S Parkis wrote:
>
> In putting together a simple '16F877 programming system I've run into
> a puzzling problem.  The system programs the device directly (i.e.,
> not a bootloader arrangement) via LVP as described in DS39025E,
> "PIC16F87X EEPROM Memory Programming Specification".
>
> Here's the situation.  If I program the user program memory space,
> followed by the configuration memory and finally the data EEPROM
> memory, the data EEPROM doesn't "take".  It seems to read back OK
> while in programming mode, but it's not really there where I meant
> to put it--it must have been written to and read back from some
> other memory location.  (I know it's not there because the
> application program doesn't find it where expected).  After
> programming the configuration memory I pulse MCLR* before using the
> data EEPROM load and read commands, thinking this will cause the
> data to be stored from the beginning of the data EEPROM.
>
> If I load the data EEPROM memory first right after entering the
> programming mode, then the user program memory and then the
> configuration memory, all works OK.  This is a viable solution to the
> problem but I'd sure like to know why the other technique fails.
>
> Has anyone already cracked this nut?
>
> Thanks,
>
> Steve

Try programming the chip in this order...

  ROM
  EEPROM
  CONFIG

You may be enabling code protection and thus disabling EEPROM writes.

--
Best regards

Tony

mICros
http://www.bubblesoftonline.com
mailto:sales@bubblesoftonline.com

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