The processor has a lock-up state that is entered when an
unrecoverable condition occurs. The cause of unrecoverable conditions
are asynchronous or synchronous faults, including an escalated
For more information on unrecoverable conditions, see the ARMv6-M
Architecture Reference Manual.
The processor can enter the lock-up state at a priority of -1 or -2. An NMI can be taken and cause the processor to leave the lock-up state if it was at a priority of -1.
A debugger can also cause the processor to exit the lock-up state.
The LOCKUP pin from the processor indicates the that the processor is in the lock-up state.