ARM Cortex-M4 - MPU_RBAR Bit Assignments; MPU Region Attribute and Size Register; The ADDR Field

Cortex-M4 Peripherals
ARM DUI 0553A Copyright © 2010 ARM. All rights reserved. 4-41
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Write MPU_RBAR with the VALID bit set to 1 to change the current region number and update
the MPU_RNR. The bit assignments are:
The ADDR field
The ADDR field is bits[31:N] of the MPU_RBAR. The region size, as specified by the SIZE
field in the MPU_RASR, defines the value of N:
N = Log
2
(Region size in bytes),
If the region size is configured to 4GB, in the MPU_RASR, there is no valid ADDR field. In
this case, the region occupies the complete memory map, and the base address is
0x00000000 .
The base address is aligned to the size of the region. For example, a 64KB region must be
aligned on a multiple of 64KB, for example, at
0x00010000 or 0x00020000 .
4.5.5 MPU Region Attribute and Size Register
The MPU_RASR defines the region size and memory attributes of the MPU region specified by
the MPU_RNR, and enables that region and any subregions. See the register summary in
Table 4-38 on page 4-38 for its attributes.
MPU_RASR is accessible using word or halfword accesses:
• the most significant halfword holds the region attributes
• the least significant halfword holds the region size and the region and subregion enable
bits.
VALID
ADDR
31 N N-1 5 4 3 0
Reserved REGION
If the region size is 32B, the ADDR field is bits [31:5] and there is no Reserved field
Table 4-42 MPU_RBAR bit assignments
Bits Name Function
[31:N] ADDR Region base address field. The value of N depends on the region size. For more information see
The ADDR field.
[(N-1):5] - Reserved.
[4] VALID MPU Region Number valid bit:
Write:
0 = MPU_RNR not changed, and the processor:
• updates the base address for the region specified in the MPU_RNR
• ignores the value of the REGION field
1 = the processor:
• updates the value of the MPU_RNR to the value of the REGION field
• updates the base address for the region specified in the REGION field.
Always reads as zero.
[3:0] REGION MPU region field:
For the behavior on writes, see the description of the VALID field.
On reads, returns the current region number, as specified by the RNR.