针对STM32F7系列平台的MPU，Cache特性，需要注意哪些问题？

发布于 2017-05-08 11:59:58 浏览：6702 订阅该版

17 个回答

softwind 2017-05-08

这家伙很懒，什么也没写！

还有就是F7的BSP中，关于MPU的部分，

```
  /* Configure the MPU attributes as WB for SDRAM */
  MPU_InitStruct.Enable = MPU_REGION_ENABLE;
  MPU_InitStruct.BaseAddress = 0xC0000000;
  MPU_InitStruct.Size = MPU_REGION_SIZE_8MB;
  MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_BUFFERABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_CACHEABLE;
  MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;
  MPU_InitStruct.Number = MPU_REGION_NUMBER1;
  MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
  MPU_InitStruct.SubRegionDisable = 0x00;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;

HAL_MPU_ConfigRegion(&MPU_InitStruct);

/* Configure the MPU attributes as none-cache for 1MB SDRAM */
  MPU_InitStruct.Enable = MPU_REGION_ENABLE;
  MPU_InitStruct.BaseAddress = 0xC0100000;
  MPU_InitStruct.Size = MPU_REGION_SIZE_1MB;
  MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
  MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;
  MPU_InitStruct.Number = MPU_REGION_NUMBER2;
  MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
  MPU_InitStruct.SubRegionDisable = 0x00;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;

HAL_MPU_ConfigRegion(&MPU_InitStruct)
```

然后系统的Heap是这样定义的：

```
#ifdef RT_USING_EXT_SDRAM
    rt_system_heap_init((void*)EXT_SDRAM_BEGIN, (void*)EXT_SDRAM_END);
    sram_init();
#else
    rt_system_heap_init((void*)HEAP_BEGIN, (void*)HEAP_END);
#endif
```

也就是说把整个的外部SDRAM作为System Heap；但SDRAM又定义了两个具有不同的MPU属性Region，而且是Overlapped的，这是出于什么样的考虑？