Was '[sdiy] FPGA Synth Music' - Damaging FPGA by an Incorrect UCF Setting ?????

[Scott Gravenhorst]

Eric Brombaugh <ebrombaugh1 at cox.net> wrote:
>The condition you specified is the one they describe.
>
>In the reverse situation where the bitstream is compiled with a 
>non-default setting of 3.3V but VCCAUX is actually 2.5 volts, I assume 
>that the threshold setting would be ~25% lower than described in the 
>datasheet, so the logic levels would have slightly lower noise margin.
>
>Eric

Thank you Eric,

I'm satisfied that I'm OK making the usual bone headed errors I do.  I can easily understand
that the design may not function correctly with incorrect settings, my main concern was the
idea of permanent physical damage, but that has been thankfully allayed.

I shall now return to making bone headed errors...  (c:


>On 03/02/2010 09:27 AM, cheater cheater wrote:
>> What if you set it to 2.5 while the input is 3.3?
>>
>> D.
>>
>> On Tue, Mar 2, 2010 at 17:15, Eric Brombaugh<ebrombaugh1 at cox.net>  wrote:
>>> On 03/02/2010 07:12 AM, Scott Gravenhorst wrote:
>>>>
>>>> I am hopeful that Xilinx designed their FPGAs so that a simple goofed up
>>>> UCF can't
>>>> actually blow out or physically damage the FPGA...
>>>>
>>>> Do I have reason to be concerned?
>>>
>>> OK, just to be sure this horse is _really_ dead, let's dig into this.
>>>
>>> The configuration option is:
>>>
>>> CONFIG VCCAUX="value";
>>> Where value is 2.5 or 3.3
>>> Example:
>>> CONFIG VCCAUX=3.3;
>>>
>>> Xilinx describes this further here:
>>>
>>> http://www.xilinx.com/support/answers/31375.htm
>>>
>>> As far as damage, they say:
>>>
>>> "If the CONFIG VCCAUX constraint is not set and a user chooses to change
>>> VCCAUX voltage to 3.3V instead of the default 2.5V, there could be problems
>>> with the threshold levels on the inputs. This should not cause any damage to
>>> the device, but the inputs to the device might not meet the higher threshold
>>> requirements, so there might be logic failures in your design."
>>>
>>> So, no, you won't hurt the device.
>>>
>>> They're a lot more careful about these things today. I can remember back on
>>> the '2000 and '3000 series parts in the early '90s it was possible to build
>>> a pathological bitstream that could cook the parts. You really have to work
>>> hard to do that these days.
>>>
>>> Eric
>>> _______________________________________________
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>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>
>>
>
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-- ScottG
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-- Scott Gravenhorst
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