James,
I really don't know what you problem is and I have no time to guess or wo=
rk
around your problem, but have you tried errata=92s pdfs?

http://ww1.microchip.com/downloads/en/DeviceDoc/80212D.pdf

I think this is the last on 818/9

Regards,
Dennis Crawley

----- Original Message -----
From: "James Alston" <jamesa@jpacsoft.com>
To: <piclist@mit.edu>
Sent: Thursday, September 23, 2004 7:07 AM
Subject: [PIC:] Can't reprogram 16LF819 in-circuit


> Does anyone know of any issues that might be preventing some PIC16LF819=
's
> being reprogammed in-circuit, using a Microchip ICD2 programmer?
>
> I have 20 boards each with a PIC16LF819 (SOIC) soldered in. They all
> programmed without any problems first time around. I then needed to
> reprogram them and 17 reprogrammed fine, but 3 failed. In fact they fai=
l
at
> the first of the programming cycle, the Part Erase. Even though the era=
se
> reports that it succeeded, it takes a lot longer than it should (5 seco=
nds
> instead of few hundred ms) and a subsequent blank check says it failed.
> Everything I have tried so far has not got them to reprogram.
>
> The config bit settings as shown by MPLAB (v6.60) for the original and
> reprogramming are:
>   Oscillator:           INTRC-RA6 is Port I/O
>   Wathdog Timer:        Off
>   Power Up Timer:       On
>   MCLR Select Bit:      RA5 is MCLR
>   Brown Out Detect:     Off
>   Low Voltage Program:  Disabled
>   Data EE Read Protect: Disabled
>   Flash Program Write:  Write Protection Disabled
>   CCP1 Mux:             RB2
>   Code Protect:         Enabled - All protected
>
> I have desoldered all the peripherals components in case they were caus=
ing
> the trouble. So now the only connections to the Vpp, PGC and PGD pins a=
re
> from the board's programming header, but the reprogramming still fails.
>
> I've buzzed through and checked for shorts but no problems found.
>
> I have tried selecting power from the ICD2 and also power from the boar=
d -
> no luck erasing/reprogramming either way.
>
> Checking the signals on a scope: Vdd is 5V (if powered from the ICD2) o=
r
> 3.3V (if powered from the board); During programming Vpp reaches 13.5V
(rise
> time of 70ns approx); PGC and PGD both produce good squarewaves between=
 0V
> and Vdd.
>
> I've tried a couple of other ideas I've come across - adding a pull-dow=
n
of
> 1k to the Vpp line, and also a pull-up of 1k to the same line (on a
> different occassion) but with no success.
>
> Could anyone please offer any suggestions as to how to get these
> PIC16LF819's to erase and reprogram? BTW - the codespace is totally ful=
l,
> otherwise I guess I could include a bootloader to get around this. Also=
,
if
> another programmer is likely to work better for this than the ICD2 then
I'm
> willing to get one.
>
> Very many thanks,
>
> James
>
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