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TM4C123AE6PM: Unknown state without debugger

Norbert Toth
Expert 1145 points
Part Number: TM4C123AE6PM


Hi Folks,

I have a custome developed board based on the CPU type in the subject. I have been investigating this issue for several weeks without any success.  Even I cannot decide if it is a hardware or firmware problem, any combination the them or whatever...

So basically the test firmware wait on receiving SPI data and puts it onto GPIO, where a LED visualize this normal operation. As I saw, it works very well if my computer is connected to the board via ICDI. If I pull out the USB of the ICDI, the firmware stops, everything stops so I have to do a power cycle to be able to connect to the target again from CCS. It means, that I cannot use the debugger to see where is the execution lost...

The CPU isn't starts without ICDI connected to it.

I investigated the power supply by oscilloscope, but everything was OK. On the image you can see the related parts of  the board (oscillator, filter capacitors, JTAG)

Can anybody help me, how can I detect this issue?

  • 0
    TI__Guru 72500 points
    With the JTAG attached, double check that you have the reset stack pointer and reset vector programmed into locations 0x0 and 0x4. When you load symbols (or load the program) the debugger automatically sets the PC to the entry point, so it might work with the debugger attached even if the reset vector is missing.