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'[PIC:] Can't reprogram 16LF819 in-circuit'
2004\09\23@060710 by James Alston

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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 fail at
the first of the programming cycle, the Part Erase. Even though the erase
reports that it succeeded, it takes a lot longer than it should (5 seconds
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 causing
the trouble. So now the only connections to the Vpp, PGC and PGD pins are
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 board -
no luck erasing/reprogramming either way.

Checking the signals on a scope: Vdd is 5V (if powered from the ICD2) or
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-down 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 full,
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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2004\09\23@074354 by Mike Harrison

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On Thu, 23 Sep 2004 11:07:38 +0100, you wrote:

{Quote hidden}

I'm not sure it applies to this part, but I know the 12F parts are sensitive to Vcc risetime, which
can cause problems when there is capacitance or other loading on the supply.  

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2004\09\23@082423 by Anand Dhuru

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>
> I'm not sure it applies to this part, but I know the 12F parts are
sensitive to Vcc risetime, which
> can cause problems when there is capacitance or other loading on the
supply.
>

I've noticed this, the hard way. With my home made EPIC compatible, I have
no problems doing ICSP on 16FXXXs, but loads of them with 12F parts. Is
there a cure to this besides using *very* short ICSP cables?

Regards,

Anand

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2004\09\23@103029 by Mike Harrison

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On Thu, 23 Sep 2004 17:54:27 +0530, you wrote:

>>
>> I'm not sure it applies to this part, but I know the 12F parts are
>sensitive to Vcc risetime, which
>> can cause problems when there is capacitance or other loading on the
>supply.
>>
>
>I've noticed this, the hard way. With my home made EPIC compatible, I have
>no problems doing ICSP on 16FXXXs, but loads of them with 12F parts. Is
>there a cure to this besides using *very* short ICSP cables?

Use a moderately chunky MOSFET to drive Vcc, so it can get it to the right level quickly.
Here's the circuit I use to do in-system programming of 12fxxx parts on Picstart :
http://www.electricstuff.co.uk/picstart_isp.pdf

This works happily with 10uf capacitance across Vdd


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2004\09\23@105121 by John J. McDonough

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----- Original Message -----
From: "James Alston" <spam_OUTjamesaTakeThisOuTspamjpacsoft.com>
Subject: [PIC:] Can't reprogram 16LF819 in-circuit


> I have desoldered all the peripherals components in case they were causing
> the trouble. So now the only connections to the Vpp, PGC and PGD pins are
> from the board's programming header, but the reprogramming still fails.

Is PGM (pin 9) still pulled low?

> Checking the signals on a scope: Vdd is 5V (if powered from the ICD2) or
> 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.

Does Vpp start well below 1 volt?

--McD



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2004\09\23@113319 by James A

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>
> I'm not sure it applies to this part, but I know the 12F parts
> are sensitive to Vcc risetime, which
> can cause problems when there is capacitance or other loading on
> the supply.
>

Thank you for the tip Mike. I've checked this with power from the ICD2 - It
takes 15us for the Vcc pin to reach 2V, and a further 80us to reach 4.5V.

When I use power from the board instead, the waveform of the rise of Vcc is
much more drawn out - Vcc takes 1ms to reach 1.4V, then climbs quicker to
2.6V in a further 40us, and then slowly again to 3.3V (full voltage in this
configuration) in a further 2.5ms. Maybe this is due to characteristics of
the bench power supply.

Could these kind of risetimes for Vcc be significant with the
erasing/reprogramming problems? Whichever source of power the trouble is the
same.

Thanks,
James

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2004\09\23@123408 by James A

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> > I have desoldered all the peripherals components in case they
> were causing
> > the trouble. So now the only connections to the Vpp, PGC and
> PGD pins are
> > from the board's programming header, but the reprogramming still fails.
>
>  Is PGM (pin 9) still pulled low?

PGM has been floating each time I've programmed and reprogrammed. It is used
to drive a LED via an IDC header pin, disconnected during programming. I
tried it just now tied to ground via 56R but still no success.

Is the level of PGM significant? (the LVP config bit is cleared to disable
low-voltage programming)

> > Checking the signals on a scope: Vdd is 5V (if powered from the ICD2) or
> > 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.
>
> Does Vpp start well below 1 volt?

Vpp starts at 16mV.

Thanks for your assistance, John.

>
> --McD
>

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2004\09\23@125924 by Chris Emerson

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On Thu, Sep 23, 2004 at 05:34:39PM +0100, James A wrote:
> Is the level of PGM significant? (the LVP config bit is cleared to disable
> low-voltage programming)

When you erase the fuses during reprogramming, the LVP bit is
(temporarily) set, which may or may not cause problems.  Better safe
than sorry, I'd say!

Chris
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2004\09\23@131324 by Dennis Crawley

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

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

I think this is the last on 818/9

Regards,
Dennis Crawley

{Original Message removed}

2004\09\23@134851 by Dennis Crawley

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----- Original Message -----
From: "James Alston"
Sent: Thursday, September 23, 2004 7:07 AM
Subject: [PIC:] Can't reprogram 16LF819 in-circuit

Sorry, stand corrected,...
http://ww1.microchip.com/downloads/en/DeviceDoc/80159D.pdf

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2004\09\23@155218 by Mike Harrison

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On Thu, 23 Sep 2004 16:33:47 +0100, you wrote:

>>
>> I'm not sure it applies to this part, but I know the 12F parts
>> are sensitive to Vcc risetime, which
>> can cause problems when there is capacitance or other loading on
>> the supply.
>>
>
>Thank you for the tip Mike. I've checked this with power from the ICD2 - It
>takes 15us for the Vcc pin to reach 2V, and a further 80us to reach 4.5V.
>
>When I use power from the board instead, the waveform of the rise of Vcc is
>much more drawn out - Vcc takes 1ms to reach 1.4V, then climbs quicker to
>2.6V in a further 40us, and then slowly again to 3.3V (full voltage in this
>configuration) in a further 2.5ms. Maybe this is due to characteristics of
>the bench power supply.
>
>Could these kind of risetimes for Vcc be significant with the
>erasing/reprogramming problems? Whichever source of power the trouble is the
>same.

