System Control
ARM DDI 0363G Copyright © 2006-2011 ARM Limited. All rights reserved. 4-54
ID073015 Non-Confidential
Table 4-32 shows the MPU Region Size and Enable Registers bit assignments.
To access an MPU Region Size and Enable Register, read or write CP15 with:
MRC p15, 0, <Rd>, c6, c1, 2 ; Read Data MPU Region Size and Enable Register
MCR p15, 0, <Rd>, c6, c1, 2 ; Write Data MPU Region Size and Enable Register
Writing a region size that is outside the range results in Unpredictable behavior.
c6, MPU Region Access Control Registers
The MPU Region Access Control Register characteristics are:
Purpose Holds the region attributes and access permissions for the region specified
by the Memory Region Number Register.
Usage constraints The MPU Region Access Control Registers are:
• read/write registers
• accessible in Privileged mode only.
Configurations Use these registers if the processor is configured with an MPU.
Attributes See Table 4-33 on page 4-55.
Figure 4-35 on page 4-55 shows the MPU Region Access Control Registers bit assignments.
Table 4-32 Region Size MPU Region Size and Enable Registers bit assignments
Bits Name Function
[31:16] - SBZ.
[15:8] Sub-region disable
Each bit position represents a sub-region, 0-7
a
.
Bit [8] corresponds to sub-region 0
...
Bit [15] corresponds to sub-region 7
The meaning of each bit is:
0
= address range is part of this region
1
= address range is not part of this region.
-SBZ.
[5:1] Region size Defines the region size:
b00000
-
b00011
=Unpredictable
b00100
= 32 bytes
b00101
= 64 bytes
b00110
= 128 bytes
b00111
= 256 bytes
b01000
= 512 bytes
b01001
= 1KB
b01010
= 2KB
b01011
= 4KB
b01100
= 8KB
b01101
= 16KB
b01110
= 32KB
b01111
= 64KB
b10000
= 128KB
b10001
= 256KB
b10010
= 512KB
b10011
= 1MB
b10100
= 2MB
b10101
= 4MB
b10110
= 8MB
b10111
= 16MB
b11000
= 32MB
b11001
= 64MB
b11010
= 128MB
b11011
= 256MB
b11100
= 512MB
b11101
= 1GB
b11110
= 2GB
b11111
= 4GB.
[0] Enable Enables or disables a memory region:
0
= Memory region disabled. Memory regions are disabled on reset.
1
= Memory region enabled. A memory region must be enabled before it is used.
a. Sub-region 0 covers the least significant addresses in the region, while sub-region 7 covers the most significant
addresses in the region. For more information, see Subregions on page 7-3.
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