Internal eeprom acces with Atmega16

I have a problem with using the internal eeprom of the atmega16. I am
using codevision C and in the help file they say to do something like
this :

//declare global
eeprom a=0;

then then you can write  the eeprom with changing the value for a , the
eeprom adress is the adress the compiler has given  soo you should not
worry about that.

but this doesnt work, in my opinion due that every time you restart
your system the eeprom is erased and get the inital value of 0 due to
the global declaration. They claim that this initial value is only been
given when programming the atmega if i understand correctly, anyone
exprience with this?


Thanks

Yannick

> //declare global
> eeprom a=0;
>
> then then you can write  the eeprom with changing the value for a , the
> eeprom adress is the adress the compiler has given  soo you should not
> worry about that.

I don't use this toolchain. However, I imagine what this really does
is:

1. declare a temporary RAM variable 'a'.

2. declare an EEPROM value 'a' which is loaded with your initializer
value. When you flash new code into the chip, as long as you haven't
disabled this functionality, the EEPROM will be erased and reloaded.
Programming the EEPROM area might be a separate step depending on your
programming software (AVR Studio for instance it's a separate step -
also for the various command-line utilities such as uisp, avrdude, and
so forth).

3. implement some bizarre functionality underlying the RAM copy of a
which reads it and writes it from EEPROM when accessed at runtime.

I'd be very leery of something this "smart".

The best place to ask this question is the CodeVision support forum on
Yahoo.

Ken
www.speechchips.com

Hi,

I think you should read the EEPROM section in the datasheet for the Mega 16.

There is an example.

Regards Jens

"Yannick" <yannick_de_wit@pandora.be> skrev i en meddelelse 
news:1142357589.285303.248370@j52g2000cwj.googlegroups.com...
>I have a problem with using the internal eeprom of the atmega16. I am
> using codevision C and in the help file they say to do something like
> this :
>
> //declare global
> eeprom a=0;
>
> then then you can write  the eeprom with changing the value for a , the
> eeprom adress is the adress the compiler has given  soo you should not
> worry about that.
>
> but this doesnt work, in my opinion due that every time you restart
> your system the eeprom is erased and get the inital value of 0 due to
> the global declaration. They claim that this initial value is only been
> given when programming the atmega if i understand correctly, anyone
> exprience with this?
>
>
> Thanks
>
> Yannick
> 

Yes there is, for programming the eeprom externally electrical , but
not how to do it internally with codevision C... maybe i just should do
it in assembler but wanted to do it with the codevision code as this
would be much easier...

Yannick wrote:
> Yes there is, for programming the eeprom externally electrical , but
> not how to do it internally with codevision C... maybe i just should do
> it in assembler but wanted to do it with the codevision code as this
> would be much easier...
> 

Did you REALLY read the data sheet?

Get Atmel document doc2466.pdf from the Atmel Web pages and read
pages 16 to 20 again.

-- 

Tauno Voipio
tauno voipio (at) iki fi

You are right,  but it was confusing because they do not mention these
pages in the table of contents for eeprom, if you see in the table of
contents for programming memory you get to page 150 or something and
there it is for externally program the memory... but yes indeed at page
16-20 it is described very well, it works perfect now... i had to look
better, thanks for giving me the good pages:)

Yannick