56.4.5.4 Register Write Protection

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

If a write access to the protected registers is detected, the WPVS flag in the TDES Write Protection Status Register (TDES_WPSR) is set and the field WPVSRC indicates the register in which the write access has been attempted.

The WPVS flag is automatically cleared by reading TDES_WPSR.

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

• TDES Mode Register
• TDES Key 1 Word Register x
• TDES Key 2 Word Register x
• TDES Key 3 Word Register x
• TDES Initialization Vector Register x
• TDES XTEA Rounds Register

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

• TDES Interrupt Enable Register
• TDES Interrupt Disable Register

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

• TDES Control Register