dft测试和功能测试

zhangjirong

请问dft测试和功能测试有什么区别，是不是dft测试可以测试到功能测试不能测到的故障。

waltjung

I will answer your problem briefly.

First of all. DFT is "Design for Testing" It is a method that makes the original design testable.  I thought the question you have is the different between "ATPG and FUNCTIONAL Test"..

The  two methods are mainly used to generate test patterns for Device-Under-Test.  The functional test refers to typical testing,which means if you want to achieve high fault coverage,  you need to generate all the possible test patterns exhaustively.   And the number of  test patterns may become unacceptably Large.

Thus people thought other methods,based on fault modeling,  to generate LESS pattern while concurrently guarantee the high fault coverage. And the realization of  these method are often called Auto Test Pattern Generator.

Hope it is of some help.

zhangjirong

非常感谢您的帮助，麻烦您再帮我指教下，scan chain的scandatain和scandataout是否只能复用电路原有的端口，如果要自己添加端口，是不是只能自己手动在网表中添加。另外，我刚才做dft_drc时，报告error：can't find tmax32，请问这是个什么东东，是不是必需要用，否则无法完成scan chain，谢谢。

zhangjirong

非常感谢您的指教，小弟还想请教，在做scan chain时，自己添加的ScanDataIn和ScanDataOut，如何添加到电路中，是自己在网表中手动添加进去吗，还是工具可以自动添加，复用原端口和使用添加的端口有没有什么本质的区别。另外，刚才做dft_drc时，报告error: can't find tmax32，请问这是个什么东东，是不是一定需要这个玩意，请高人不吝赐教，再次感谢。

zhangjirong

另外请教，是不是因为功能测试不能完全测试电路内部所有节点有无缺陷，所以才提出了扫描链方法，增加电路内部节点的可控性和可观性？

waltjung

非常感谢您的帮助，麻烦您再帮我指教下，scan chain的scandatain和scandataout是否只能复用电路原有的端口， ...
zhangjirong 发表于 2014-1-14 16:49

                               
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  You are welcome to ask questions. The scan-in and scan-out typical should be mapping to the physical pins of package. However, to elevate the controbiliy and observably of SCAN, people usually insert PPI(Pseudo Primary Input) and PPO(Pseudo Primary Output) in Scan Chain. I am not sure if it is necessary to insert these PPIs and PPOs manually. Or it could be done with DFT tools provide by Mentor Graphic or Synopsys. When it comes to the error you mentioned, I am not sure what it is. But I assume it related to the tool you use. Since I have only use ATPG/DFT tools by my lab and has little experience with commercial tools, I could not answer your question.

You may need to look into the specific reference provide by the tool company.

Best

waltjung

另外请教，是不是因为功能测试不能完全测试电路内部所有节点有无缺陷，所以才提出了扫描链方法，增加电路内 ...
zhangjirong 发表于 2014-1-14 16:58

                               
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   Correct, you can think it in that way.

zhangjirong

还有一个问题请教，insert_dft时，dft是不是有专门的clock，而不是使用system_clock，reset是不是可以复用系统复位信号。ScanDataIn和ScanDataOut信号是不是可以复用功能端口，也可以额外添加端口。ScanEnable信号，我觉得不能复用功能端口，需要额外添加，但是添加的话，是做dft_insert的时候，工具自动添加呢，还是需要手动在原网表中加入呢，谢谢。

zhangjirong

做扫描链插入时，dft是不是有专门的clock，而不是复用系统时钟，reset信号是不是可以复用系统复位信号，ScanDataIn和ScanDataOut信号是不是既可以复用功能端口，也可以额外添加新的端口，如果是额外添加新端口，那么工具可以自动加入吗，还是需要手动在原网表中添加，ScanEnable信号，我觉得应该额外添加进去，不能复用功能端口，那么如何添加进去呢，是工具自动添加还是手动在原网表中添加呢，谢谢。

skjeon78

thans for good info