DocID018909 Rev 11
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RM0090
Cryptographic processor (CRYP)
757
23.6.12 CRYP context swap registers (CRYP_CSGCMCCM0..7R and
CRYP_CSGCM0..7R) for STM32F42xxx and STM32F43xxx
Address offset:
•
CRYP_CSGCMCCM0..7: 0x050 to 0x06C: used for GCM/GMAC or CCM/CMAC
alogrithm only
•
CRYP_CSGCM0..7: 0x070 to 0x08C: used for GCM/GMAC algorithm only
Reset value: 0x0000 0000
These registers contain the complete internal register states of the CRYP processor when
the GCM/GMAC or CCM/CMAC algorithm is selected. They are useful when a context swap
has to be performed because a high-priority task needs the cryptographic processor while it
is already in use by another task.
When such an event occurs, the CRYP_CSGCMCCM0..7R and CRYP_CSGCM0..7R (in
GCM/GMAC mode) or CRYP_CSGCMCCM0..7R (in CCM/CMAC mode) registers have to
be read and the values retrieved have to be saved in the system memory space. The
cryptographic processor can then be used by the preemptive task, and when the
cryptographic computation is complete, the saved context can be read from memory and
written back into the corresponding context swap registers.
Note:
These registers are used only when GCM/GMAC or CCM/CMAC algorithm mode is
selected.
CRYP_CSGCMCCMxR: where x=[7:0]
CRYP_CSGCMxR: where x=[7:0]
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
CRYP_CSGCMCCMxR
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
CRYP_CSGCMCCMxR
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
CRYP_CSGCMxR
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
CRYP_CSGCMxR
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw