In case somebody else makes the same goof, here's what I finally
figured out.  To enter/re-enter programming/verify mode, apply the
following sequence:

mclr*  rb.3   rb.6   rb.7
 L      L      L      L
 L      H      L      L
 H      H      L      L

Once in the programming/verify mode and in configuration memory, the
complete sequence must be accomplished again in order to (re-)access
user program or data EEPROM memory.  This is clearer in the
programming document's timing diagrams than in the textual
description.  My mistake was in simply pulsing mclr* while leaving
rb.3 high to escape configuration memory, rather than lowering and
raising rb.3 while mclr* was re-asserted.

I can now send the image in the logical memory-mapped order--code,
configuration, eeprom--successfully.

Thanks to Tony and Alan for your suggestions.

Regards,

Steve

On  3 Feb 02 at 21:31, 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...

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu