How to decrypt ecu firmware?

Question

Programming

I opened the firmware in a disassembler, here is a screen:

Here is the second one:

On the second one there is one hexadecimal code, how to understand what it does and what exactly it is written for?

Answer 1

Get a disassembler for this particular microcontroller.

Answer 2

On the screen - IDA did not recognize the start code, therefore, the target processor was not specified in the options. (similar to MSC51, jump to LJMP 0213 at the start address)
First, read about IDA. A fairly powerful tool, but, I suppose, in your case, a disassembler for a specific MCU model will suffice.
Chris Kaspersky (RIP) wrote well about the IMU at one time
fox3264.narod.ru/olderfiles/1/Obraz_myshleniya_diz...

Answer 3

That's better in HEX.
1. From what address does it start?
Some start from 0000. Some take addresses from fffX (for interrupts and start address)
2. What is the first command? We look at the table of commands. How many operands does it have? We write on paper. What then?
That is also what the disassembler does. And then we optimize to SI. Then we try to understand what it does...
Add HEX and command table. And you can sort it out together :)