54.4.3.1.1 If AES_MR.LOD = 0
The DATRDY flag is cleared when at least one AES_ODATARx is read (see the following figure).
If the user does not want to read AES_ODATARx between each encryption/decryption, the DATRDY flag will not be cleared. If the DATRDY flag is not cleared, the user cannot know the end of the following encryptions/decryptions.