54.4.5.1.2 Data Processing

To process data using XTS mode, follow the steps below:

1. Set AES_MR.OPMODE to XTS.
2. Write the Key1.
3. Only if the data to process is the first to be processed in the data unit, or if the data block to process is not consecutive to the previous processed data block in the same data unit, then two additional mandatory steps are required:

   a. AES_TWRx must be written with the encrypted Tweak Value (see Encrypted Tweak Generation for details) with bytes swapped as described in AES Register Endianness.

   b. Write AES_ALPHARx with the alpha primitive corresponding to the block number in the data unit.

4. Fill AES_IDATARx.IDATA with the data to process according to the SMOD configuration used. If Manual mode or Auto mode is used, the DATRDY bit indicates when the data have been processed and can be read in AES_ODATARx. Repeat Step 4 as long as consecutive data blocks are processed in the same data unit.