Mux与Spartan 3A器件中的三态缓冲器哪个更好？

Spartan-3A器件中不存在三态缓冲器。
见XAPP466
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以下为原文

Tri-state buffers don't exist in the Spartan-3A devices.  See XAPP466
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如果我将它编码为三态缓冲区，那么合成会对它做什么？
它仍然作为多路复用器实现吗？
当我查看RTL原理图时，它不允许我深入了解发生了什么。
谢谢。



以下为原文

What does the synthesize do with it if I code it as a tristate buffer?  Does it still implement it as a mux?  When I view the RTL schematic it doesn't allow me to go deep enough to see what's going on.
 
Thanks.

当它到达MAP阶段时，BUFT应该转换为AND-OR结构。
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以下为原文

When it gets to the MAP stage a BUFT should be converted to an AND-OR structure.
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如果您使用ISE / XST进行合成和映射，我认为您提出了错误的问题。
如果您对能够产生最有效的内部MUX实现的编码风格感兴趣，那么有一个Xilinx文档可以专门解决这些问题。
查看Xilinx XST用户指南（UG627），从第68页开始。本文档中有很多好东西。
如前所述，Spartan 3（及更高版本）系列不支持内部三态缓冲区。
内部MUX的两种流行编码样式是CASE语句和IF-THEN-ELSE树。
UG627涵盖了两者（及其差异）。
- 鲍勃埃尔金德
签名：新手的自述文件在这里：http：//forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369总结：1。
阅读手册或用户指南。
你读过手册了吗？
你能找到手册吗？2。
搜索论坛（并搜索网页）以寻找类似的主题。
不要在多个论坛上发布相同的问题。
不要在别人的主题上发布新主题或问题，开始新的主题！5。
学生：复制代码与学习设计不同.6“它不起作用”不是一个可以回答的问题。
提供有用的详细信息（请与网页，数据表链接）.7。
您的代码中的评论不需要支付额外费用。
我没有支付论坛帖子的费用。
如果我写一篇好文章，那么我一无所获。



以下为原文

If you are using ISE/XST for synthesis and mapping, I think you are asking the wrong question.
 
If you are interested in the coding style which will yield the most efficient internal MUX implementation, there is a Xilinx doc which specifically addresses such questions.
 
Check out the Xilinx XST User Guide (UG627), starting at page 68.  Lots of good stuff in this doc.
 
As already mentioned, internal tri-state buffers are not supported in Spartan 3 (and later) families.  The two popular coding styles for internal MUXes are CASE statements and IF-THEN-ELSE trees.  Both (and their differences) are covered in UG627.
 
- Bob Elkind
SIGNATURE:
README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369

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