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'[PIC]12f675 osccal'
2006\01\18@071250 by Dennis Crawley

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Hi,
The original calibration value of a 12f675 is seems to be erased.
The original value it was read it with MPLAB and PS+, and it was "retlw
0x48" at 3fff.
I wonder if it is possible to re-write this value.

The pic was also missconected "once" on the protoboard: Vdd to pin 2 and gnd
to pin 7 (shifted one hole), It was reprogrammed and that pins work nice...

The main problem now is when the ps+ finish to verify, there are a lot of
bad memory locations compared with the program. If it done twice, the pic is
succesfully programmed... and this never happened before, as long as i
recall.

No icsp is used.

Any comments about trust on "that" pic or about how to reprogram the osccal
is
apreciated.

Dennis Crawley
Argentina

ps: no generalisimos arround,... but is wost.




2006\01\18@072359 by Bob Axtell

face picon face
Just set an org at 03fff, and install the instruction.
Try it in MPLAB, compile it, then look at the PGM
array. It will be right there.

--Bob


Dennis Crawley wrote:

{Quote hidden}

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2006\01\18@075351 by Jan-Erik Soderholm

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Bob Axtell wrote :

>
> Just set an org at 03fff, and install the instruction.
> Try it in MPLAB, compile it, then look at the PGM
> array. It will be right there.
>
> --Bob

Maybe check how the programmer handles this.
I guess that any programmer that knows what it's
doing, would first read the value from h'3FFF' and then
add that to the code from the HEX file (so it will be
written back).

Check that the programmer realy uses the value from
HEX file (if any) instead of the read value (that we know
is wrong) from the chip itself.

Also remember to comment out the ORG and RETLW
from the source, or you'll end up with wrong cal values
if you use another 12F675 then the one you're using
right now...

Jan-Erik.



2006\01\18@080823 by olin piclist

face picon face
Dennis Crawley wrote:
> The original calibration value of a 12f675 is seems to be erased.
> ...
> The pic was also missconected "once" on the protoboard: Vdd to pin 2
> and gnd to pin 7 (shifted one hole),
> ...
> The main problem now is when the ps+ finish to verify, there are a lot
> of bad memory locations compared with the program.
> ...
> Any comments about trust on "that" pic

How many $10 have you already spent wondering whether it makes sense tossing
out a suspect $1 part?  How many $100 will it cost if you don't and you were
wrong?  *Think* about it.


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

2006\01\18@081534 by Alan B. Pearce
face picon face
>Any comments about trust on "that" pic or about how to
>reprogram the osccal is apreciated.

Well others have said how to reprogram the value, but no-one mentioned
anything about what happened to the rest of the chip.

What you say about the now unreliable programming suggests that the 13V that
is applied to go into programming mode appeared on the incorrect chip pin
when it was mis-socketed, and this has damaged the chip, to a a point where
I would suggest its reliability is now quite suspect. It will have had ad
least 7V between Vcc and Gnd, and possibly 12-13V depending on just which
direction the pinout was wrong when in the socket.

I would recommend tossing that one (use it in a kids toy if you really
mustn't toss it) and getting another for serious use.

2006\01\18@090756 by Dennis Crawley

picon face
Bob Axtell <.....engineerKILLspamspam@spam@cotse.net> wrote:
> Just set an org at 03fff, and install the instruction.
> Try it in MPLAB, compile it, then look at the PGM
> array. It will be right there.
>
> --Bob

Well, the pic may be locked. I've made
  org 0x3fff
  retlw 0x48
but when the pic is read it, it return a nop at that address.

I don't know if the programmer settings is related to, because the range is
set at start addres 0, end address 3fe, and it can't be modified to 3ff. In
the same window, the calibration memory check-box is on.

I asume the pic some how fail to write at 3fff. I will try to program it,
but with a 12F683 device stting, with the same program, and see what this
does.

Dennis


2006\01\18@091829 by Jan-Erik Soderholm

face picon face
Dennis Crawley wrote :

> I don't know if the programmer settings is related to,
> because the range is set at start addres 0, end address 3fe,
>  and it can't be modified to 3ff.

So the programmer expects that the PIC already has a valid
cal-value in 3FF, and does not accept another value from the
HEX file. Seems as a logical deafult setting...

> In the same window, the calibration memory check-box is on.

And what if you de-check it ?

> I asume the pic some how fail to write at 3fff. I will try to
> program it, but with a 12F683 device stting, with the same
> program, and see what this does.

But it must be possibole to tell the programer that the cal-
value is "lost" and that it should program a new value from
the HEX file. Or can it be specified as a command line option ?

Jan-Erik.



2006\01\18@093904 by Dennis Crawley

picon face
> How many $10 have you already spent wondering whether it makes sense
> tossing out a suspect $1 part?
> How many $100 will it cost if you
> don't and you were wrong?  *Think* about it.

Ok.



2006\01\18@094607 by Mark Rages

face picon face
On 1/18/06, Dennis Crawley <dennis.crawleyspamKILLspamusa.net> wrote:
{Quote hidden}

The PICkit has a button (in the host software) to recalibrate your 12F675.

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.
 - fortune cookie

2006\01\18@101246 by Dennis Crawley

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Jan-Erik Soderholm <.....jan-erik.soderholmKILLspamspam.....telia.com> wrote:
> Dennis Crawley wrote :
> But it must be possibole to tell the programer that the cal-
> value is "lost" and that it should program a new value from
> the HEX file. Or can it be specified as a command line option ?
> Jan-Erik.

Jan-Erik,
I did it, cheating the MPLAB-ps+ with a 12f683 type, with the code that Bob
told me to do it. Now the value is in the right place. Analyzing what I did,
I forgot to change the pic type the first time I programmed it this morning.
I think this is the explanation. Since I won't use this particular pic any
more, elucidated by "my own" common sense, confirmed by my soul guru Olin
:), I'll repeat what I did this morning, expecting a nop at 3fff, So to be
sure.

Thank a lot for the advices and helps, to you, extensive to Olin, Bob and
Alan.

Dennis Crawley
Argentina

ps: do what I did is not a sin, isn't it?



2006\01\18@165325 by Steph Smith

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face
I seem to remember the procedure to recalibrate osccal
was mentioned in the pdf's for the PICkit1,available in
the developement tools section of micro's homepage.
the early versions of pickit1 had a nasty habit of erasing
(i.e writing over) the osccal location.Hope this helps ; )

2006\01\18@202745 by andrew kelley

picon face
I would think that you can set a clock out and measure the frequency
with a scope and adjust oscal accordingly.

On 1/18/06, Steph Smith <EraseMEzapsmithspam_OUTspamTakeThisOuTblueyonder.co.uk> wrote:
> I seem to remember the procedure to recalibrate osccal
> was mentioned in the pdf's for the PICkit1,available in
> the developement tools section of micro's homepage.
> the early versions of pickit1 had a nasty habit of erasing
> (i.e writing over) the osccal location.Hope this helps ; )

2006\01\18@204305 by Chen Xiao Fan

face
flavicon
face

> -----Original Message-----
> From: piclist-bouncesspamspam_OUTmit.edu
> [@spam@piclist-bouncesKILLspamspammit.edu] On Behalf Of Mark Rages
>
> The PICkit has a button (in the host software) to recalibrate
> your 12F675.
>

Just want to add both PICkit 1 and PICkit 2 have this function.

Another thing is that 0x3400 is the rough value based on my
experience with 12F629 and 12F675.

Regards,
Xiaofan

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