CCS/TMS320F28377D: C2000 real-time mode

I believe that error is occurring due to the Dual Code Security Module(CSM) being active.  One effect of the DCSM is that if code is executing from a protected region any debug access to the device will be blocked.

In order to debug your FW you will need to disable the DCSM, assuming your device is erased then you'll simply need to do a read of the CSMKEY registers.

http://www.ti.com/product/TMS320F28379D/datasheet/dual-code-security-module-sprs8809564#SPRS8809564

http://www.ti.com/lit/ug/spruhm8g/spruhm8g.pdf Section 2.13.3 and Section 2.13.3.3.1 has a small code example.

You can either add this to the beginning of your code, or do it from the debugger:

If from the debugger, you'll need to ensure that the processor is in a known area that is not protected so the debugger can communicate.  For this you will need to configure the boot pins to "Wait Boot" mode.  This will put the processor in a hold loop so that you can connect.  

http://www.ti.com/product/TMS320F28379D/datasheet/boot-rom-and-peripheral-booting-sprs8801514#SPRS8801514

Once this is done, you'll need to reset the MCU so that it re-reads the boot mode pins; you'll need to dis-able real-time mode when you reset the core, or that will kick a different error.

Now in the wait boot mode, you can do the dummy read of the password locations ref'd above and then you can restart at "Main" and debug with real time enabled.

Let me know if this gets you where you need to be in the debug process or there are still questions.

Best,

Matthew