Jumping to conclusions?  You bet!  Not a production programmer?  Right=20
again!  Not proof?  You're batting 1.000!

I'm as fallible as the next guy,  so it's possible I made a mistake.  I=20
took as much care as time permitted and reached a conclusion, knowing=20
full well that it might not be the RIGHT conclusion.  If you never have=20
to do that, you are a lucky man.

I've never had a problem with MicroChip parts before or after that=20
incident.  I've also never used free samples before or after.  I've=20
never had a problem with the programmer, nor have any of the field=20
service personnel who use them.  The software reads back and displays=20
the configuration word.  I compared it to the desired value.  It also=20
reads back each programmed byte and compares it to what was sent, and=20
displays an error if they differ.  The resonators were tested in my=20
16F877 test bed (also "not professional").  Does any of this constitute=20
proof of bad samples from MicroChip?  Nope, it's just anecdotal=20
evidence, to be taken for what it's worth.  I never claimed otherwise.

Kerry


Olin Lathrop wrote:
> Kerry Wentworth wrote:
>  =20
>> The customer got 6
>> free samples of  16F877As in the 44 pin SM package.  I designed a PC
>> board and built 6, using 20MHz ceramic resonators with built-in caps,
>> as I normally do.
>> ...
>> After exhaustive testing without results, I replaced a 20MHz resonator
>> with a 4MHz resonator, and it suddenly worked.  An 8MHz resonator also
>> worked.  But not a 20!  The leads for the resonator were as short as
>> practical, as I have had trouble at 20MHz if the leads are too long.
>>
>> At the time, that was all the proof I needed.  If you need more, I can
>> always send you a couple of the chips and a copy of the artwork.  I
>> don't think it is worth the effort, and my point is "Be aware that
>> free samples may not be prime parts".
>>    =20
>
> You are jumping to conclusions, which further erodes your credibility.  Y=
our
> evidence is hardly proof for the conclusion that "free samples may not be
> prime parts".  I seriously doubt that Microchip bins slightly out of spec
> parts to be sent out as free samples.  That would defeat their purpose, a=
nd
> would cost more in logistics.
>
> A more likely possibility is that you got a bad batch of 20MHz resonators=
,
> or they were weak to begin with.  Resonators are usually weaker than
> crystals, and 20MHz is on the high end for resonators.  Did you try with =
a
> ordinary 20MHz crystal or a different model of resonator?  Did you look a=
t
> the resonator specs carefully?
>
> Another possibility is that you had a bug such that XT instead of HS
> oscillator mode was selected.  That will work at lower frequencies, but f=
ail
> at higher, just like you saw.  You were using a "less than professional"
> programmer to begin with, and then modified its code on top of that, so d=
o
> you really know the oscillator setting was set in the PIC as it was inten=
ded
> in the code?  Did you actually read back the config word to check?
>
> Also I suspect this programmer you used wasn't a production programmer in
> that it didn't read back at the Vdd limits.  That matters for older parts
> like the 16F877.  I don't remember whether it applies to the A version, b=
ut
> I would do the double readback unless it explicitly said it wasn't needed=
..
> How do you know your flakeware programmer didn't cut short the programmin=
g
> time or something, and the bits weren't really all there?
>
> In short, it's far more likely you screwed up in any of several way rathe=
r
> than you got bad PICs as samples.  Your jumping to conclusions when other
> more likely explanations are possible makes it difficult to trust your ot=
her
> conclusions, such as that your testing was "exhaustive".  Most likely you
> missed something, probably one of the things I mentioned above.
>
>
> ********************************************************************
> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
> (978) 742-9014.  Gold level PIC consultants since 2000.
>  =20



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