ECM 1227748, creating a new ECU file?

[Nick McAlpin]

Steve/List,

I am going to figure out this ECm one way or another.  =)  It wasn't 
too many years ago that I was in college and was pretty proficient 
with 8051 (intel microcontroller) assembler.  While the motorola 
stuff is quite different, i've already ran the BIN through a 
disassembler and am working on an LST file for it now.  I was 
elated when I recognized the first subroutine (the checksum 
routine).  I couldn't quite figure out why you would loop through the 
code adding all the byte values together, ignoring overflows and 
everything else, until it finally dawned on me!

It's slow going since it has been a few years since i've worked in 
any assembly (not to mention learning the motorola way of doing 
things) but i'm confident with a little list help i should be able to 
figure the code out and in turn identify some of the obscure 
variables that could be changed/set up in the ECU for playing.

As you mentioned, there are a couple of very obvious tables.  i am 
working on the ECU file in tandem with the LST file, and the LST 
will shed more information on what exactly I need to identifiy in the 
BIn for the ECU.

On 20 Feb 2001, at 14:05, steve ravet wrote:

Date sent:      	Tue, 20 Feb 2001 14:05:52 -0600
From:           	steve ravet <sravet at arm.com>
To:             	gmecm at diy-efi.org
Subject:        	Re: ECM 1227748, creating a new ECU file?
Send reply to:  	gmecm at diy-efi.org

> Nick, I have the same ECM and am hoping to put it on a boat some day.  I
> have looked through a few bin files and there are 7 or 8 or so 3d tables
> that jump right out at you.  That's the extent of my work, though, I
> don't know what the tables do.  Tunercat doesn't seem to support 1227748
> although he might be talked into it.  I doubt Terry K has an editor
> either, just because it's not that common an ECM.  but who knows, as
> him.  I'd be interested in swapping info on this ECM if you come up with
> anything.
> 
> Nick McAlpin wrote:
> > 
> > What does it take to make a new ECU file from scratch?
> > 
> > I'm the one with an 88 coupe who got some help from the list over
> > the past few days (thanks all!) and i am interested in working with
> > the EPROM code/tables a little bit but being a less common ECM,
> > the ECU doesn't seem to exist.
> > 
> > So, my question, is building an ECU really not much more than
> > looking through the bits of the .BIN, identifying tables purely by
> > pattern and then playing with them to find out what they do?  what
> > about single byte memory spots - do you guys just change the
> > value one byte at a time to find out what it does?
> 
> Basically.  Once you find the tables, you can start changing values
> (like zero out an entire line) and see what the effect is on timing or
> fuel.  You don't want to do that on a car, you want to do it on an ECM
> testbench.  There is some information about building an ECM testbench on
> the WWW page http://diy-efi.org/gmecm/projects/ecm_testbench/
> 
> There is some info in the archives, mostly from Ludis, about this ECM. 
> Search around in there also.
> 
> > 
> > is there any standardization in the table formats of ECM's?  For ex.
> > if I find a table of size X columns and Y rows that it is probably
> > table Z?  or is every ECM/bin different.
> 
> As I understand it, bins that share the same mask code have tables in
> the same places, and the same sizes, as each other.
> 
> > 
> > It seems like if I have to start from total scratch, I could end up
> > burning 1000's of EPROMS and doing a lot of guesswork (and hope
> > not to break anything in the meantime?)
> 
> Yes to the 1000's (unless you get an emulator), no to the breaking stuff
> if you use an ecm testbench.
> 
> --steve
> 
> -- 
> Steve Ravet
> steve.ravet at arm.com
> ARM,Inc.
> www.arm.com
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