CMSIS-Core (Cortex-M): MPU Functions for Armv7-M

| CMSIS-Core (Cortex-M) Version 5.1.2 CMSIS-Core support for Cortex-M processor-based devices

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MPU Functions for Armv7-M

Functions that relate to the Memory Protection Unit. More...

## Content
| Define values
| Define values for MPU region setup.

## Data Structures
struct | MPU_Type
| Structure type to access the Memory Protection Unit (MPU). More...
struct | ARM_MPU_Region_t
| Setup information of a single MPU Region. More...

## Macros
#define | ARM_MPU_RBAR(Region, BaseAddress)
| MPU Region Base Address Register Value. More...
#define | ARM_MPU_RASR(DisableExec, AccessPermission, TypeExtField, IsShareable, IsCacheable, IsBufferable, SubRegionDisable, Size)
| MPU Region Attribute and Size Register Value. More...
#define | ARM_MPU_RASR_EX(DisableExec, AccessPermission, AccessAttributes, SubRegionDisable, Size)
| MPU Region Attribute and Size Register Value. More...

## Functions
__STATIC_INLINE void | ARM_MPU_Enable (uint32_t MPU_CTRL)
| Enable the memory protection unit (MPU) and. More...
__STATIC_INLINE void | ARM_MPU_Disable ()
__STATIC_INLINE void | ARM_MPU_ClrRegion (uint32_t rnr)
__STATIC_INLINE void | ARM_MPU_SetRegion (uint32_t rbar, uint32_t rasr)
__STATIC_INLINE void | ARM_MPU_SetRegionEx (uint32_t rnr, uint32_t rbar, uint32_t rasr)
__STATIC_INLINE void | ARM_MPU_Load (MPU_Region_t const *table, uint32_t cnt)

## Description

The following functions support the optional Memory Protection Unit (MPU) that is available on the Cortex-M0+, M3, M4 and M7 processor.

The MPU is used to prevent from illegal memory accesses that are typically caused by errors in an application software.

Example:

void main()
{
// Set Region 0
ARM_MPU_SetRegionEx(0UL, 0x08000000UL, MPU_RASR(0UL, ARM_MPU_AP_FULL, 0UL, 0UL, 1UL, 1UL, 0x00UL, ARM_MPU_REGION_SIZE_1MB));
ARM_MPU_Enable(0);
// Execute application code that is access protected by the MPU
ARM_MPU_Disable();
}

## Macro Definition Documentation

#define ARM_MPU_RASR | ( |  | DisableExec,
|  |  | AccessPermission,
|  |  | TypeExtField,
|  |  | IsShareable,
|  |  | IsCacheable,
|  |  | IsBufferable,
|  |  | SubRegionDisable,
|  |  | Size
| ) |  |

This macro is used to construct a valid RASR value. The ENABLE bit of the RASR value is implicitly set to 1.

Parameters

  DisableExec | Instruction access disable bit. 1 = disable instruction fetches.
  AccessPermission | Data access permission configures read/write access for User and Privileged mode. Possible values see ARM_MPU_AP_xxx.
  TypeExtField | Type extension field, allows you to configure memory access type, for example strongly ordered, peripheral.
  IsShareable | 1 = region is shareable between multiple bus masters.
  IsCacheable | 1 = region is cacheable (values may be kept in cache).
  IsBufferable | 1 = region is bufferable (when using write-back caching). Cacheable but non-bufferable regions use write-through policy.
  SubRegionDisable | Sub-region disable field (8 bits).
  Size | Region size with values defined under ARM_MPU_REGION_SIZE_xxx.

#define ARM_MPU_RASR_EX | ( |  | DisableExec,
|  |  | AccessPermission,
|  |  | AccessAttributes,
|  |  | SubRegionDisable,
|  |  | Size
| ) |  |

This macro is used to construct a valid RASR value. The ENABLE bit of the RASR value is implicitly set to 1.

Parameters

  DisableExec | Instruction access disable bit, 1= disable instruction fetches.
  AccessPermission | Data access permission configures read/write access for User and Privileged mode. Possible values see ARM_MPU_AP_xxx.
  AccessAttributes | Memory access attribution, see ARM_MPU_ACCESS_xxx.
  SubRegionDisable | Sub-region disable field (8 bits).
  Size | Region size with values defined under ARM_MPU_REGION_SIZE_xxx.

#define ARM_MPU_RBAR | ( |  | Region,
|  |  | BaseAddress
| ) |  |

This preprocessor function can be used to construct a valid RBAR value. The VALID bit is implicitly set to 1.

Parameters

  Region | The region to be configured, number 0 to 15.
  BaseAddress | The base address for the region.

## Function Documentation

__STATIC_INLINE void ARM_MPU_ClrRegion | ( | uint32_t | rnr | ) |

Clear and disable the given MPU region.

Parameters

  rnr | Region number to be cleared.

__STATIC_INLINE void ARM_MPU_Disable | ( |  | ) |

Disable the MPU.

__STATIC_INLINE void ARM_MPU_Enable | ( | uint32_t | MPU_CTRL | ) |

Parameters

  MPU_CTRL | Additional control settings that configure MPU behaviour

The function ARM_MPU_Enable writes to the register MPU->CTRL and sets bit ENABLE. The parameter MPU_CTRL provides additional bit values (see table below) that configure the MPU behaviour. For processors that implement an MPU Fault Handler the MemoryManagement_IRQn exception is enabled by setting the bit MEMFAULTACT in register SBC->SHCSR.

