ISP erases EEPROM

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When I use ISP to program a new bootloader in my megaxx9 chips, the eeprom gets erased. Is that normal, or am I doing something wrong?

I use ButtLoad in a Butterfly as the ISP programmer. I've used AVR Studio, and I've used AvrDude, and in both cases the EEPROM got erased.

While on the subject, actually everything gets erased. So when I install a bootloader, the application program gets erased. That's not a problem as I can reload it with the bootloader.

And if I should try loading an application program on the xx9 chip using ISP, the bootloader gets erased. I can live with that too. All I have to do is remember to not load an application program using ISP. Of course I forget, but as soon as I discover the bootloader is gone, I suddenly remember not to do that all over again :)

It's the EEPROM erase that's the pain in the backside.

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steve17 wrote:
When I use ISP to program a new bootloader in my megaxx9 chips, the eeprom gets erased. Is that normal, or am I doing something wrong?
It's normal.
There is a fuse setting that will change that.

Iluvatar is the better part of Valar.

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You are getting a 'chip erase' from your ISP app, which erases flash AND eeprom UNLESS EESAVE is programmed.

So, program EESAVE.

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Thanks guys. I just tried it and it works!!

Hopefully that's the last time I will have to re-program the EEPROM.