The aim of this article is to provide guideline for disabling Trustzone on STM32U5.
1. Hardware and software setup
- Nucleo MB1549-U5A5ZJT6Q1. Hardware and software setup
- STM32CubeProgrammer
As you can see when connecting your board to STM32CubeProgrammer and checking the option bytes, TZEN is checked (TrustZone® enabled).
2. Disable TrustZone®
To disable TrustZone®, you have to:
Step 1: Connect Boot0 to VDD on your board:
This consists on connecting PH3 pin (CN11 pin 7) to VDD (CN11 pin 5).
![1640.png 1640.png](/t5/image/serverpage/image-id/1738iDAF124232B655045/image-size/large?v=v2&px=999)
Step 2: Connect your board with STM32CubeProgrammer in "hot plug" Mode.
![1641.png 1641.png](/t5/image/serverpage/image-id/1740i497A3035A90E83E9/image-size/large?v=v2&px=999)
Step 3: Switch RDP value in “readout protection” to level 1, then click on apply.
![1642.png 1642.png](/t5/image/serverpage/image-id/1739i447723D56B5FAC60/image-size/large?v=v2&px=999)
Step 4:
- Switch RDP value to level 0
- Uncheck the TZEN value in user configuration.
![1643.png 1643.png](/t5/image/serverpage/image-id/1741i5833F9A6EE236207/image-size/large?v=v2&px=999)
Step 5: Then click on apply to program the option bytes.
![1644.png 1644.png](/t5/image/serverpage/image-id/1742i14520A6BA9A7A754/image-size/large?v=v2&px=999)
Step 6: Disconnect your board to STM32CubeProgrammer.
Step 7: Disconnect Boot0 to VDD.
Step 8: Connect again your board with STM32CubeProgrammer and make sure that TrustZone® is disabled(TZEN unchecked).
![1645.png 1645.png](/t5/image/serverpage/image-id/1745i618AE1BD37F83702/image-size/large?v=v2&px=999)
Reproduce this procedure faithfully otherwise the TrustZone® will not be disabled.