CCS/MSP430F5529: USB Freeze issue

Have tried the following code and the debugger jumps to this location, but it does not reawaken the processor.

//general interrupt handling

#pragma vector=unused_interrupts
__interrupt void user_trap_function(void)
{ // code for handling all interrupts that do not have // specific ISRs
    __bic_SR_register_on_exit(LPM3_bits);   // Exit LPM0-3
            __no_operation();  // Required for debugger
}

Hello,

The user_trap_function is the default interrupt service routine. If you enable a peripheral interrupt but without defining your own ISR, then the interrupt process will enter the default ISR.

Thanks very much for your response Winter.

I am using USB code from the LaunchPad Demo board, so there may well be interrupts enabled that I am not aware of. 

I have added the below code, and the debugger ends up at the NOP when the micro freezes, so this does work, however, it does not exit this routine. Do you have any suggestions?

//general interrupt handling

#pragma vector=unused_interrupts
__interrupt void user_trap_function(void)
{ // code for handling all interrupts that do not have // specific ISRs
    __bic_SR_register_on_exit(LPM3_bits);   // Exit LPM0-3
            __no_operation();  // Required for debugger
}

Could you check the registers to see if any interrupt IFG and IE is set?

As far as I can see, the Function Resume register is set when the micro freezes.

RESRIFG 1 USB - Function Resume Request Interrupt Flag 

Could you disable this interrupt?