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[f-cpu] Teste



Bist will never be enought. scan path is used to
propagated teste (to find stuck-at-one and
stuck-at-zero fault) in every corner of the chip.
It's almost impossible to cover all case from the
outside, to have a cover of 95 % you will need 10^9
pattern or even more, it will take days to teste a
cpu and the BIST will be bigger than the core !

-----Message d'origine-----
De: whygee@club-internet.fr
A: f-cpu@seul.org
Date: 14/02/02
Objet: test (was: Re: Rep:Re: Re: [f-cpu] No latches,
please !)

hi nicO !

>That's not crazy it's called multiphased logic.
my second name is "reinvent the wheel" ;-)

> You could use 2 or 4 clock phased to synchronise
things
>but i imagine what a nightmarre it could be to debug
>and to test.

Concerning the test, remember that there is a BIST
unit that
takes control of the whole datapath and takes care to
test
all the execution units and the memory arrays. If the
"latch"
(those you like and/or those you don't) is in the
datapath,
it -will- be tested. Those that can't be tested
without complex
stuff will use a classical scanpath but the scan
chain will be
kept as short as possible.
By the way, one of the optional units (popcount) will
certainly
be used for signature compaction.

How much do i have to emphasize on this ?
Yes, this will be custom-designed test but
 - we don't need ATPG
 - we couldn't afford it anyway
 - always trust your nose and make meaningful
measurements.

>nicO
YG

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