how to deal wiith memory bypass in DFT?

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drizzle

Joined: 07 Jun 2006
Posts: 56
Helped: 2

20 Apr 2007 9:49 memory bypass dft

hello all

when we do DFT coverage estimation,we should slove all the DRC viiolations first.
to memory logic,we usually set bypass mode or add some test logic like BIST.
now my problem lies in that i have no idea for memory drc vilolations and it is always be see as a black box.
i try to use some autofix commands in DFTC,the scripts i used as follows:

dft_drc
preview_dft -test_points all > reports / autofix.pts
insert_dft
dft_drc -coverage

using above script for memory bypass , the log show that u should set tdrc_activate variable true first. But i am so unlucky for no advanced DC tool in hand now. and DC version i used released in 2002,no XG mode.
after of all,there are solutions for DFT violations i dont know.
So,what should i do for the memory bypass using 2002 DC?
better to list some of the commands i should use

regards
drizzle

shiv_emf

Joined: 31 Aug 2005
Posts: 641
Helped: 16

29 Apr 2007 17:24 memoy bypass

dft_drc
preview_dft -test_points all > reports / autofix.pts
insert_dft
dft_drc -coverage

r u able to by pass using above commands ??

drizzle

Joined: 07 Jun 2006
Posts: 56
Helped: 2

09 May 2007 12:53 how to deal wiith memory bypass in DFT?

perhaps need sth more
but no dft_drc variable in 2002.05 DC
it is the problem

what's your opinion?
Smile

cheelgo

Joined: 23 Nov 2004
Posts: 84
Helped: 3

09 May 2007 13:06 how to deal wiith memory bypass in DFT?

the memeory bypass is somehow hard RTL code which need to be implemented in MBIST controller or wrapper.
how did you generate your MBIST?

drizzle

Joined: 07 Jun 2006
Posts: 56
Helped: 2

13 May 2007 3:41 how to deal wiith memory bypass in DFT?

i know if i want to test memory i must generate the MBIST
i just confused that weather bypassing the macro though adding some test points equal to generating the MBIST?

what should i do? help me please

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13 May 2007 3:41 Ads

naveenkrishnan

Joined: 14 May 2007
Posts: 16
Helped: 4

15 May 2007 14:49 Re: how to deal wiith memory bypass in DFT?

You probably will have to do this manually. Bypassing the macro is not equal to generating the MBIST, unless your MBIST tool takes care of adding the bypass mux in the wrapper.

http://vlsiforum.com

drizzle

Joined: 07 Jun 2006
Posts: 56
Helped: 2

17 May 2007 3:19 how to deal wiith memory bypass in DFT?

can anybody show me an example for concrete practice?

please
it is urgent for me

maybe i should find more advance DC Smile

dft_guy

Joined: 19 Oct 2006
Posts: 114
Helped: 14
Location: USA

17 May 2007 5:11 Re: how to deal wiith memory bypass in DFT?

Drizzle:

From the posts, it's not clear what you need. But I can tell you for sure that DC will not create MBIST for you, or a bypass. If you do generate BIST, it'll be from a tool such as is available from Mentor, LogicVision, and a handful of other companies. I believe that Synopsys has (or had) some DesignWare BIST macros, also.

Normally you can choose to put in a bypass when generating BIST logic.

However, if you're not BISTing your memory, you can code your bypass into RTL as has been suggested. You need to mux the memory inputs and outputs, with the inputs being selected during scan mode. For the best fault coverage, also combine the address and enable signals with the input data using some some xor gates.

Hope that helps
John
DFT Digest

drizzle

Joined: 07 Jun 2006
Posts: 56
Helped: 2

17 May 2007 11:05 how to deal wiith memory bypass in DFT?

thanks dft_guy

u r always show me the valubale advice which make me clear about what should i do next.

now i have mentor dft tools in hand, just need some practice for the memory bypass.
i will try to grope for proceeding the project in term of changing code although i was not the initial code writer.

thanks dft_duy
thanks everybody

best regards
drizzle