Re: C3 with 8192 ALDL

[Shannen Durphey <shannen@grolen.com>]

I just picked up an eprom from one of these babies.  The E cars were
sometimes equipped with an in dash CRT.  The screen I've got looks
like a touch screen, and it's labelled (IIRC) Diagnostic, Climate, and
Radio.  The ALDL has a special cover with a jumper molded in it.  The
jumper grounds the diagnostic line at all times, and the same jumper
is installed in E cars without the CRT.  I remember that the service
manuals say the BCM will lose communications from the ECM if the ALDL
cover is not installed.  Does it seem likely that the 8192 is for
communication with the bcm and other systems?
Shannen




Ludis Langens wrote:
> 
> I believe I've found a C3 ECM which supports 8192 baud ALDL.  The ECM in
> question is the 1227057.  It was used only in E-bodies with the 3.8 SFI
> V6.  In 1986 the engine RPO was LG2, and in '87 it was LG3.
> 
> While collecting data for my trivia message, I opened up a '7057
> thinking it was a '7148 (the markings had been scratched off).  The
> internal circuit boards are similar, but not quite.  The '7057 uses P4
> style quad driver chips instead of the older DIP package style of the
> '7148.  The '7057 has an extra screw in it's case to hold the quad
> driver's heat sink.
> 
> The other big difference is in the 40 pin DIPs.  A '7148 contains a
> 26369, 23263, 51179, 51174, and a 21633.  The first two are timer chips,
> the second two mask ROMs, and the last is the CPU.  The '7057 contains a
> 26369, 23263, 24007 aka CE1205, 44006 aka CE1204, and a 35997.  I assume
> the third and fourth are the mask ROMs and the last is a different CPU.
> 
> I disassembled the software code in the '7057's MEMPAK.  It turns out
> that this ECM uses a Hitachi 6303 (or 6301) MPU instead of the normal
> GM-custom CPU used in so many C3 ECMs.  I had to change my disassembler
> to handle the extra incompatible opcodes of the 6303.
> 
> I found the ALDL tables in the '7057's EPROM.  There are multiple tables
> stored in the linked list format common to many early P4 ECMs!  Thus,
> this ECM may use 8192 baud ALDL.  The 6303 contains the necessary UART.
> 
> I don't know how common the '7057 is.  It's only in two years worth of
> E-bodies, which I don't recognize on sight.  It is possible that I've
> walked past many of them.  The engine looks just like any other Buick
> 3.8.
> 
> --
> Ludis Langens                               ludis (at) cruzers (dot) com
> Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
> 
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