Some control register sets always require a secure transaction. All other register sets are protected by the XPPU protection unit except the SATA, PCIe, and GPU register sets are protected by the FPD_XMPU.
•XPPU protected (majority of registers).
•XMPU protected (SIOU controller registers).
•Hardware protected (always secure registers).
The security protections for the register sets are listed with their addresses in Table: System-level Register Sets.