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[SOLVED] General question on EEPROM of PIC Microcontroller

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prmurthy

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Hi everybody,

Can somebody tell me about internal eeprom of PIC microcontroller. I have a very basic doubt weather the eeprom is written on defined locations of eeprom or it writes on all locations of eeprom.

Thank you
 

wp100

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Hi,

EEprom is typically located at adddress 0x2100.

What is written to and read from eeprom is entirely down to the code you write.

As far as I know it will write to just one single location if so instructed, it does not apprear to rewrite/ refesh all other locations when doing so.
See the datasheet eeprom electrical specifications where it discusses the need to refresh the data as a separate issue.
 

prmurthy

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Hi,
Thank you for reply. Yes I have seen that I have few data on the first 2 lines but the rest is filled with zeros. If you look at brand new chip it will be filled with something like 3FFF at all locations. This made me to think on this question weather it writes on location or only those defined.

Thank you

Sorry the program memory is filled 3FFF and eeprom memory is filled with FF. Does this means that FF is blank??
 

wp100

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Hi,

Opps - had just amended my previous answer .. when you replied.
 

prmurthy

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Thank you

Which means I can use the other locations if the first locations are corrupted ??
 

wp100

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Hi,

If your eeprom data is corrupt you should be able to rewite it to the same locations.

If the locations are damaged then you may be able to use other locations.; depending on how bad the damage is.

In general use I think its very reliable.

Some time ago I did a read / write test on the eeprom of a 16F876A to prove it would be reliable for my project - I repeatedly wrote to then verified of the whole eeprom area, took a couple of weeks to do that, it was only after 500,000 write that I had one byte fail.
The byte of memory was defective, not just corrupt, but all other locations were still usable.
In practice it mean my project could backup key paramenters for 10 years with little chance of failure, which is probably more than the expected life of the whole pic chip.
 

yadavvlsi

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You can specify in which area you want to write code. You can use rest of area during operation. The data EEPROM and Flash program memory is readable and writable during normal operation. This memory is not directly mapped in the register file space. Instead, it is indirectly addressed through the Special Function Registers.
PIC microcontroller memory organization tutorial
 

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