stored variables

Earl Foster

I am trying to read/write a variable from/to a specific memory location that will be retained when there is a power cycle or reset.· The variables will change throughout the life of the program so I figure I can assign a seed value the first time and then read and write the changing·variable there after.· What is the best approach to accomplish this task?



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ericball

If you want the variable to survive a Propeller power down or reset, you're going to have to store it in an off-chip EEPROM or equivalent.

Beau Schwabe

Earl Foster,

Andy Lindsay wrote an excellent description on how to do this very thing. The only caveat is that if you re-program from the Propeller IDE, then the EEPROM locations value will be lost. But even then if you substitute a larger EEPROM and write to the upper 32K then even a Propeller IDE download can't touch this area of EEPROM ... only the EEPROM object within the Propeller can see it.


Check out this link Andy Lindsay wrote:
http://forums.parallax.com/forums/default.aspx?f=25&m=219237

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 3/28/2009 5:49:56 AM GMT

Earl Foster

Thanks, I figured there was a way. I will look into that thread.

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"Don't ask yourself what the world needs - ask yourself what makes you come alive, and then go do it." - H.T.Whitman

mpark

Beau, which part of the text you quoted isn't exactly true?

Beau Schwabe

mpark,

I apologize... I misread your post. For some reason the "...off-chip EEPROM or equivalent" didn't register with "...surviving a Propeller power down or reset".

I edited my earlier post

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

mpark

You weren't quoting me so you needn't apologize to me. I was just wondering if I was missing something. Thanks for clearing that up.

ericball

Actually, you make a good point. Since the IDE can overwrite the low 32K of the boot EEPROM, using that space for temporary storage is not ideal.

Earl Foster

Well it worked like a champ. Thanks

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"Don't ask yourself what the world needs - ask yourself what makes you come alive, and then go do it." - H.T.Whitman