Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
631
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
When processing completes, the DATRDY flag in the AES Interrupt Status Register (AES_ISR) is raised. If
an interrupt has been enabled by setting the DATRDY bit in the AES_IER, the interrupt line of the AES is
activated.
an interrupt has been enabled by setting the DATRDY bit in the AES_IER, the interrupt line of the AES is
activated.
When the software reads one of the AES_ODATARx, the DATRDY bit is automatically cleared.
31.4.3.2 Auto Mode
The Auto Mode is similar to the manual one, except that in this mode, as soon as the correct number of
AES_IDATARx
is written, processing is automatically started without any action in the AES_CR.
31.4.3.3 DMA Mode
The DMA Controller can be used in association with the AES to perform an encryption/decryption of a buffer
without any action by the software during processing.
without any action by the software during processing.
The SMOD field of the AES_MR must be set to 0x2 and the DMA must be configured with non incremental
addresses.
addresses.
The start address of any transfer descriptor must be set to AES_IDATAR0.
The DMA chunk size configuration depends on the AES mode of operation and is listed in
When writing data to AES with a first DMA channel, data are first fetched from a memory buffer (source data). It is
recommended to configure the size of source data to “words” even for CFB modes. On the contrary, the
destination data size depends on the mode of operation. When reading data from the AES with the second DMA
channel, the source data is the data read from AES and data destination is the memory buffer. In this case, source
data size depends on the AES mode of operation and is listed in
recommended to configure the size of source data to “words” even for CFB modes. On the contrary, the
destination data size depends on the mode of operation. When reading data from the AES with the second DMA
channel, the source data is the data read from AES and data destination is the memory buffer. In this case, source
data size depends on the AES mode of operation and is listed in
31.4.4 Last Output Data Mode
This mode is used to generate cryptographic checksums on data (MAC) by means of cipher block chaining
encryption algorithm (CBC-MAC algorithm for example).
encryption algorithm (CBC-MAC algorithm for example).
After each end of encryption/decryption, the output data are available either on the AES_ODATARx for Manual
and Auto mode or at the address specified in the receive buffer pointer for DMA mode (See
and Auto mode or at the address specified in the receive buffer pointer for DMA mode (See
).
The Last Output D ata bit (LOD) in the A ES_MR allows retrieval of only the last data of s everal
encryption/decryption processes.
encryption/decryption processes.
Therefore, there is no need to define a read buffer in DMA mode.
This data are only available on the AES_ODATARx.
Table 31-3.
DMA Data Transfer Type for the Different Operation Modes
Operation Mode
Chunk Size
Destination/Source Data Transfer Type
ECB
4
Word
CBC
4
Word
OFB
4
Word
CFB 128-bit
4
Word
CFB 64-bit
1
Word
CFB 32-bit
1
Word
CFB 16-bit
1
Half-word
CFB 8-bit
1
Byte
CTR
4
Word