PM0223 datasheet(104/110 Pages) STMICROELECTRONICS

104 / 110 page

STM32L0 Core Peripherals

PM0223

104/110

DocID025763 Rev 1

For information about access permission, see MPU access permission attributes on

page 104.

SIZE field values

The SIZE field defines the size of the MPU memory region specified by the MPU_RNR. as

follows:

(Region size in bytes) = 2(SIZE+1)

The smallest permitted region size is 256B, corresponding to a SIZE value of 7. Table 36

gives example SIZE values, with the corresponding region size and value of N in the

MPU_RBAR

4.5.6

MPU access permission attributes

This section describes the MPU access permission attributes. The access permission bits,

C, B, S, AP, and XN, of the MPU_RASR, control access to the corresponding memory

region. If an access is made to an area of memory without the required permissions, then

the MPU generates a permission fault.

Bits 26:24

AP[2:0]: Access permission field, see Table 38: AP encoding

Bits 23:19

Reserved, forced by hardware to 0.

Bit 18

S: Shareable bit see Table 37 on page 105

Bit 17

C: Cacheable bit see Table 38 on page 105

Bit 16

B: Bufferable bit, see Table 37 on page 105

Bits 15:8

SRD: Subregion disable bits.

For each bit in this field:

0 = Corresponding sub-region is enabled.

1 = Corresponding sub-region is disabled.

See Subregions on page 106 for more information.

Bits 7:6

Reserved, forced by hardware to 0.

Bits 5:1

SIZE: Size of the MPU protection region.

Specifies the size of the MPU region. The minimum permitted value is 7 (b00111). See SIZE

field values on page 104 for more information

Bit 0

ENABLE: Region enable bit(1).

1. The region enable bit of all regions is reset to 0. This enables you to only program regions you want enabled.

Table 36. Example SIZE field values

SIZE value

Region size

Value of N(1)

1. In the MPU_RBAR, see MPU Region Base Address Register on page 102.

Note

b00111 (7)

256B

Minimum permitted size.

b01001 (9)

1KB

b10011 (19)

1MB

b11101 (29)

1GB

b11111 (31)

4GB

Maximum possible size.

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