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Author Topic: M3.8.3 Reversing  (Read 3599 times)
pc1010
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« on: October 24, 2020, 03:26:07 AM »

Hello there Smiley
I'm trying to disassemble the old M3.8.3 ECU for educational purposes but there is one thing that is stopping me.
I don't have much idea how the external memory has to be mapped to fit in the addressing space.
As the Intel CPU inside has 16bit addressing space it can only fit 64k of data but the external ROM has 256k.
I can imagine it probably maps 8/16/32kb sectors and switches them when needed on the fly, but how that could be implemented in IDA?
Thanks for any help!  Grin
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ZpiXDK
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« Reply #1 on: July 13, 2021, 01:17:58 PM »

Any progress on this?

Iam trying to do the same thing, but Iam all new to disassembling.

In the "8XC196Kx, Jx, CA USER’S MANUAL"
- Page 350 "CHAPTER 15 INTERFACING WITH EXTERNAL MEMORY"

"The device can interface with a variety of external memory devices. It supports either a fixed 8-
bit bus width, a fixed 16-bit bus width, or a dynamic 8-bit/16-bit bus width"

Did you look at page 71?
- Table 4-1. Memory Map

"After a reset, the device fetches its first instruction from 2080H"

2080-5FFF - Program memory (internal nonvolatile or external memory)

6000-FFFF - External device (memory or I/O) connected to address/data bus (Map area is 6900-B406 in the 06A906018R, 6000-6900 is FF)

See the table for more info

My problem is were to go from here? (I have a long way for sure!)
Never used IDA before so also need to understand how that works (looking at alot of guides)
This has nothing to do with just finding some maps and altering them in winols! Cheesy (And I know it's a waste of time to disassemble this old ECU, but I want to learn!)
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You want some tuning with that pop and bang?
-Nahh it’s not good for the engine
ecuprog7
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« Reply #2 on: June 02, 2023, 04:16:41 AM »

Hi, found something for the old MCS196 family, maybe it´s useful!
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