The following table contains possible values for the parameter MPU_CTRL that set specific bits in register MPU->CTRL.

Bit | MPU_CTRL value | When applied | When not applied
--- | --- | --- | ---
1 | MPU_CTRL_HFNMIENA_Msk | Enable MPU during hard fault, NMI, and FAULTMASK handlers execution | Disable MPU during hard fault, NMI, and FAULTMASK handler execution
2 | MPU_CTRL_PRIVDEFENA_Msk | Enable default memory map as a background region for privileged access | Use only MPU region settings

Example:

// enable MPU with all region definitions. Exceptions are not protected by MPU.
MPU_Enable (0);
// enable MPU with all region definitions and background regions for privileged access. Exceptions are protected by MPU.
MPU_Enable (MPU_CTRL_PRIVDEFENA_Msk | MPU_CTRL_HFNMIENA_Msk);

__STATIC_INLINE void ARM_MPU_Load | ( | MPU_Region_t const * | table,
|  | uint32_t | cnt
| ) |  |

Load the given number of MPU regions from a table.

Parameters

  table | Pointer to the MPU configuration table.
  cnt | Number of regions to be configured.

Note
  only up to 16 regions can be handled as the function ARM_MPU_Load uses the REGION field in MPU->RBAR.

Example:

const ARM_MPU_Region_t mpuTable[3][4] = {
{
{ .RBAR = ARM_MPU_RBAR(0UL, 0x08000000UL), .RASR = ARM_MPU_RASR(0UL, ARM_MPU_AP_FULL, 0UL, 0UL, 1UL, 1UL, 0x00UL, ARM_MPU_REGION_SIZE_1MB) },
{ .RBAR = ARM_MPU_RBAR(1UL, 0x20000000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 0UL, 0UL, 1UL, 1UL, 0x00UL, ARM_MPU_REGION_SIZE_32KB) },
{ .RBAR = ARM_MPU_RBAR(2UL, 0x40020000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 2UL, 0UL, 0UL, 0UL, 0x00UL, ARM_MPU_REGION_SIZE_8KB) },
{ .RBAR = ARM_MPU_RBAR(3UL, 0x40022000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 2UL, 0UL, 0UL, 0UL, 0xC0UL, ARM_MPU_REGION_SIZE_4KB) }
},
{
{ .RBAR = ARM_MPU_RBAR(4UL, 0x08000000UL), .RASR = ARM_MPU_RASR(0UL, ARM_MPU_AP_FULL, 0UL, 0UL, 1UL, 1UL, 0x00UL, ARM_MPU_REGION_SIZE_1MB) },
{ .RBAR = ARM_MPU_RBAR(5UL, 0x20000000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 0UL, 0UL, 1UL, 1UL, 0x00UL, ARM_MPU_REGION_SIZE_32KB) },
{ .RBAR = ARM_MPU_RBAR(6UL, 0x40020000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 2UL, 0UL, 0UL, 0UL, 0x00UL, ARM_MPU_REGION_SIZE_8KB) },
{ .RBAR = ARM_MPU_RBAR(7UL, 0x40022000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 2UL, 0UL, 0UL, 0UL, 0xC0UL, ARM_MPU_REGION_SIZE_4KB) }
},
{
{ .RBAR = ARM_MPU_RBAR(4UL, 0x18000000UL), .RASR = ARM_MPU_RASR(0UL, ARM_MPU_AP_FULL, 0UL, 0UL, 1UL, 1UL, 0x00UL, ARM_MPU_REGION_SIZE_1MB) },
{ .RBAR = ARM_MPU_RBAR(5UL, 0x30000000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 0UL, 0UL, 1UL, 1UL, 0x00UL, ARM_MPU_REGION_SIZE_32KB) },
{ .RBAR = ARM_MPU_RBAR(6UL, 0x50020000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 2UL, 0UL, 0UL, 0UL, 0x00UL, ARM_MPU_REGION_SIZE_8KB) },
{ .RBAR = ARM_MPU_RBAR(7UL, 0x50022000UL), .RASR = ARM_MPU_RASR(1UL, ARM_MPU_AP_FULL, 2UL, 0UL, 0UL, 0UL, 0xC0UL, ARM_MPU_REGION_SIZE_4KB) }
}
};
void UpdateMpu(uint32_t idx)
{
ARM_MPU_Load(mpuTable[idx], 4);
}

__STATIC_INLINE void ARM_MPU_SetRegion | ( | uint32_t | rbar,
|  | uint32_t | rasr
| ) |  |

Configure an MPU region.

The region number should be contained in the rbar value.

Parameters

  rbar | Value for RBAR register.
  rasr | Value for RASR register.

__STATIC_INLINE void ARM_MPU_SetRegionEx | ( | uint32_t | rnr,
|  | uint32_t | rbar,
|  | uint32_t | rasr
| ) |  |

Configure the given MPU region.

Parameters

  rnr | Region number to be configured.
  rbar | Value for RBAR register.
  rasr | Value for RASR register.