write default data in int EEprom

fuzzy · Joined: 26 Feb 2005 Posts: 64

HI,

I need to write 1 byte in my PIC internal eeprom only when i download firmware on my PIC. then my PIC must be able to change it forever during execution.something like a default password that can be changed.

how can i do it?

rwyoung · Joined: 12 Nov 2003 Posts: 563 Location: Lawrence, KS USA

If your programmer is also clearing the EEPROM (0xFF) then you could add code to your initialization routine to look for a 0xFF in the password locations, indicating they had been cleared. Then if it finds 0xFF, the PIC would re-write the default password.

Keep in mind that if you hard-code the default password into the firmware and don't set the read-protect bits, somebody might be able to work out your scheme by examining the extracted code.

Alternatively, depending on your programmer, you could specify a default EEPROM image to be loaded but that will probably require an extra step during programming.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Search the forum! It has been posted many, many times. You will use the #ROM statement. Something like this:

http://www.ccsinfo.com/forum/viewtopic.php?t=19607&start=1

Note that the location is different on some chips.

rwyoung · Joined: 12 Nov 2003 Posts: 563 Location: Lawrence, KS USA

Wasn't there a recent compiler issue where the #rom pragma wasn't working right. Something about the HEX file was screwed up and the eeprom data wasn't in the right place.

Or am I confusing multiple problems?
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!