40.4.3.2.2 If AES_MR.LOD = 1
This mode is optimized to process AES CBC-MAC operating mode.
The user must first wait for the AES_ISR.ENDTX (or AES_ISR.TXBUFE) flag to be raised, then for DATRDY to ensure that the encryption/decryption is completed (see the following figure).
The PDC receive channel must not be used. Prior to reading the CBC-MAC result, AES_MR.SMOD must be written to 0. To restart a CBC-MAC on a new buffer, AES_MR.SMOD must be written to 2.
The output data are only available on AES_ODATARx.
The following table summarizes the different cases.
| Sequence | Manual and Auto Modes | PDC Mode | ||
|---|---|---|---|---|
| AES_MR.LOD = 0 | AES_MR.LOD = 1 | AES_MR.LOD = 0 | AES_MR.LOD = 1 | |
| DATRDY Flag Clearing Condition(1) | At least one AES_ODATAR must be read | At least one AES_IDATAR must be written | Not used | Managed by the PDC |
| End of Encryption/Decryption Notification | DATRDY | DATRDY | ENDRX (or RXBUFF) | ENDTX (or TXBUFE) then DATRDY |
| Encrypted/Decrypted Data Result Location | In AES_ODATARx | In AES_ODATARx | At the address specified in AES_RPR | In AES_ODATARx |
Note: Depending on the mode, there are other
ways of clearing the AES_ISR.DATRDY flag. See AES_ISR.
Warning: In PDC mode, reading
AES_ODATARx before the last data transfer may lead to unpredictable results.