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NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
- 975 -
Revision V1.30
NUC97
0
T
E
CHNIC
A
L
RE
F
E
RE
N
CE
MA
NUA
L
AES Byte Count Register (CRPT_AES0_CNT, CRPT_AES1_CNT, CRPT_AES2_CNT,
CRPT_AES3_CNT)
Register
Offset
R/W
Description
Reset Value
CRPT_AES0_CNT
0x148 R/W
AES Byte Count Register for Channel 0
0x0000_0000
CRPT_AES1_CNT
0x184 R/W
AES Byte Count Register for Channel 1
0x0000_0000
CRPT_AES2_CNT
0x1C0 R/W
AES Byte Count Register for Channel 2
0x0000_0000
CRPT_AES3_CNT
0x1FC R/W
AES Byte Count Register for Channel 3
0x0000_0000
31
30
29
28
27
26
25
24
CNT
23
22
21
20
19
18
17
16
CNT
15
14
13
12
11
10
9
8
CNT
7
6
5
4
3
2
1
0
CNT
Bits
Description
[31:0]
CNT
AES Byte Count
The CRPT_AESn_CNT keeps the byte count of source text that is for the AES engine
operating in DMA mode. The CRPT_AESn_CNT is 32-bit and the maximum of byte count is
4G bytes.
CRPT_AESn_CNT can be read and written. Writing to CRPT_AESn_CNT while the AES
accelerator is operating
doesn’t affect the current AES operation. But the value of
CRPT_AESn_CNT will be updated later on. Consequently, software can prepare the byte
count of data for the next AES operation.
According to CBC-CS1, CBC-CS2, and CBC-CS3 standard, the count of operation data must
be at least one block. Operations that are less than one block will output unexpected result.
In Non-DMA ECB, CBC, CFB, OFB, and CTR mode, CRPT_AESn_CNT must be set as byte
count for the last block of data before feeding in the last block of data. In Non-DMA CBC-CS1,
CBC-CS2, and CBC-CS3 mode, CRPT_AESn_CNT must be set as byte count for the last two
blocks of data before feeding in the last two blocks of data.