ARM Cortex R4F - Manual (Page 136)

System Control Coprocessor
ARM DDI 0363E Copyright © 2009 ARM Limited. All rights reserved. 4-52
ID013010 Non-Confidential, Unrestricted Access
The MPU Region Access Control Registers are:
•
read/write registers
• accessible in Privileged mode only.
Figure 4-36 shows the arrangement of bits in the register.
Figure 4-36 MPU Region Access Control Register format
Table 4-33 shows how the bit values correspond with the Region Access Control Register
functions.
Table 4-34 shows the AP bit values that determine the permissions for Privileged and User data
access.
Reserved B C
31 3 0
TEX S
1 2 5 6 7 8 11 10 12
XN AP
Reserved
13
Table 4-33 MPU Region Access Control Register bit functions
Bits Field Function
[31:13] Reserved SBZ.
[12] XN Execute never. Determines if a region of memory is executable:
0 = all instruction fetches enabled
1 = no instruction fetches enabled.
[11] - Reserved.
[10:8] AP Access permission. Defines the data access permissions. For more information on AP bit values
see, Table 4-34.
[7:6] Reserved SBZ.
[5:3] TEX Type extension. Defines the type extension attribute a .
[2] S Share. Determines if the memory region is Shared or Non-shared:
0 = Non-shared.
1 = Shared.
This bit only applies to Normal, not Device or Strongly Ordered memory.
[1] C C bit a :
[0] B B bit a :
a. For more information on this region attribute, see Table 7-3 on page 7-9.
Table 4-34 Access data permission bit encoding
AP bit values Privileged permissions User permissions Description
b000 No access No access All accesses generate a permission fault
b001 Read/write No access Privileged access only
b010 Read/write Read-only Writes in User mode generate permission
faults