Re: X4000 bad configuration

Here are the details:
All plastic easily absorbs moisture.
When such a plastic package is suddenly heated up (chips used to be run
straight through a solder bath), then the internal steam can blow up
the package.
Conscientious manufacturers, therefore, bake plastic parts for hours,
before they solder them on the board (unless the chips come directly
out of a moisture-controlled environment.)
This is all pretty common practice, definitely not Xilinx-specific.
Peter Alfke (from home)
========================
David Ashley wrote:
> Hal Murray wrote:
> >...
> > Is there a mechanism to make a whole batch of chips go bad
> > without visible damage?  I'm assuming idiot or short cuts
> > rather than malicious.  The sort of thing that would happen
> > in a startup about to go under.
>
> I thought I read Peter mention something about humidity --
> if the humidity isn't kept right during storage, something
> bad can happen to the pads, so when the part is soldered
> down to a PCB something won't be right...or something.
>
> -Dave
>
> --
> David Ashley                http://www.xdr.com/dash
> Embedded linux, device drivers, system architecture

Two more ideas:
1=2E
Look at the CCLK signal integrity (double edges)
2=2E
You might append a few extra bytes of all-ones to the very beginning
and the very end of the bitstream, without changing anything else.

But, checking Dout would find all these problems anyhow.
It is unbeatable as an analysis tool.
Fixing the problem is then another matter.
Peter Alfke
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Peter Alfke wrote:
> I still remember what we used to suggest 10 years ago:
>
> Look at the Dout pin. There, the serial bitstream is passed on to the
> next device, but only after the device otself has received its
> configuration.
> So you should see the preamble' length count etc, and then a continuous
> High level, until the end of the internal configuration. And then the
> remainder of the concatenated bitstream is passed on to the next
> device.
>
> You have one advantage: You have a working board. So poke around on
> CCLK and Dout-Din-Dout and observe the traffic, and compare the boards.
> You claim that these should be identical devices (although Xilinx made
> several different sub-families, they are clearly marked)
> There is still the possibility that you bought grey-market or bogus
> parts. Do you know the source?
>
> Bon chance (isn't that what they say?)
> Peter Alfke, from home.
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> Jacques GENIN wrote:
> > Peter Alfke a =E9crit :
> > > I think it's time for you to describe the "badness".
> > > The thread gets a bit long in the tooth. :-(
> > > Peter Alfke
> > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > I designed a PCI board with 3 XC4010E on it
> > (PCI with AMCC part, not in FPGA).
> > The first FPGA is configured asynchronous peripheral.
> > The other FPGA are daisy chained and configured slave
> > peripheral (cf. Data book p. 4-74).
> > During ten years, I had had no problem with that design.
> > Since the beginning of this year, as XC4010 is a
> > discontinued part, I buy it more and more often from brokers.
> > I got three deliveries of "bad" parts.
> > Using those "bad" parts, configuration pins M0, M1, M2, if
> > left floating, do not all polarize high as they should,
> > because of internal pull-ups. Then, the parts do not enter
> > the configuration mode implied by my design.
> > If I set external pull-ups, configuration pins polarize
> > correctly and configuration process seems to be successful,
> > but the behaviour of the part is wrong, ie my board does not
> > work. I did not investigate much at this time, but the pins
> > seem to remain floating and the parts do not start working.
> > Though, these "bad" parts are not counterfeits, as would be
> > empty cases, because configuration process progresses
> > correctly : DONE raises on time, with no external pull-ups,
> > parts may enter master serial with address pins toggling.
> >
> > The only difference is that "good" parts had mainly been
> > delivered in sticks and "bad" parts had always been delivered
> > in tapes.
> >
> > Further, "bad" parts were recent, but seemed older
> > (oxyded pins).
> >
> > I'd like to know whether someone else experienced same
> > problem.
> >=20
> > Jacques GENIN