ALDL stream recycle time

[Dave Zug.]

Cool, thanks ludis - This one was on the back back burner and just moved up
some ;-)

The custom scan tool is an HC08 and some 7-segs on a proto board. Been in
the works for about 2 years, I have about 11 hours into it so far :-( and
had it completed for the GN stream then lost the car. I'm almost at the
point (poor excuses deleted) that I can pick it back up for the camaro.

The total plan has been to use the SCI / SPI to a PC... when I learn how to
really do it right.


----- Original Message -----
From: Ludis Langens <ludis at cruzers.com>
To: <gmecm at diy-efi.org>
Sent: Monday, October 30, 2000 12:29 AM
Subject: Re: ALDL stream recycle time


> Dave Zug wrote:
> >
> > You mean that the stream is not simply 'completely' populated and THEN
spat
> > out, that it reads each location just before spitting it?
>
> Yup.  There isn't enough RAM in the ECM to do otherwise.  Actually,
> sometime in the late '80's GM started capturing both bytes of a 16 bit
> variable before sending them out.  In older ECMs (like the '1227148),
> you can get the high byte of the "old" value and the low byte of the
> "new" value.  If the injector pulse width went from 254->258->262, it
> might look like it went 254->2->262.  This problem is fixed by capturing
> all 16 bits before sending the high byte.
>
> > Putting the good stuff in the first 10 bytes and shortening the quantity
> > transmitted to 10 would do it if I could have my way.. but the 63 thing
> > works if like you say it changes a few times during the 63 byte
transmission
> > time.
>
> Yes, it's possible to reduce the length of the 63 byte packet.  You'll
> have to have custom scan tool software to handle your shortened packet
though.
>
> --
> Ludis Langens                               ludis (at) cruzers (dot) com
> Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
>
>
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