Is it possible to extract binary/firmware from MC68331CAG20 and modify it?

[onesystem]

This chip is part of communications gateway. I have 4 of them, so there might be several possible takes.
I don't know the feasibility of the project - what I would like to do is enable baud rate on three of the communication gateway devices (physically present, dip switches, but do not respond to toggle), and on the one that does have the baud rate enabled I need to enable an option that is already enabled on the other three.

There is a ten pin port that is connected the MCU, but if other pins access needed I can solder/connect to it. So there are no limits to how I have to connect to it, it depends on anyone's experience/ability on this forum. If there is no one who played with these MCUs, then it is a dead project for me!

[srb1954]

The MC68331 series doesn't have internal ROM so there must be external program memory in the system. My guess is that it is the two 32-pin PLCC chips below the RAM chips and it should be possible to remove these from the PCB and read them in an EPROM programmer, possibly with an appropriate adapter.

Decoding the software would not be a trivial exercise and it might be better to look into the contents of the 8-pin EEPROM chip (next to the 10-pinconnector) first. This may contain configuration information that accounts for the differences in operation between your PCBs. You may be able to clone the configuration contents of a working PCB and reprogram them into the EEPROM chips on the other PCBs.

[pgo]

Hi,
It is possible that the 10-pin port is a BDM interface.  See:
https://www.nxp.com/products/processors-and-microcontrollers/legacy-mpu-mcus/32-bit-coldfire-mcus-mpus/68k-processors-legacy/m683xx/32-bit-microcontroller:MC68331
and more specifically:
Section 5.10.2.8 Recommended BDM Connection of the manual at
https://www.nxp.com/docs/en/reference-manual/MCCIRM.pdf
in theory it would be possible to access and control the MCU through this interface,
Access to the memory (EPROM etc) may (again in theory) be obtained via the MCU.
This would require the following:

• Suitable BDM interface (these are expensive/unavailable?)
• Extensive knowledge of the chip architecture
• Lots of time

If the above doesn't appear familiar to you I would not recommend this approach.
Good Luck!
bye

[joeqsmith]

This chip is part of communications gateway. I have 4 of them, so there might be several possible takes.
I don't know the feasibility of the project - what I would like to do is enable baud rate on three of the communication gateway devices (physically present, dip switches, but do not respond to toggle), and on the one that does have the baud rate enabled I need to enable an option that is already enabled on the other three.

There is a ten pin port that is connected the MCU, but if other pins access needed I can solder/connect to it. So there are no limits to how I have to connect to it, it depends on anyone's experience/ability on this forum. If there is no one who played with these MCUs, then it is a dead project for me!

So you just want to mirror the one to the other three.  Do you have the schematics?   If so, certainly possible.

Assuming port is the BDM (makes sense it would be) then it could most likely all be done through that test port.