MPU Memory Management Unit
2-42
2.7.9
Domain Access Control
MMU accesses are primarily controlled via domains. There are 16 domains,
and each domain has a 2-bit field to define it. Two kinds of users are supported:
clients and managers. Clients use a domain; managers control the behavior
of the domain. The domains are defined in the domain access control register.
The following figure illustrates how the 32 bits of the register are allocated to
define the sixteen 2-bit domains.
Figure 2–19. Domain Access Control Register Format
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
Table 2–24 defines how the bits within each domain are interpreted to specify
the access permissions.
Table 2–24. Interpreting Access Bits in Domain Access Control Register
Value
Access Type
Description
0b00
No access
Any access generates a domain fault.
0b01
Client
Access permission is checked against the permission
given by the page descriptor.
0b10
Reserved
Behaves like no access
0b11
Manager
The access permission is not checked; permission
faults are not generated.