ST X-CUBE-SBSFU, User Manual, Page: 63 / 94

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UM2262 Secure Engine protected environment
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Figure 33. Secure Engine interface
SE interface mechanism simplifies the control access to the call gate independent from user
implementation. SE interface APIs are shared with the user application, which therefore
executes sensitive operations (if not locked via the Secure Engine lock service) in a secure
way using the services provided by SE.
A.2 MPU-based Secure Engine Isolation
A.2.1 Principle
The MPU-based Secure Engine isolation relies on the concept of privileged and
unprivileged levels of software execution. The software must run in unprivileged level of
execution by default (when SBSFU or the User Application is running), except for very
specific actions like platform initialization or interrupt handling. This is described in
Figure 34 .