如何满足时序约束？

rachid12，
时序收敛的主题是一个复杂的主题..但这里的想法很少......
修复此问题的方法取决于约束失败的类型（周期，OFFSET IN BEFORE，OFFSET OUT AFTER等）以及twr文件中概述的结果逻辑/路由延迟。
例如，如果您使用实际12ns的逻辑延迟和5ns路由延迟来破坏10ns周期约束，则该方法将不同（例如重新流水线或合成设置），而不是在失败时您获得高百分比的路由延迟
路径。
假设你有一个失败的时期约束（通常是最可能的焦虑源）......
如果您的逻辑延迟大于（或更大比例）您的期间，则没有任何数量的地图和标准选项可以帮助您。
合成中的重新流水线可以是一个选项，或者在合成中过度约束设计频率，但我通常更喜欢通过关键路径手动添加额外的寄存器级（注意通过可能并行的相关逻辑来平衡任何延迟）。
如果路由延迟是失败路径的主导，则可以有多种方法，包括放置（删除不良放置LOC或区域约束，添加良好放置）约束，不同的综合或实现选项等。
Xplorer通常是一种很好的尝试方法（非常适合隔夜或周末运行）来验证您的地图/标准选项是否设置为最佳（这取决于设计）。
我已经看到Xplorer很快修复了一些时序收敛问题。
Xplorer是一个独立的perl脚本，最初可单独用于ISE 7.1。
然后将其包含在ISE 8.1中，随后集成到8.2i中的Project Navigator GUI中。
从8.2i开始，您可以通过右键单击Implement Design  - > Properties在ProjNav中访问它。
这里有一个Xplorer属性类别，可以启用它。
当然，您也可以从命令行运行它。注意它不再是真正的perl脚本，而是现在的带有perl包装器的TCL脚本。
我认为这个改变是在8.2i中做出的，但不会发誓。有关Xplorer的更多信息可以在这里找到：http：//www.xilinx.com/ise/implementation/Xplorer.htmhttp：//www.xilinx。
com / xlnx / xil_ans_display.jsp？iLanguageID = 1＆amp; iCountryID = 1＆amp; getPagePath = 21133（7.1i PAR  - 什么是Xplorer脚本？）http://www.xilinx.com/bvdocs/whitepapers/wp229.pdfhttp：/
/www.xilinx.com/publications/xcellonline/xcell_55/xc_xplorer55.htm
请注意，如果你没有运行合成或做任何事情要求重新运行，ProjNav可能会重新运行合成然后翻译（ngdbuild）然后在运行map / par之前，给你一个对话框，说明“这可能会带来什么”
一段时间......你真的想这样做吗？“
因为它将运行map / par的多次迭代。
我只是想确保你知道这一点，然后让它运行，然后回来并发现它在这个对话框中等待。
PlanAhead还有很多很好的功能，这可以在这里提供帮助，但这是一个可选的（阅读额外的$）工具...这里有一些关于你的选择的很好的概述：http：//www.xilinx.com/ise/ise/poster
/0531540_MPM_617_ISE_DP_poster_Final.pdf
祝你好运...
干杯，
BT
== minor editMessage由timpe编辑于09-26-2007 12:10 PM



以下为原文

rachid12, The topic of timing closure is a complex subject.. But here are a few thoughts...
The approach to fix this depends on the type of constraint failing (period, OFFSET IN BEFORE, OFFSET OUT AFTER, etc.) as well as the resulting logic/routing delays outlined in the twr file. For example, if you're failing a 10ns period constraint with an actual 12ns of logic delay and 5ns routing delay, the approach will be different (e.g. repipelining or synthesis settings) than if you've got a high percentage of routing delays on the failing paths. Assuming you've got a failing period constraint (usually the most likely source of angst)...If your logic delay is greater than (or a larger percentage of) your period, no amount of map and par options will help you. Repipelining in synthesis can be an option here or overconstraining the design frequency in synthesis, but I generally prefer to add additional register stages manually through the critical path (taking care to balance any delays through associated logic that may go in parallel). If routing delays are the dominating the failing paths, there can be a variety of approaches including placement (removing bad placement LOCs or area constraints, adding good placement) constraints, different synthesis or implementation options, etc.
Xplorer is often a good approach to try (well-suited for an overnight or weekend run) to verify your map/par options are set optimally (which is design dependent). I've seen a number of timing closure issues quickly fixed by Xplorer. Xplorer was a stand-alone perl script originally available separately for ISE 7.1. It was then included in ISE 8.1 and subsequently integrated into the Project Navigator GUI in 8.2i. Since 8.2i, you can access it in ProjNav by right clicking on Implement Design -> Properties. There is an Xplorer Properties category here which can be enabled.
Of course, you can also run it from the command line as well.
Note that it is no longer really a perl script but now a TCL script with a perl wrapper. I think this change was made in 8.2i, but wouldn't swear to it.
More information on Xplorer is available here:
http://www.xilinx.com/ise/implementation/Xplorer.htm
http://www.xilinx.com/xlnx/xil_ans_display.jsp?iLanguageID=1&iCountryID=1&getPagePath=21133 (7.1i PAR - What is the Xplorer script?)
http://www.xilinx.com/bvdocs/whitepapers/wp229.pdf
http://www.xilinx.com/publications/xcellonline/xcell_55/xc_xplorer55.htmNote that if you haven't run synthesis or did anything to require this to be rerun, ProjNav will likely rerun synthesis then translate (ngdbuild) and then before running map/par, give you a dialog box that says something to the effect of "this could take awhile... do you really want to do this?" as it will run multiple iterations of map/par. I just wanted to make sure you knew this before you let it run for while and came back in and found it waiting at this dialog box. PlanAhead also has a lot of nice features that can be helpful here, but that is an optional (read additional $) tool...
 
Here's a nice overview on some of your options:
http://www.xilinx.com/ise/ise_poster/0531540_MPM_617_ISE_DP_poster_Final.pdf Good luck... Cheers,bt == minor edit


Message Edited by timpe on 09-26-2007 12:10 PM

获得一些想法的另一个好工具是时序分析器工具中的时序改进向导。
如果您是命令行用户，则命令为“timingan”以启动时序分析器。
当您打开.twx文件时，您应该会在失败路径报告中看到指向时序改进向导的链接。
如果您使用ProjNav，请单击Analyze Post Place和Route Timing流程。
这将打开Timing Analyzer。
当您单击“时序改进向导”时，它将分析您的失败路径，并为您提供有关如何满足时序的一些想法。
凯特



以下为原文

Another nice tool to get some ideas is the Timing Improvement Wizard in the Timing Analyzer tool. If you are a command line user, the command is 'timingan' to start the Timing Analyzer.  When you open your .twx file, you should see a link to the Timing Improvement Wizard in your failing path report. If you use ProjNav, click on the Analyze Post Place and Route Timing process. This will open Timing Analyzer. When you click on the Timing Improvement Wizard, it will analyze your failing path and give you some ideas on how to meet timing.   Kate