1228331 ECU Processor (P4 processor info)

[Malcolm Robb, LC 0112G]

Don't want to be a pain, but my ECU would appear to have RAM from 
0x0000-0x02FF. Many parts of the code use variable storage in the 0x03XX 
area of memory. Also, one of the first instructions after reset is "lds 
 #$02FF", which I think means load stack pointer = 0x02FF, so I'm assuming 
the stack works down from there. I have no way of knowing how much of this 
RAM is battery backed up, perhaps only the first 256 or 512 bytes.  There 
are no references to anything from 0x0300-0x2FFF, although when I dumped 
this area of memory I got images of 0x0000-0x03FF in parts of it. (GM 
saving money by incomplete address decoding ?)

The code makes reference to some hardware? in the 0x3000- 0x30FF area. The 
values in these locations get transmitted as part of the ALDL data stream. 
And like Peter, the code writes to hardware? in the 0x3FF0-0x3FFF area as 
well.

The registers in the 0x4000-0x400C area seem to tie up correctly.

If anybody is interested, I can EMAIL them the contents of my ECU's memory 
map from 0x0000-0x7FFF. The EPROM (0x8000-0xFFFF) is allready on the ftp 
incomming site.

Thanks for the help so far
Malcolm Robb, LC 0112G

-----Original Message-----
From:	steve ravet [SMTP:sravet at arm.com]
Sent:	Tuesday, April 11, 2000 10:45 PM
To:	gmecm at diy-efi.org
Subject:	Re: 1228331 ECU Processor (P4 processor info)



Peter Gargano wrote:
>
> According to the disassembly of BUA, here are some other locations
> that Steve has not mentioned at:

They're on there now.  Do you have any more info about the region 
3cf0-3fff?  I'd like to fill it in a little more.  Does the HUD code really 
fit from 5800-58ff?
* steve

>
>   http://www.diy-efi.org/gmecm/ecm_info/p4_registers.html
>
> $04xx        Heads up display (HUD) RAM variables (if present)
> $3fC0-$3fff  Other hardware registers controlling peripheral devices
> $58xx        HUD code (if present)
>

--
Steve Ravet
steve.ravet at arm.com
ARM,Inc.
www.arm.com
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