52.5.3.4 Register Write Protection

To prevent any single software error from corrupting TZAESB behavior, certain registers in the address space can be write-protected by setting WPEN (Write Protection Enable), WPITEN (Write Protection Interrupt Enable), and/or WPCREN (Write Protection Control Enable) in the TZAESB Write Protection Mode register (TZAESB_WPMR).

If a write access to a write-protected register is detected, the Write Protection Violation Status (WPVS) flag in the TZAESB Write Protection Status register (TZAESB_WPSR) is set and Write Protection Violation Source (WPVSRC) indicates the register in which the write access has been attempted.

WPVS is automatically cleared after reading TZAESB_WPSR.

The following registers can be write-protected when WPEN is set in TZAESB_WPMR:

• TZAESB Mode Register
• TZAESB Key Word Register x
• TZAESB Initialization Vector Register x
• TZAESB Extended Mode Register

The following registers can be write-protected when WPITEN is set:

• TZAESB Interrupt Enable Register
• TZAESB Interrupt Disable Register

The following register can be write-protected when WPCREN is set:

• TZAESB Control Register