Difference 12c674 12ce674

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Hi NG,

does anyone know whats the difference between these two PIC
processors. I can't find any info about the 12c674 on Microchip's
website, but i have both of these....
There must be a difference in the configuration word, since 12ce...
programs correctly, but 12c... programs, but is codeprotected
afterwards.

BTW: the missing "e" 12c674 might imply that the 12c674 does not
have EEPROM memory on chip, but in fact it has, and it's working!

Thanks a lot,
Wolfgang

Re: Difference 12c674 12ce674
Hi Ben,

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No, it isn't.

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Sorry, should have mentioned i talking about windowed devices....

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My programmer complains about not erased devices.

Thanks,
Wolfgang

Re: Difference 12c674 12ce674

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You need to erase the device with a UV eraser.
see google "UV eraser"
The CE just means it has EEPROM, make sure you save
the Oscillator Calibration Value before you erase it!!

Phil





Re: Difference 12c674 12ce674
Hi Phil,

 
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Sorry Phil, you missed the point.

I have two chips, one 12C674 and one 12CE674, both in windowed DIP
package. Programming works fine with the CE type, the C can be
programmed and verified, but as soon as the configuration word is
programmed, the device is code protected.
Thats why I think, there must be a difference in the config bits.

Both devices definitely *have* EEPROM on chip.
I tried to access it (it works fine on both), and on the windowed
devices you can actually *see* the extra chip through the window.

The Microchip Homepage does not show a 12C674 type, only 12CE674.

Greetz,
Wolfgang

Re: Difference 12c674 12ce674

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For a resistor, if it doesn't fit within the 1%tolerance, it goes into the
2%, and if it fails the 2% it goes into the cheaper 5% bin.

For a CPU, if it fails to run at 8mhz, it may qualify okay as a 4mhz CPU.

The C and CE may be the same, but the C did not meet all the specs of the
CE, therefore it got downgraded to only qualifying as C.

This is just a reasonable guess so don't take it as fact.  ;-)


Re: Difference 12c674 12ce674
Hi Amused :-)

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OK, but then Microchip would list these device numbers, wouldn't they?

Greetz,
Wolfgang

Re: Difference 12c674 12ce674
Hi Clint,

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Hmm I recall that behaviour on some old 16C74.

On that 12C674, after UV erasure all program memory bytes read FF
and after programming ONLY the program memory, I CAN read back the
correct code. It is only after setting the config word, that all bytes
read as 00.
Very weird. Maybe this chip is defective anyway.

Thanks,
Wolfgang

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