------------- (Path is unconstrained)值得留意的是时序报告下面的(Path is unconstrained)信息需要将其与No Paths区分开后者指的是没有满足拓扑选项的时序路径或因为失效时序弧导致的时序路径消失如下所示。pt_shell report_timing -from [get_ports A] -to [get_ports B] **************************************** Report : timing -path_type full -delay_type max -max_paths 1 -sort_by slack Design : test Version: W-2024.09-SP2 Date : Mon Mar 17 15:46:55 2025 **************************************** No Paths.将timing_report_unconstrained_paths变量设置为true可能会导致运行时间异常增加并出现 UITE-413警告。Warning: Searching unconstrained paths will take longer run-time than expected (UITE-413)