同步电路不稳定状态？

你能分享一些关于这个话题的知识吗？
关于亚稳态的主题，互联网上有大量的信息。
这些信息不需要再次重复，因为它很容易获得。
建议您使用搜索引擎查找有关此主题的一些阅读材料。
第二个问题如下图所示：在电压介于0和1之间时，第一个FF捕获数据时的状态是什么（例如，在LVCMOS33中，它可能是1.5V）。
在有效时钟沿之后立即的状态将是0,1或这两种状态之间的某个电压电平。
它主要取决于电路增益，时序和输入信号电压电平与寄存器逻辑阈值电压的比较。
什么是第二个FF的状态，1个时钟之后？
主要取决于电路增益和时钟频率，第二个FF（稍后一个时钟周期）的输出也将是0,1或这两个状态之间的某个电压电平。
如果您想更深入地了解亚稳态发生和避免/减少，建议您搜索网络并进行阅读！
- 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

Could you share some knowledge about this topic?
 
There is an abundance of information available on the internet, on the subject of metastable states.  This information does not need to be repeated again, as it is readily available.  Suggest you use a search engine to locate some reading material on this subject.
 
And second question to the picture below: what is the state of first FF when it catches data in the moment when voltage is between 0 and 1 (e.g.  in LVCMOS33 it could be 1.5V).
 
The state immmediately following the active clock edge will be either 0, 1, or some voltage level in between these two states.  It depends on circuit gain, timing, and the input signal voltage level compared to the register's logic threshold voltage, mostly.
 
And what is the state of second FF, 1 clock later?
 
Depending on circuit gain and clock frequency, primarily, the output of the second FF (one clock cycle later) will also be either 0, 1, or some voltage level in between these two states.
 
If you want a deeper understanding of metastability occurence and avoidance/reduction, suggest you search the web and do your reading!
 
-- 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

Summary:
1. Read the manual or user guide.  Have you read the manual? Can you find the manual?
2. Search the forums (and search the web) for similar topics.
3. Do not post the same question on multiple forums.
4. Do not post a new topic or question on someone else's thread, start a new thread!
5. Students: Copying code is not the same as learning to design.
6 "It does not work" is not a question which can be answered. Provide useful details (with webpage, datasheet links, please).
7. You are not charged extra fees for comments in your code.
8. I am not paid for forum posts.  If I write a good post, then I have been good for nothing.

好的，thx。
我在这里找到了一些很好的信息 - > http://www.smdp.iitkgp.ernet.in/PDFXilinxPDFFPGA_Design_Flow16_fpgaDsgnTech_8.pdf



以下为原文

Ok, thx.
 
Some good info i found here --> http://www.smdp.iitkgp.ernet.in/PDFXilinxPDFFPGA_Design_Flow16_fpgaDsgnTech_8.pdf

我建议：http：//www.nxp.com/documents/application_note/AN219.pdf这是1989年 - 这不是一个新问题！
------------------------------------------“如果它不起作用
模拟，它不会在板上工作。“



以下为原文

I suggest:
http://www.nxp.com/documents/application_note/AN219.pdf

It is from 1989 - this is not a new problem!

------------------------------------------
"If it don't work in simulation, it won't work on the board."

在新用户的论坛中有一个关于Metastability的粘性线程会很好。
关于它有很多常见的误解，其中最重要的是，你在实验室中看到的任何问题都是由亚稳态引起的（现代部件中的实际亚稳率是如此之低，以至于你不太可能出现这种情况）
重看）。
另一个误解是亚稳态导致Q输出振荡。
事实上，它通常会显示为在阈值区域中延迟一段时间之前的输出，然后再解析为1或0，例如翻转硬币并让硬币在一个边缘上晃动一秒钟然后掉到头部或尾部。
-  Gabor



以下为原文

It would be nice to have a sticky thread about Metastability in the new user's forum.  There are a lot of common misconceptions about it, not the least of which is that whatever problem you happen to be seeing in the lab is caused by metastability (actual metastable rates in modern parts is so low it's extremely unlikely to show up while you're watching).  Another misconception is that metastability results in oscillation on the Q output.  In fact it normally shows up as an output lingering in the threshold region for some time before resolving to 1 or 0, something like flipping a coin and having the coin teeter on one edge for a second before dropping to heads or tails.
-- Gabor

好的建议，Gabor。
作为NEW USERS论坛中README线程的表面所有者，我很乐意为亚稳态添加一个部分。
已经存在与异步输入相关的几行和链接（参见第2篇“设计基础”部分）。
Gabor（和其他人）：你介意提供这个部分/主题的链接和文字吗？
- 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

Good suggestion, Gabor.
 
As the ostensible owner of the README thread in the NEW USERS forum, I'll gladly add a section for metastability.  There is already a few lines and links relating to async inputs (see post #2, "Design Fundamentals" section).
 
Gabor (and others):  would you mind providing the links and text for this section/subject?
 
-- 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

Summary:
1. Read the manual or user guide.  Have you read the manual? Can you find the manual?
2. Search the forums (and search the web) for similar topics.
3. Do not post the same question on multiple forums.
4. Do not post a new topic or question on someone else's thread, start a new thread!
5. Students: Copying code is not the same as learning to design.
6 "It does not work" is not a question which can be answered. Provide useful details (with webpage, datasheet links, please).
7. You are not charged extra fees for comments in your code.
8. I am not paid for forum posts.  If I write a good post, then I have been good for nothing.