As shown in the picture, the monitor can be viewed as a software layer that lies between Trust/Non-trust worlds and underlying hardware. The monitor is responsible for:

* enabling and initializing TrustZone in order to protect memory regions that must not be accessible by Non-secure world

About operating systems, Linux has been chosen for Non-trust world, while [http://www.freertos.org FreeRTOS ] has been selected for the Trust world. At the time of this design, the Linux/FreeRTOS combination has proven to be the most appealing for the majority of applications that this solution addresses. Nevertheless different combinations are possible{{efn|For example TOPPERS project makes use of [http://www.toppers.jp/en/index.html different RTOSes].}}.