This was a design problem with a 5000-series Xylinx device. Nobody had
caught it before my client, probably 'cause he used more of the available
gates than most folks did. The gate was supposed to be connected internally
to a pullup, but in fact was floating. All of the parts purchased,
regardless of lot number, acted the same way.

It was very hard to prove that Xylinx was at fault, but I did. Although I
got the part to "work", my client didn't trust 'em anymore, and Xylinx
swapped several thousand devices at $9 USD ea for 7000-series parts (which
didn't have the bug). This was about 7 yrs ago. The reason I am so
suspicious of large gate arrays is just that- it is very hard to be certain
that the array will work for every possible way it can be connected up.

I don't have this concern with PICs or other microprocessors because the
interconnections are FIXED, and therefore are capable of being tested fully
on a functional high-speed tester, at least on a batch basis. Yes, we
occasionally DO find bugs with PIC parts as they become increasingly more
complex, but it doesn't take 6 weeks of agony to locate the problem...

--Bob

At 03:25 PM 11/17/2003, you wrote:
>Bob Axtell wrote :
>
> > Theoretically CPLD are marvelous devices, but when there is a problem
> > inside, physically  moving San Francisco a foot further to the left is
> > easier...
>
>
>
>Theoretically PICs are marvelous devices, but when there is a problem
>inside, physically moving San Francisco a foot further to the left is
>easier...
>
>Or replace "PICs" with just about anything...
>
>Or is this a know problem with CPLD's *specificaly*.
>
>Jan-Erik.
>
>--
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--------------
Bob Axtell
PIC Hardware & Firmware Dev
Tucson, AZ
1-520-219-2363
"I lose some on each sale but make it up in volume."

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