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'[PIC] ICSP question'
2005\11\10@204932 by scott larson

picon face
when programming the 16F876 using ICSP, should the RB3/PGM low voltage
programming pin be grouned?
i have programmed 3 of these chips, and forgot to ground this pin, and it
appears that when i make it an output, it doesn't seem to work.
have i permanently damaged the RB3 pin?

--
Scott Larson
3201 S. State. St. box 2561
Chicago, Il, 60616
619-400-9775
http://goldscott.com

2005\11\10@211550 by Sergey Dryga

face picon face
scott larson <goldscott <at> gmail.com> writes:

>
> when programming the 16F876 using ICSP, should the RB3/PGM low voltage
> programming pin be grouned?
> i have programmed 3 of these chips, and forgot to ground this pin, and it
> appears that when i make it an output, it doesn't seem to work.
>  have i permanently damaged the RB3 pin?
>
> --
> Scott Larson
> 3201 S. State. St. box 2561
> Chicago, Il, 60616
> 619-400-9775
> http://goldscott.com


Scott,
If you are programming at high voltage (traditional mehtod), RB3 has no
effect, it can be left floating.  Make sure to select high-voltage programming
in config, this might be causing RB3 problem.
In CCS PCW use:
#FUSES NOLVP

Sergey Dryga
http://beaglerobotics.com

2005\11\10@221022 by Maarten Hofman

face picon face
> when programming the 16F876 using ICSP, should the RB3/PGM low voltage
> programming pin be grouned?
> i have programmed 3 of these chips, and forgot to ground this pin, and it
> appears that when i make it an output, it doesn't seem to work.
>  have i permanently damaged the RB3 pin?

I have frequently programmed the 16F877 (which has the same datasheet,
I believe) using ICSP while leaving RB3 floating, and have had no
problems with this configuration. I did make sure LVP is off in the
configuration, though.

Greetings,
Maarten Hofman.

2005\11\10@222800 by scott larson

picon face
ahh, yes, the default option on my programmer is LVP ON.
after turning it off, everything works fine.
thank you very much.

On 11/10/05, Maarten Hofman <spam_OUTcashimorTakeThisOuTspamgmail.com> wrote:
{Quote hidden}

>

2005\11\11@023149 by Wouter van Ooijen

face picon face
> when programming the 16F876 using ICSP, should the RB3/PGM low voltage
> programming pin be grouned?

For LVP is should obviously be high. For HVP some chips / date codes /
phases of the mooon seem to require that it is held low. In both cases
you can use a resistor to avoid problems.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\11@023149 by Wouter van Ooijen

face picon face
> I have frequently programmed the 16F877 (which has the same datasheet,
> I believe) using ICSP while leaving RB3 floating, and have had no
> problems with this configuration. I did make sure LVP is off in the
> configuration, though.

I have frequently cossed the street without looking left and right. I am
still alive, so it must be perfectly safe.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\11@055122 by Rob Hamerling

flavicon
face


Maarten Hofman wrote:

> I have frequently programmed the 16F877 (which has the same datasheet,
> I believe) using ICSP while leaving RB3 floating, and have had no
> problems with this configuration. I did make sure LVP is off in the
> configuration, though.

If you mean in the hexfile your want to transfer to the PIC: I would
think this is irrelevant.  To me it seems sensible only when the LVP was
already cleared in the target config bits _before_ transferrring the hex
file.

Regards, Rob.

--
Rob Hamerling, Vianen, NL phone +31-347-322822
homepage: http://www.robh.nl/

2005\11\11@070604 by Vasile Surducan

face picon face
On 11/12/05, Wouter van Ooijen <.....wouterKILLspamspam@spam@voti.nl> wrote:
> > I have frequently programmed the 16F877 (which has the same datasheet,
> > I believe) using ICSP while leaving RB3 floating, and have had no
> > problems with this configuration. I did make sure LVP is off in the
> > configuration, though.
>
> I have frequently cossed the street without looking left and right. I am
> still alive, so it must be perfectly safe.

 Because you're not living in the US. Then crossing the street must
be precedeed by looking to the left, to the right and up.

cheers,
Vasile

2005\11\11@072301 by Wouter van Ooijen

face picon face
> If you mean in the hexfile your want to transfer to the PIC: I would
> think this is irrelevant.  To me it seems sensible only when
> the LVP was already cleared in the target config bits _before_
> transferrring the hex file.

