IC Marking

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After looking in datasheets and forums, posting it as somehow I feel I need help from Atmel.

This post is not about the Code, but it's about the IC.

I am facing a typical problem.

With Basic Hardware remains same -

1. The ADC code to read ADC0 Channel works 100% ok with ATmega32-8PU.

2. But the reading are not stable when same is tested with ATmega32A-PU.

The current lot IC marking reads:
On Top Side -
ATmega32A-PU 1109
On bottom Side -
H6K752-2-354V2I
3-P1109 e3

Also another lot which has same problem with marking -
On Top Side -
ATmega32A-PU 1020
On bottom Side -
H34276-1-354V2I
5-P1020 e3

The Atmega32A-PU datasheet does not include any details about this marking.

Any inputs!!

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What are the fuses of the two chips set to?

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Atmel has info about their markings.....1109 and 1020 are manufacturing date codes.yy ww.
H6K752 I think is the manufacturing batch code.
2-354V2I could be the silicon revision...

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clawson wrote:
What are the fuses of the two chips set to?

hfuse = 0xd9
lfuse = 0xee

4MHz External Crystal
Vcc 5V

Worked even on Atmega32-16PU apart from ATmega32-8PU, but not on ATmega32A-PU

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I was simply asking you to confirm that BOTH chips had the fuses set identically. If two supposedly identical chips behave differently it's often that one does not have the same fuse setting as the other.

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Quote:
But the reading are not stable when same is tested with ATmega32A-PU.

Are the physical conditions same for both? What is the type of sensor you are using, proximity, temperature, etc? What is the approximate values that you get for both?

AVR Guide and Tutorials
http://maxembedded.wordpress.com

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I have a Hardware Board let's name it ABC,

1. m32-16PU pushed into it, flashed the program with fuse bits (as listed above), results ok. Reading ADC0 every 200ms and readings are stable. Room temperature does not change so often.

2. m32-8PU pushed into it, flashed the program with fuse bits (as listed above), results ok. Reading ADC0 every 200ms and readings are stable.

3. m32A-PU pushed into it, flashed the program with fuse bits (as listed above), results not ok. Reading ADC0 every 200ms and readings are unstable.

Hardware same, Programmer Same, Program Same, Fuse bits same, Supply voltage same, The only change is m32.

I will test to read other channel of m32A and will post back the outputs.

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Update -
Added 0.1uf cap between Aref & Gnd
Working perfectly fine.

Conclusion - Atmega32-8PU and ATmega32-16PU worked well without this cap, but Atmega32A-PU did not. Always follow datasheet....as it says "Internal 2.56V Voltage Reference with external capacitor at AREF pin" for REFS0:1