Epson ARM.POWERED ARM720T - Manual (Page 113)

7: Memory Management Unit
ARM720T CORE CPU MANUAL EPSON 7-17
7.6 Domain access control
MMU accesses are primarily controlled through the use of domains. There are 16 domains and
each has a 2-bit field to define access to it. Two types of user are supported, clients and
managers. The domains are defined in the Domain Access Control Register. Figure 7-13 shows
how the 32 bits of the register are allocated to define the 16 2-bit domains.
Figure 7-13 Domain Access Control Register format
Table 7-10 defines how the bits within each domain are interpreted to specify the access
permissions.
Table 7-10 Interpreting access control bits in Domain Access Control Register
Value Meaning Description
b00 No access Any access generates a domain fault
b01 Client Accesses are checked against the access
permission bits in the section or page descriptor
b10 Reserved Reserved. Currently behaves like the no access
mode
b11 Manager Accesses are not checked against the access
permission bits so a permission fault cannot be
generated
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0