Try it tomorrow again !
I've seen this kind of behaviour with JDM programmer and 16F628,
after reprogramming it for about 10 or 20 times within a few hours,
I had to wait one day to get access to these PICs again.
But I guess I'm about the only one in the whole world who has seen this 
fantastic phenomena ;-)
Stef Mientki

PicDude wrote:

>Spent a bunch of time today trying to program a few different devices but ran 
>into some walls.  First up was a 16F818 which programmed successfully only a 
>few times, intermittently.  Two fresh F819s did the same.  Google and other 
>resources told me that the F818/9 are funny animals w.r.t. programming, but 
>trying all the suggestions I could find, it still did not work.  I tried 
>these with a quickly-hacked-together JDM clone with IC-Prog, and a commercial 
>ICD2 clone with MPLAB 7.30.  FWIW, both of those programmers can successfully 
>program 16F872's and 16F628's, so I trust that the programmers work.
>
>So I took a break from that and switched to another chip -- the 16F88.  With 
>the ICD2 & MPLAB, I was able to successfully program this device, with MCLRE 
>on (serving as a reset pin).  When I changed MCLRE to off, programming 
>failed.  Since that, the programmer fails to recognize the 16F88's device ID 
>anymore and fails programming.  Google found me some info that indicated 
>newer PICs can get locked up in this way and un-reprogrammable when both 
>internal-oscillator and MCLR-as-IO was selected, but I had been using the 
>external RC oscillator config setting throughout all of this.  I had another 
>fresh 16F88, but it did the same thing -- after changing the config bits in 
>the code to use MCLR as a reset pin, it won't re-program.
>
>Arrrggghhh!!! I'm stumped, and frustrated.
>
>So my questions -- if some PIC's require Vdd-before-Vpp, why doesn't the ICD2 
>control Vdd?  Are the 16F819 and 16F88 really Vdd-before-Vpp devices?  I've 
>never really read-thru any programming specs before, but maybe I'll check one 
>out.
>
>Most importantly is what I can do at this point, and is there really a 
>programmer that properly supports the 16F818 and 16F88?  From some research, 
>the F88 should be easy, but I'm not sure why it locked up.  The F819 appears 
>to be problematic, but there must be a supported programming HW/SW combo that 
>works for this, right?
>
>Cheers,
>-Neil.
>
>
>
>
>
>  
>
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