When I was looking at the 12f's, ISTR the main problem was that Picstart was not leaving enough
delay between Vcc and Vpp - it was not so much the risetime as the delay - potentially tweakable in
software, if you can get at the software....

For a producton programming jig I did a while ago I used the PP06 programmer software which comes
with source code - I didn't get as far as looking at this as I had to build the hardware anyway so
made it suitable beefy - I just wanted to get the programming time down to a minimum.

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2004\09\24@044735 by James A

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{Quote hidden}

With Vcc and Vpp initially at 0V, selecting power from the ICD2 causes Vcc
to rise to 4.5V. 22ms later, Vpp rises to 13.5V and then returns to 0V after
6ms. From that point, Vcc stays at 4.5V and Vpp remains at 0V until
programming is selected by the user. Vpp rises to 13.5V, but Vcc does not
vary at all when programming is selected. Does this sound like valid
behaviour?

>
> For a producton programming jig I did a while ago I used the PP06
> programmer software which comes
> with source code - I didn't get as far as looking at this as I
> had to build the hardware anyway so
> made it suitable beefy - I just wanted to get the programming
> time down to a minimum.
>

Many thanks,
James

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2004\09\24@045326 by James A

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> -----Original Message-----
> From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu]On Behalf
> Of Chris Emerson
> Sent: 23 September 2004 17:59
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC:] Can't reprogram 16LF819 in-circuit
>
>
> On Thu, Sep 23, 2004 at 05:34:39PM +0100, James A wrote:
> > Is the level of PGM significant? (the LVP config bit is cleared
> to disable
> > low-voltage programming)
>
> When you erase the fuses during reprogramming, the LVP bit is
> (temporarily) set, which may or may not cause problems.  Better safe
> than sorry, I'd say!
>
> Chris

Thanks Chris - I will add a resistor to the next lot.

James

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2004\09\24@045329 by James A

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> -----Original Message-----
> From: piclist-bouncesspamspam_OUTmit.edu [@spam@piclist-bouncesKILLspamspammit.edu]On Behalf
> Of Dennis Crawley
> Sent: 23 September 2004 18:44
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC:] Can't reprogram 16LF819 in-circuit
>
>
> ----- Original Message -----
> From: "James Alston"
> Sent: Thursday, September 23, 2004 7:07 AM
> Subject: [PIC:] Can't reprogram 16LF819 in-circuit
>
> Sorry, stand corrected,...
> http://ww1.microchip.com/downloads/en/DeviceDoc/80159D.pdf
>

Thanks for that - yes, I've read it before and I still can't see anything
that would affect it. It mentions ICSP wrt the oscillator pins but I'm using
the internal oscillator.

James

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2004\09\24@164233 by Peter L. Peres

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On Thu, 23 Sep 2004, Anand Dhuru wrote:

>>
>> I'm not sure it applies to this part, but I know the 12F parts are
> sensitive to Vcc risetime, which
>> can cause problems when there is capacitance or other loading on the
> supply.
>>
>
> I've noticed this, the hard way. With my home made EPIC compatible, I have
> no problems doing ICSP on 16FXXXs, but loads of them with 12F parts. Is
> there a cure to this besides using *very* short ICSP cables?

Normally the programmer software 'knows' to rise MCLR before VDD on
certain parts (like 12Fs and all other internal RC capable types I think).
I am not familiar with EPIC hardware.

Peter
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2004\09\25@034226 by James A
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{Quote hidden}

I'm just come across this page:
http://osaka.cool.ne.jp/feng3/en/vddctrl.html
It talks about problems reprogramming 12F and the 16F819 that I'm having
trouble with, and the need to raise Vpp before Vdd. Only that in his case he
had set MCLR as an I/O pin, whereas in my case it is set to be MCLR, so the
extra circuitry should not be necessary for me should it?

Thanks,
James

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2004\09\25@103256 by Peter L. Peres

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On Sat, 25 Sep 2004, James A wrote:

{Quote hidden}

I think that there is no easy solution for you. Maybe use a switch and set
it according to the pic you use.

Peter
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2004\09\25@141231 by James A

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{Quote hidden}

Thanks Peter. Just wondering if there are any 3rd-party programmers, that
might be up to the job of controlling Vdd and Vpp as required? Mike
mentioned the PP06 programmer s/w and I notice the PP06 website has a dual
PIC Programmer that could be just what I need if it works ok with my board.

James

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2004\09\25@152420 by Richard E. Teague

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>... Just wondering if there are any 3rd-party programmers, that might
>be up to the job of controlling Vdd and Vpp as required? ...


>James


http://members.aol.com/dl4yhf/winpicpr.html


here is a software package that I use with a Tait style programmer on the
parallel port. I have never used it with an F819 but it does support raising
Vdd 50 us before Vpp, and it was very recently updated, and the F819 is in
the devices list now.


Here is a link to the schematic of the parallel port programmer that I use
with this software.

http://members.cox.net/k5btp/files/sch.gif


It is available for sale at:
http://www.sparkfun.com/shop/index.php?shop=1&cart=100206&cat=3&

Just scroll down the page to: Parallel Programmer with ICSP It's not too
expensive ($22.95 USD). Or, it shouldn't take too long to put one together
from the schematic. That's what I did.



Hope this helps.

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2004\09\26@051741 by James A

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{Quote hidden}

Many thanks Richard!

James

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