Update on 93 Z28 disassembly

[Roger Heflin]

On Mon, 14 Dec 1998, Mike wrote:

> >
> >I have had some help from several people, thanks everyone.   I am
> >going to be updating my web page later tonight (probably late), but
> >here is what I have found so far.   I am mostly (with some help)
> >decoded the ALDL commands.  My car seems to accept (first bytes) of 
> >0xF4, 0x42, 0x40, 0x01, 0x02.   WIth the 0x04 it has several modes
> >0x00, 0x01 (basic data out), 0x02, 0x03, 0x04, 0x0a (clear codes).  I
> 
> You mean "With the 0xF4..." right?

Yes, that is correct.  I did mean 0xF4.


Also for all of the other modes it looks (other than the 0xF4 modes),
like the ecm just saves the input data into a certain memory location.
I will have to determine if it does something with the input at a
later time.

 > 
> >have notes on what is in the 0x01 and 0x0a mode, the others are a
> >mystery right now.   I have found the data stream for the 0xF4 0x01
> >data mode, and I have documentation on what data is contained in that
> >mode.   The data it has lines up what what I already determined (at
> >the few points I had already determined).  The error for bad prom (two
> >different bits) are both setting the bit that should be set in the
> >data stream for a bad prom.   Everything that should be accessing a
> >A/D port, is, so I know what most of the A/D registers are connected
> >to.   I should be able to find out what alot of the code is doing
> >since with this info I know what most (or at least 1 or 2 ) of the
> >inputs to any formula should b.
> 
> It's interesting that this ECM uses an HC11 whose base register set seems
> largely intact (compared to "standard" HC11s). Different than any other GM
> ECM I've seen, though that number is comparatively limited.
> 

Keep in mine, I am using a 68HC11F1 as the model, so far though, when
I have looked at an interrupt, it has been manipulating registers that
you would expect to be manipulated for the given interrupt.  I am
going to keep my eye out for any inconsistancies with the F1 variant
and what the code does.


> >Here is a question:  I have identified that two of the modes output
> >data streams similar to the 0x01 mode (different data, and fewer
> >bytes), diacom does not read these data streams at all.  One of the
> >data streams has 15 bytes, and the other I believe has 3 bytes.  I
> >know from the service manual that there should be info on the ABS
> >subsystem and maybe other subsystems available.   Does anyone know
> >if all the extra data streams go the same ALDL connector?
> >
> 
> On these cars (and others with bidirectional ALDL links) the ALDL data is a
> shared, one-wire bus between the ECM, the ALDL connector and various other
> modules. These can include the CCM (Central Computer Module), the instrument
> cluster, climate control, ABS etc. Sometimes some or all of these
> peripherals are connected, sometimes none...depends on the option level of
> the car.
> 
> ALDL diagnostic connector messages, if memory serves, use the F4 identifier.
> Other identifiers are reserved for the other modules on the bus. Each
> identifier might represent a request from a different device on the bus.
> Diacom will only make use of the F4 messages and modes.
> 
>

I checked my service manual, and it does document some of the stuff
the abs returns.  I am going to have to carefull look at the extra
codes and see what is what.

> -----
>  Mike
> 
> 
					Roger