Table 9-4 Mpu Region Number Register Bit Assignments; Figure 9-3 Mpu Region Number Register Bit Assignments - ARM Cortex-M3 Technical Reference Manual

31
Bits Field Function
[31:8] - Reserved.
[7:0] REGION Region select field. Selects the region to operate on when using the Region Attribute and Size
Register and the Region Base Address Register. It must be written first except when the address
VALID + REGION fields are written, which overwrites this.
ARM DDI 0337G
Unrestricted Access
Table 9-4 describes the bit assignments of the MPU Region Number Register.
MPU Region Base Address Register
Use the MPU Region Base Address Register to write the base address of a region. The
Region Base Address Register also contains a REGION field that you can use to
override the REGION field in the MPU Region Number Register, if the VALID bit is
set.
The Region Base Address register sets the base for the region. It is aligned by the size.
So, a 64-KB sized region must be aligned on a multiple of 64KB, for example,
or
0x00010000 0x00020000
The region always reads back as the current MPU region number. VALID always reads
back as 0. Writing with VALID = 1 and REGION = n changes the region number to n.
This is a short-hand way to write the MPU Region Number Register.
This register is Unpredictable if accessed other than as a word.
The register address, access type, and Reset state are:
Address
0xE000ED9C
Access Read/write
Reset state Unpredictable
Figure 9-4 on page 9-8 shows the bit assignments of the MPU Region Base Address
Register.
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Reserved

Figure 9-3 MPU Region Number Register bit assignments

Table 9-4 MPU Region Number Register bit assignments

.
Non-Confidential
Memory Protection Unit
8 7 0
REGION
9-7