I am currently porting an application from LM3S6965 to Tiva LM4C129X using the DK-TM4C129X-Kit. As I have quite frequent problem with the debugger (receiving fault interrupts) whereas the application is working fine without debugger, I went back to the start, examining the sample application enet_lwip. The only change I did was to switch off optimization.
If I start the application within the debugger, it works. If I stop it, press "restart" and start it again, there is no SYSTICK interrupt anymore. If I examine the NVIC registers, there is no pending interrupt, SYSTICK is running, interrupt is enabled. In xPSR, the EXCEPTION bits are set to 11H (PORT B = USB?).
If I repeat the "restart" sequence several times, I get into a mode, in which "restart" never returns. Pressing "Pause" ends up somewhere in "boot.asm". The only way to get out, is to exit the debugger and press the "reset" button.
Another effect is that whenever exiting the debugger, the virtual UART-port (FTDI driver in Windows) does not find a device anymore. The only way to get it back is to reboot Windows.
Is this a known issue? A problem of the Windows driver, the debugger, the hardware or something else? I am running CCS 6.0.1 on a Windows 7 PC with all updates installed.