R2: translation table base register, R3:domain access control register, Register format – Digi NS9215 User Manual
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W O R K I N G W I T H T H E C P U
R2: Translation Table Base register
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R 2 : T r a n s l a t i o n T a b l e B a s e r e g i s t e r
Register R2 is the Translation Table Base register (TTBR), for the base address of the
first-level translation table.
Reading from R2 returns the pointer to the currently active first-level
translation table in bits [31:14] and an
UNPREDICTABLE
value in bits [13:0].
Writing to R2 updates the pointer to the first-level translation table from the
value in bits[31:14] of the written value. Bits [13:0]
SHOULD BE ZERO
.
Use these instructions to access the Translation Table Base register:
MRC p15, 0, Rd, c2, c0, 0; read TTBR
MCR p15, 0, Rd, c2, c0, 0; write TTBR
The
CRm
and
opcode_2
fields
SHOULD BE ZERO
when writing to R2.
Register format
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R 3 : D o m a i n A c c e s s C o n t r o l r e g i s t e r
Register R3 is the Domain Access Control register and consists of 16 two-bit fields.
Reading from R3 returns the value of the Domain Access Control register.
Writing to R3 writes the value of the Domain Access Control register.
Register format
Access
permissions and
instructions
Each two-bit field defines the access permissions for one of the 16 domains
(D15–D0):
00
No access: Any access generates a domain fault
01
Client: Accesses are checked against the access permission bits in the section or page descriptor
10
Reserved: Currently behaves like no access mode (00)
11
Manager: Accesses are not checked against the access permission bits, so a permission fault
cannot be generated.
Use these instructions to access the Domain Access Control register:
MRC p15, 0, Rd, c3, c0, 0; read domain access permissions
MCR p15, 0, Rd, c3, c0, 0; write domain access permissions
31
0
14 13
Translation table base
UNP/SBZ
31
0
14 13 12 11 10
9
8
7
6
5
4
3
2
1
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15