Configuring PPB Area Access in the TEE Tool

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If you are using LPCSxx microcontrollers and the TEE tool for configuration of resources isolation, you may encounter a tool warning or the chip’s behaviour differs from the expectations. This article may help you in configuring the Private Peripheral Bus (PPB) area properly.

The 0xE000_0000 – 0xFFFF_FFFF area has specific behaviour in the TrustZone. The area’s security can be configured in the SAU, however, multiple regions are either exempt from security checking, or are fixed as Secure. Especially:

• 0xE000_0000 - 0xE000_2FFF – exempt from security violation checks
• 0xE000_E000 - 0xE000_EFFF – exempt from security violation checks
• 0xE002_E000 - 0xE002_EFFF – exempt from security violation checks
• 0xE004_0000 - 0xE004_1FFF – exempt from security violation checks
• 0xE00F_F000 - 0xE00F_FFFF – exempt from security violation checks
• 0xE000_0000 - 0xEFFF_FFFF – exempt from security violation checks for instruction fetch
• 0xF000_0000 – 0xFFFF_FFFF – fixed as Secure

Therefore if you configure any address range mentioned above as a Non-Secure region in the SAU, the TEE tool generates a warning.