On Thu, 09 Jul 2009 16:09:51 -0400, you wrote:

>At 02:13 PM 09/07/2009, you wrote:
>>On Wed, 8 Jul 2009 20:03:02 +0800, Xiaofan wrote:
>>
>> >If you compare MCV14A with PIC16F526, you may find them
>> >almost exactly the same (less packaging option)
>> >http://ww1.microchip.com/downloads/en/DeviceDoc/41326B.pdf
>>
>>When you compare the characteristic specifications the MCV14A has a few
>>that are looser and has no FLASH endurance specification.
>>
>>IMO they are functional reject PICs or 'toy' parts. Is the term 'toy' sti=
ll
>>used?
>>
>>I don't really see customer testing the parts, Microchip already tested
>>them to reject them (unless maybe they reject whole wafers but would they
>>package any untested die?).
>
>The customer will test a complete module or complete product with the part
>installed, meaning if the micro fails at, say, temperatures above  63=B0C
>at maximum clock speed, so might the product (or perhaps not because the
>designer has chosen a more conservative clock speed).

Yes they will (probably) test the whole product but would it make financial
sense to scrap or rework the whole product for processor failures which
were not detected because they didn't pay Microchip enough to test them? I
don't buy that. =


>I doubt that these are 'rejects', merely not tested as thoroughly or to
>as high standards (for use in consumer gadgets, toys and other disposable
>stuff where a 1% overall failure rate is not fatal).

They test the chip, if the measured parameters are good enough  it gets
PIC16F526E stamped on it. If they are not so good it gets PIC16F526I
stamped on it. If it is worse again it gets MCV14A stamped on it. =


A PIC16F526I is a reject PIC16F526E and an MCV14A a reject PIC16F526I. If
they make mostly very good chips they can stamp whatever number customers
want to buy on them (as long as the cheapest ones still show a profit). =


I used to work for TI (long time ago). Transistors got graded into voltage
and/or Hfe ranges and were marked with the appropriate part number.
Transistors that didn't meet the lowest specification but still worked a
bit got some strange number stamped on them and were sold by the bucket to
Hong Kong or somewhere to make toys from hence the 'toy part' description. =


The point I am making is they were all tested and sold cheap because they
were junk not because they left the testing up to the buyer. =


-- =

http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist