ARM r1p3, R4F C6, MPU Memory Region Number Register, Access data permission bit encoding, Unp

			System Control Coprocessor
		Table 4-34 Access data permission bit encoding (continued)
AP bit values	Privileged permissions	User permissions	Description
b011	Read/write	Read/write	Full access
b100	UNP	UNP	Reserved
b101	Read-only	No access	Privileged read-only
b110	Read-only	Read-only	Privileged/User read-only
b111	UNP	UNP	Reserved

To access the MPU Region Access Control Registers read or write CP15 with:

MRC p15, 0, <Rd>, c6, c1, 4 ; Read Region access control Register

MCR p15, 0, <Rd>, c6, c1, 4 ; Write Region access control Register

To execute instructions in User and Privileged modes:

•the region must have read access as defined by the AP bits

•the XN bit must be set to 0.

c6, MPU Memory Region Number Register

The MPU Region Registers are multiple registers with one register for each memory region implemented. The value contained in the MPU Memory Region Number Register determines which of the multiple registers is accessed.

The MPU Memory Region Number Registers are:

•read/write register

•accessible in Privileged mode only.

Figure 4-37shows the arrangement of bits in the register.

31 4 3 0

Reserved

Region

Figure 4-37 MPU Memory Region Number Register format

Table 4-35shows how the bit values correspond with the MPU Memory Region Number Register bits.

		Table 4-35 MPU Memory Region Number Register bit functions
Bits	Field	Function
[31:4]	Reserved	SBZ.
[3:0]	Region	Defines the group of registers to be accessed. Read the MPU Type Register to determine the number
		of supported regions, see c0, MPU Type Register on page 4-17.

To access the MPU Memory Region Number Register, read or write CP15 with:

MRC p15, 0, <Rd>, c6, c2, 0 ; Read MPU Memory Region Number Register

MCR p15, 0, <Rd>, c6, c2, 0 ; Write MPU Memory Region Number Register

Writing this register with a value greater than or equal to the number of regions from the MPU Type Register is Unpredictable. Associated register bank accesses are also Unpredictable.

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