SWCU194 March 2023 CC1314R10 , CC1354P10 , CC1354R10 , CC2674P10 , CC2674R10
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 enters Thread mode on reset, or as a result of an exception return to Thread mode. Privileged and Unprivileged code can run in Thread mode.
The processor enters Handler mode as a result of an exception. All code is privileged in Handler mode.
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.