CPU's

[Bob Wooten]

Gents,

So let me see if i have this straight.  the BCC is not in the firmware,
though the prom ID is.  the prom ID has the detailed information specific
to the application & it can lead one to the BCC.  this is providing that
you have access to this information that will get you there?  it does not
appear that this is essential if you are going to change the calibration
because once you do both the BCC & the Prom ID are no longer valid (as far
as the General is concerned).  i am following that the letter portion of
the BCC was re-used & that the number was changed to keep it different from
others.  

here is what i am not following, you said that the Mask byte (not two bits,
forgot the Basic EE from school), "might not have the same table layout". 
so, this means that there really is not a simple rule here.  i was thinking
(assuming i suppose), that this being the truth would make it rather easy
to write stuff like Win Bin & Tuner Cat for that Mask byte.  it appears
not.  

sounds to me like a simple two dimensional table (like i have) is not
allways going to tell the truth in this situation.  this sounds to me like
you have to know more about the entire application to be able to nail down
for sure what is what.  true?

so saying that one has a 7730, w/#8D, might or might not lead me to the
right tool to play with the calibration.  but if i were to say that it was
a 91 Vette, 5.7L, E-code, 7730, #8D, 5991 scan ID would get me there,
knowing that there could be more than one Prog p/n & more than one BCC,
which might or might not have the same last 4 digits.  

right?

thanks guys.
Bob


> [Original Message]
> From: Ludis Langens <ludis at cruzers.com>
> To: <gmecm at diy-efi.org>
> Date: 12/4/00 1:56:48 PM
> Subject: Re: CPU's
>
> Bob Wooten wrote:
> > 
> > the first is how do i determine the Broadcast code?
> 
> Download/build a copy of BitHoist.  It'll try to tell you the BCC.
> 
> > i have Win Bin, AFR Modifier, &
> > data master all loaded up & none of them are telling (or i am missing
it).
> 
> The BCC isn't in the chip.  The scan id is.  Knowledge of the scan id
> can usually lead to a BCC.
> 
> > SW Template:
> >         The software template, or ID Byte, is always a two bit code
that describes
> > the layout of the calibration.
> 
> Eight bit, one byte, two character, ...
> 
> > These are the exact locations of tables &
> > formulas that calculations are performed.  By looking @ the SW template
you
> > can know the locations of the tables in the calibration
> 
> Some ID bytes (aka mask bytes) are reused.  GM ran out sometime in the
> 1990's.  Also, some ID bytes have multiple versions.  For example, there
> are probably enough different 1227148 mask $31 variations that all of
> Bruce's little guys can have their own.  It isn't currently clear if the
> variations have the same table layout or not.
> 
> >         The broadcast code is a four letter group that is unique to the
actual
> > firmware in that ECM.  This is specific to the application (91 Camaro,
5.7L
> > motor, 700R4, 3.42 gears, etc) and the calibration.
> 
> The letter portion of some BCC's is reused.  It appears that the letter
> portion is enough to identify a specific application.  If there are
> updated chips for that application, they got the same letter code with a
> different number code.  Newer updates (since about 1988/89) seem to have
> a new letter code.  This might be because the update often works on a
> different set of vehicles.
> 
> > The /1563 number is
> > the last four digits of the GM part number for the calibration. (BW
> > confusion here, why is it +1 digit?)
> 
> The +1 isn't consistent.  Often the numbers are close, but they could be
> totally different too.
> 
> >         The scan ID or the Prom ID is a four digit number that is
programmed into
> > the firmware
> 
> Yet another last four digits of a GM part number.
> 
> -- 
> Ludis Langens                               ludis (at) cruzers (dot) com
> Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
> 
> 
>
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> 



--- Bob Wooten
--- r71chevy at earthlink.net
--- 71-91 Camaro


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