
RM0453 Rev 2
685/1454
RM0453
AES hardware accelerator (AES)
695
Bits 23:20
NPBLB[3:0]:
Number of padding bytes in last block
The bitfield sets the number of padding bytes in last block of payload:
0000: All bytes are valid (no padding)
0001: Padding for one least-significant byte of last block
...
1111: Padding for 15 least-significant bytes of last block
Bit 19 Reserved, must be kept at reset value.
Bit 18
KEYSIZE:
Key size selection
This bitfield defines the length of the key used in the AES cryptographic core, in bits:
0: 128
1: 256
Attempts to write the bit are ignored when the EN bit of the AES_CR register is set before the write
access and it is not cleared by that write access.
Bit 17 Reserved, must be kept at reset value.
Bit 15 Reserved, must be kept at reset value.
Bits 14:13
GCMPH[1:0]:
GCM or CCM phase selection
This bitfield selects the phase of GCM, GMAC or CCM algorithm:
00: Init phase
01: Header phase
10: Payload phase
11: Final phase
The bitfield has no effect if other than GCM, GMAC or CCM algorithms are selected (through the
ALGOMODE bitfield).
Bit 12
DMAOUTEN
: DMA output enable
This bit enables/disables data transferring with DMA, in the output phase:
0: Disable
1: Enable
When the bit is set, DMA requests are automatically generated by AES during the output data
phase. This feature is only effective when Mode 1 or Mode 3 is selected through the MODE[1:0]
bitfield. It is not effective for Mode 2 (key derivation).
Bit 11
DMAINEN
:
DMA input enable
This bit enables/disables data transferring with DMA, in the input phase:
0: Disable
1: Enable
When the bit is set, DMA requests are automatically generated by AES during the input data phase.
This feature is only effective when Mode 1 or Mode 3 is selected through the MODE[1:0] bitfield. It is
not effective for Mode 2 (key derivation).
Bit 10
ERRIE
: Error interrupt enable
This bit enables or disables (masks) the AES interrupt generation when RDERR and/or WRERR is
set:
0: Disable (mask)
1: Enable
Bit 9
CCFIE
: CCF interrupt enable
This bit enables or disables (masks) the AES interrupt generation when CCF (computation complete
flag) is set:
0: Disable (mask)
1: Enable