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Old 02-18-2005, 10:25 PM
Vladislav Muravin
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Default Re: Issues with a batch of Virtex-II chips

Igor,

Vow, this is very similar to what i have experienced a couple of days ago.
I did not try, however, to look for different "batch"s, as you did, because
i think that all of our FPGAs
are XC2V2000/3000 676AGT0405, i think.

So in my design, i am cascading 4 DCMs.
But i am not using their LOCK indication, because i am only interested in
some large fractional M/N frequency synthesis,
and the input frequency is less than 24 MHz
( I assume that you are not using any DCM outputs for input clock less than
24 MHz)

The problem was that the last DCM was not generating the desired frequency,
but exactly either 1/8 or 1/16 of it.
It was looking like the reset was applied for too short period of time (but
it was for more than 3-4 input clocks!)

So this problem was resolved by defining a reset registers for each PLL, and
asserting/deasserting the reset by the software (or some delay implemented
in FPGA by some large counter) in chain.

I assume this is this is different from what you've experienced, but hope
this helps.

Sincerely,



Vladislav Muravin

Senior FPGA Design Engineer

Advantech AMT (Advanced Microwave Technologies)

657 Orly Avenue

Dorval H9P 1G1

Quebec, Canada

Tel: (514) 420-0045 ext. 240

Fax: (514) 420-0073

http://www.advantechamt.com





Finally, i noted that

"IgI" <[email protected]> wrote in message
news:[email protected]
> Hi!
>
> I'm using Virtex-II (XC2V1000-FF896-4C) in one of the product which we

have
> been selling for over 3 years. Recently we got "new" batch of Virtex-II
> chips and problems started to arise. So far I have isolated PCBs with

three
> different batch of Virtex-II chips:
>
> Batch A:
> XC2V1000
> FF896AFT0301
> F1247582A
> 4C
> Philippines
>
> Batch B:
> XC2V1000
> FF896AGT0409
> D2169507A
> 4C
> Taiwan
>
> Batch C:
> XC2V1000
> FF896AFT0205
> F1205613A
> 4C
> Philippines
>
> All the chips in batch A have the suffix AFT301, all the chips in batch B
> have the suffix AGT0409,...
> PCBs with chips from batch B and C are working fine, on the other hand

none
> of the 42 PCBs, where chips from batch A are used are working. PCBs are

the
> same (same revision) for all the products, all other components (ZBTRAMs,
> DDR SDRAMS, passive components,....) are the same. All voltages are within
> the safe margins, all input clocks are clean. All the affected boards pass
> the JTAG test, in other words we didn't find any soldering errors, short
> circuits, vias without metallization, wrong resistors or capacitors,
> incorrectly oriented diodes or capacitors... or any other error we could
> think of. We got all the chips in a sealed package. PCBs were tested at
> different temperatures (from 8 degrees Celsius to 46). Only the PCBs with
> chips from batch A don't work. Let me explain what precisely is not

working.
>
> I'm using 6 DCMs to generate clocks for ZBTRAM, DDR, System,

ConfigBus,...
> and two DCMs don't set the locked signal after I release them sequentially
> from reset. I don't know if other parts of the design (the parts which

don't
> use ZBTRAM clock) don't work either, because the missing clock is a fatal
> error and I didn't have the time to investigate further in that direction.
> Working freq. of ZBTRAM is 120MHz, DDR is working at 166MHz, System at
> 100MHz, ConfigBus at 10MHz,...
>
> We are currently using ISE 5.2 SP3 for this design. I have verified the

bit
> stream by reading it back from the chip and it's ok.
> Two coworkers, guys from the production and I are working on solving this
> problem for the last two days and we are almost out of ideas what else we
> could try, except replace the problematic chips with the non-problematic.

I
> can't use ISE 6.1 or newer because the routing is not successful or ISE
> simply doesn't meet the timing constraints (the chip is 99% full).
>
> Have you experienced anything similar in the past? How did you solve the
> problem? Do you have any ideas/suggestions what else I could try? I

couldn't
> find any document on the xilinx web site explaining the detailed chip
> signatures. I would like to know, what AFT0301 stands for? Is this the
> product date, production line, factory code...? I would like to know, when
> the chips have been manufactured (how old are they)?
>
> I guess we'll have a competition in the company next week. And the goal

will
> be; who can throw virtex-II the farthest... Ok, I'm just joking, but I
> needed to vent...argh...
>
>
> Igor Bizjak
>
>



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