Manual Mode

The sequence of actions is as follows:

  1. 1.Write AES_MR with all required fields, including but not limited to SMOD and OPMOD.
  2. 2.Write the 128-bit/192-bit/256-bit AES key in AES_KEYWRx.
  3. 3.Write the initialization vector (or counter) in AES_IVRx.

    Note: AES_IVRx concerns all modes except ECB.

  4. 4.Set the bit DATRDY (Data Ready) in the AES Interrupt Enable register (AES_IER), depending on whether an interrupt is required or not at the end of processing.
  5. 5.Write the data to be encrypted/decrypted in the authorized AES_IDATARx (see the table below).
  6. 6.Set the START bit in the AES Control register (AES_CR) to begin the encryption or the decryption process.
  7. 7.When processing completes, the DATRDY flag in the AES Interrupt Status register (AES_ISR) is raised. If an interrupt has been enabled by setting AES_IER.DATRDY, the interrupt line of the AES is activated.
  8. 8.When software reads one of AES_ODATARx, AES_IER.DATRDY is automatically cleared.
Table 1. Authorized Input Data Registers
Operating Mode Input Data Registers to Write
ECB All
CBC All
OFB All
128-bit CFB All
64-bit CFB AES_IDATAR0 and AES_IDATAR1
32-bit CFB AES_IDATAR0
16-bit CFB AES_IDATAR0
8-bit CFB AES_IDATAR0
CTR All
GCM All
Notes:
  1. 1.In 64-bit CFB mode, writing to AES_IDATAR2 and AES_IDATAR3 is not allowed and may lead to errors in processing.
  2. 2.In 32, 16, and 8-bit CFB modes, writing to AES_IDATAR1, AES_IDATAR2 and AES_IDATAR3 is not allowed and may lead to errors in processing.
Parent topic: Start Modes