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7: Memory Management Unit
7-18 EPSON ARM720T CORE CPU MANUAL
Table 7-10 shows how to interpret the
Access Permission
(AP) bits and how their
interpretation is dependent on the S and R bits (control register bits 8 and 9).
Table 7-11 Interpreting access permission (AP) bits
AP S R
Supervisor
permissions
User permissions Description
b00 0 0 No access No access Any access generates a
permission fault
b00 1 0 Read-only No access Only Supervisor read
permitted
b00 0 1 Read-only Read-only Any write generates a
permission fault
b00 1 1 Reserved - -
a
a. Do not use this encoding. [S:R] = b11 generates a fault for any access.
b01 x x Read/write No access Access allowed only in
Supervisor mode
b10 x x Read/write Read-only Writes in User mode cause
permission fault
b11 x x Read/write Read/write All access types permitted in
both modes
bxx 1 1 Reserved - -
a