How enable Trust Zone to run the trusted application in ARM Cortex M3.
TrustZone is a feature of Armv8-M based microcontrollers. The Arm Cortex-M3 is a Armv7-based device. So you need a Cortex-M23/33/55/85 based device. Please also note that not every Armv8-M based device is TrustZone enabled. Check with the MCU vendor if TrustZone is implemented in a specific device.
Thanks Hans
How to enable or add TrustZone in case the vendor didn't enabled it on Cortex-M23/33/55/85 based device?
Is it possible to add TrustZone (software based) in Cortex-M3?
TrustZone for Cortex-M was added in Armv8-M architecture. The processors you mention at Armv7-M. See the following links for more information:
https://www.arm.com/technologies/trustzone-for-cortex-m
https://developer.arm.com/Processors/TrustZone%20for%20Cortex-M
Regards, Ronan