Table 9-9 Cache Policy For Memory Attribute Encoding; Table 9-10 Ap Encoding; Table 9-11 Xn Encoding - ARM Cortex-M3 Technical Reference Manual

Memory Protection Unit
AP[2:0] Privileged permissions
000 No access
001 Read/write
010 Read/write
011 Read/write
100 Unpredictable
101 Read only
110 Read only
111 Read only
9-14
Table 9-9 describes the cache policy for memory attribute encoding.
Memory attribute encoding (AA and BB)
00
01
10
11
Note
All cache policies presented by HPROT and MEMATTR relate to an outer cache.
Table 9-10 describes the AP encoding.
User permissions
No access
No access
Read only
Read/write
Unpredictable
No access
Read only
Read only
Table 9-11 describes the XN encoding.
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Table 9-9 Cache policy for memory attribute encoding

Descriptions
All accesses generate a permission fault
Privileged access only
Writes in user mode generate a permission fault
Full access
Reserved
Privileged read only
Privileged/user read only
Privileged/user read only
Non-Confidential
Cache policy
Non-cacheable
Write back, write and read allocate
Write through, no write allocate
Write back, no write allocate

Table 9-10 AP encoding

Table 9-11 XN encoding

XN Description
0 All instruction fetches enabled
1 Instruction fetches disabled
ARM DDI 0337G
Unrestricted Access