SWRU626 December 2025 CC3501E , CC3551E
For each security state, the processor can operate in Thread or Handler mode. The conditions which cause the processor to enter Thread or Handler mode are as follows:
The processor can change security state on taking an exception, for example when a Secure exception is taken from Non-secure state, the Thread mode enters the Secure state Handler mode. The processor can also call Secure functions from Non-secure state and Non-secure functions from Secure state. The Security Extension includes requirements for these calls to prevent secure data from being accessed in Non-secure state.