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PICList Thread
'programming 12C671 calibration memory'
1999\04\20@095443 by John

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Hi all,
I need some illumination on programming the 12C671.  I have a program
that I can burn into a 12C671/JW EPROM without any problems (using PIC
Start Plus).  Program, configuration, ID, and calibration locations all
program without a hitch; but when I put an OTP equivalent in and burn it,
an error comes up saying the calibration memory doesn't match.  OK...
I burn another OTP without programming the calibration memory and get no
error messages; the programmed OTP (by all appearances) runs properly.

I feel like I'm whistling past the graveyard by ignoring this issue.
I've RTFM but don't understand fully the implications of programming or
not programming the Calibration memory.  (I am not using any of the chip's
A/D functions.  GP0,1,2,3 pins are all set up for digital I/O:  ADCON1
at address $9F is set to $07.)  Anybody fluent with the 12C671?

TIA,
John
______________________________________________________________________________

John Leonard, instrument technician                        Electron Hacker
College of Science & Engineering                           Bit Banger
Saginaw Valley State University                            Bassist
University Center, MI USA  48710                           Dad
_____________________________________________________________________________

1999\04\20@101111 by Quentin

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Your Oscall value is already programmed in the OTP. Pic Start tries to
program the Oscall vallue it's got in it's own memory into the 12Cxxx
but finds that the PIC's memory is not empty. It will not program it
then and gives you an error message.
As this only happens after your main program has been stored in the PIC,
it is OK to just ignore it.

BTW, I use Picstart Plus via MPlab 4. I get a message that the
callibration has already been programmed on a OTP.

Hope this helps.
Quentin

1999\04\20@114755 by Dwayne Reid

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>Hi all,
>I need some illumination on programming the 12C671.  I have a >program that
I can burn into a 12C671/JW EPROM without any problems >(using PIC Start
Plus).  Program, configuration, ID, and >calibration locations all program
without a hitch; but when I put >an OTP equivalent in and burn it, an error
comes up saying the >calibration memory doesn't match.

Standard problem with PicStart Plus.  Their 'one button program'  defaults
to programming ALL locations within the device.  This includes the
calibration location which was programmed at the factory.

Easiest solution to go to the 'Picstart Plus' menu, select 'program', then
uncheck the 'calibration value' box.  Program your devices from that menu.

You are doing no harm the other way, other than the annoyance of that
warning message.  As far as I can tell, the programmer sees that the
calibration location is already programmed and simply skips it, along with
issuing the warning message.

dwayne


Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 15 years of Engineering Innovation (1984 - 1999)

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1999\04\20@131524 by wwl

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On Tue, 20 Apr 1999 09:52:55 -0400, you wrote:

>Hi all,
>I need some illumination on programming the 12C671.  I have a program
>that I can burn into a 12C671/JW EPROM without any problems (using PIC
>Start Plus).  Program, configuration, ID, and calibration locations all
>program without a hitch; but when I put an OTP equivalent in and burn it,
>an error comes up saying the calibration memory doesn't match.  OK...
>I burn another OTP without programming the calibration memory and get no
>error messages; the programmed OTP (by all appearances) runs properly.
>
>I feel like I'm whistling past the graveyard by ignoring this issue.
>I've RTFM but don't understand fully the implications of programming or
>not programming the Calibration memory.  (I am not using any of the chip's
>A/D functions.  GP0,1,2,3 pins are all set up for digital I/O:  ADCON1
>at address $9F is set to $07.)  Anybody fluent with the 12C671?
Calibration is for the speed of the internal oscillator speed, nothing
to do with the ADC. It is factory programmed to trim the oscillator
close to 4MHz, so your programmer will complain if you tell it to
program the cal data on an OTP (and if it is dumb enough to try
programming it with anything other than FF it may corrupt the factory
value).
If you erase a JW device, you need to re-program the cal data to what
it was (for that individual chip) from the factory (you did make a
note of it & write it on the device, right?)
If you are not using the INTRC osc option you can completely ignore
it.
All this is in TFM - have another R!

1999\04\20@132408 by Lawrence Lile

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I'll take a shot at this, John.  The way I understand it, the calibration
memory in OTP parts is set at the factory, individually for each chip.  Once
you program a location in an OTP part, it is set in stone (or silicon) , so
your programmer can't change it.  If the calibration memory happens to match
the number in your program (probably defaults to 0Xff or something...) then
you won't see the error message.

Your JW part will accept new calibration memory setting, and therefore won't
run with the correct timing unless you SET the calibration memory for each
individual chip.  If you didn't write this down before you erased the chip
first time, (how many times have I forgotten to do this?) then it is gone.

Trust that the OTP calibratrion memory is programmed properly.  You can
whistle confidently past the graveyard, no ghosts will come out to haunt you
this time.


-- Lawrence Lile

{Original Message removed}


'programming 12C671 calibration memory'
1999\05\03@151613 by John Payson
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|Your JW part will accept new calibration memory setting, and therefore won't
|run with the correct timing unless you SET the calibration memory for each
|individual chip.  If you didn't write this down before you erased the chip
|first time, (how many times have I forgotten to do this?) then it is gone.

|Trust that the OTP calibratrion memory is programmed properly.  You can
|whistle confidently past the graveyard, no ghosts will come out to haunt you
|this time.

On a "nice" programmer, if your code includes the proper opcode for a
calibration instruction but that location in the chip contains a different
value, the programmer will just accept the one in the chip (not try to
burn the bits that happen to be different).  If you are using such a prog-
rammer, you can just include a movlw (50x's) or retlw (67x's) at that loc-
ation and be fine whether you're using OTP or /JW parts.

Otherwise, for the '50x parts you may (if you don't care about oscillator
speed) leave the location blank and things will still work.  On the '671,
this won't work since a call to the last location will cause code execu-
tion to wrap to the first location creating and endless-loop condition.

To avoid this, you may wish to code something like [at address zero]:

       btfsc   PCLATH,0
        goto   START
       bsf     PCLATH,0
       movlw   default_cal_value_plus_one
       call    $7FF
START:
       movwf   Calib

If location $7FF is unprogrammed, this will use the default calibration
value; otherwise, it will use the one at $7FF.  Similar tricks may be used
on the '50x parts to allow for a useful default when the calibration addr-
ess isn't programmed, but care must be used with the bank-switching jumps.

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