On Mon, 31 Mar 2008, Richard Seriani, Sr. wrote:
> Using external programmer, PIC 16f88 programs without problem the first 
> time. After that, programming errors crop up and the device seems to not be 
> able to be reprogrammed.
> 
> I noticed the user had !MCLR set as I/O and was using the internal 
> oscillator. I vaguely recall something reading somewhere about this causing 
> the problem. I got a few google hits searching on MCLR and 16f88, but 
> looking for more explanation. I haven't been able to find anything on the 
> Microchip site.

I just struggled with this for several days too.  Very frustrating!

Here is a post on how to fix those unreprogrammable PICs.

  http://forum.microchip.com/fb.aspx?m=306403

It seems that the 16F88 and a few other chips become unprogrammable if you 
use MCLR as an IO pin, you use the internal osc, and you set TIMER1 to use 
the internal osc as a clock source.  The above link gives a fix to recover 
the part.

--
Ian Smith
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