I have seen troubles with at least some PIC type/revision, I think with
an early F877, even when the .hex states HVP and the PIC is configured
for HVP. My guess is that is has to do with the fact that erasing the
chip sets the config to LVP. Note that a fresh (blank) chip is
configured for LVP.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\11@073210 by olin piclist

face picon face
scott larson wrote:
> when programming the 16F876 using ICSP, should the RB3/PGM low voltage
> programming pin be grouned?

You're not supposed to have to, and I think you can actually get away with
it on that chip.  It's still a good idea though.

> i have programmed 3 of these chips, and forgot to ground this pin, and
> it appears that when i make it an output, it doesn't seem to work.
>  have i permanently damaged the RB3 pin?

By leaving it floating during programming?  Very unlikely.  There is
probably something else going on.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\11\11@085537 by Maarten Hofman

face picon face
> > I have frequently programmed the 16F877 (which has the same datasheet,
> > I believe) using ICSP while leaving RB3 floating, and have had no
> > problems with this configuration. I did make sure LVP is off in the
> > configuration, though.
>
> I have frequently cossed the street without looking left and right. I am
> still alive, so it must be perfectly safe.

It is funny how you added the "so it must be perfectly safe" which I
did not write (nor meant to imply). I merely wrote what I experienced
so far. If I intended any implication, it was that the 16F877 did not
get damaged in any way. This might not be a "perfect" statement, but
from my knowledge of microcontroller design, it seems highly unlikely
it would.

Greetings,
Maarten Hofman.

2005\11\11@093827 by Wouter van Ooijen

face picon face
> It is funny how you added the "so it must be perfectly safe" which I
> did not write (nor meant to imply). I merely wrote what I experienced
> so far. If I intended any implication, it was that the 16F877 did not
> get damaged in any way. This might not be a "perfect" statement, but
> from my knowledge of microcontroller design, it seems highly unlikely
> it would.

Maybe I 'overreacted' a little, but the point is that observations where
a safety measure (tying LVP low) were necesarry should take precedence
over observations where it was not necessary. Ufortunatley the latter
are often more numerous, so they get mentioned more often. This applies
to LVP pull-down, but also to using TTL levels for RS-232 interfacing,
omitting decoupler capacitors, direct bit-manipulation of port
registers, etc etc.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\11@110323 by olin piclist

face picon face
Wouter van Ooijen wrote:
> I have seen troubles with at least some PIC type/revision, I think with
> an early F877, even when the .hex states HVP and the PIC is configured
> for HVP. My guess is that is has to do with the fact that erasing the
> chip sets the config to LVP. Note that a fresh (blank) chip is
> configured for LVP.

I agree with Wouter.  I've also seen problems doing HVP with the PGM pin
floating, even though it's not supposed to matter according to the
documentation.  I sortof remember I bumped into this on a 16F628 a few years
ago.  I'm pretty sure Jim Robertson also reported something like this.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\11\11@185048 by Bob Axtell

face picon face
Olin Lathrop wrote:

> Wouter van Ooijen wrote:
>
>> I have seen troubles with at least some PIC type/revision, I think with
>> an early F877, even when the .hex states HVP and the PIC is configured
>> for HVP. My guess is that is has to do with the fact that erasing the
>> chip sets the config to LVP. Note that a fresh (blank) chip is
>> configured for LVP.
>
>
> I agree with Wouter.  I've also seen problems doing HVP with the PGM pin
> floating, even though it's not supposed to matter according to the
> documentation.  I sortof remember I bumped into this on a 16F628 a few
> years
> ago.  I'm pretty sure Jim Robertson also reported something like this.
>
>
> ******************************************************************
> Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
> consultant in 2004 program year.  http://www.embedinc.com/products

I am on my third design with F88 and LF88. To allow flawless, reliable
programming on my client's DIY K128 in ICSP mode, the PGM pin has
to be connected through a 10K (or smaller) resistor to GND. Driving a
base pin of a transistor through a 3.3K worked just as well. Programming
failure is ZERO.

But I had to re-arrange the first design to fix the PGM business. No
matter what MicroChip says, it is NOT reliable enough for primetime.

--Bob



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