Part Number: SW-TM4C
Tool/software: Code Composer Studio
Hello. I made a new board with tiva c MCU. Now i need to protect whole firmware of reading via debug port. I try next code, but it crash execution.
FlashProtectSet(0, FlashExecuteOnly));
FlashProtectSave();
How to do it correctly?
To use "FlashExecuteOnly" you have to tell the compiler not to embed constants in the .text section. You do that in the "ARM Compiler", "Advanced Options", "Runtime Model Options" page of the build settings as shown below:
Then you need to modify the linker command file so that the .text section goes into flash that is execute only, but .const, .cinit, .pinit and .init_array sections are in flash that can be read.
Then at the end I suggest you add near the beginning of your program code to configure the JTAG pins as GPIO. That will make it even more difficult for someone to examine what is in the part.
Here is a really old application note that talks about using Execute-only memory. You need to disregard a lot of information on the older versions of the tools that were used nine years ago.
