配置需要Device 或 Strongly order执行外设
== 引用硬汉嵌入式老哥的教程。==
配置参数可看我另一篇文章。
读写Cache都是关闭的,比如FMC外设驱动,扩展IO,LCD,NOR FLASH SRAM,ETH收发描述符空间
特点:保证严格按照程序代码执行
缺点:不支持非对齐访问
配置 FMC 扩展 IO 的 MPU 属性为 Device 或者 Strongly Ordered
c
/* 配置 FMC 扩展 IO 的 MPU 属性为 Device 或者 Strongly Ordered */
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.BaseAddress = 0x60000000;
MPU_InitStruct.Size = ARM_MPU_REGION_SIZE_64KB;
MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
MPU_InitStruct.IsBufferable = MPU_ACCESS_BUFFERABLE;
MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_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;
以太网收发描述符空间MPU配置
c
/* 配置以太网收发描述符部分为 Device */
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.BaseAddress = 0x30040000;
MPU_InitStruct.Size = MPU_REGION_SIZE_256B;
MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
MPU_InitStruct.IsBufferable = MPU_ACCESS_BUFFERABLE;
MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
MPU_InitStruct.Number = MPU_REGION_NUMBER2;
MPU_InitStruct.SubRegionDisable = 0x0;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;
配置为最低性能NORMAL,关闭读写Cache
特点:可以像F1、F4那样使用内部SRAM。适合初学者
缺点:性能差
c
/* 配置 AXI SRAM 的 MPU 属性为 Write back, Read allocate, Write allocate */
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.BaseAddress = 0x24000000;
MPU_InitStruct.Size = MPU_REGION_SIZE_512KB;
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_NUMBER0;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL1;
MPU_InitStruct.SubRegionDisable = 0x00;
MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;
配置为NORMAL,此时关闭写Cache,开启读Cache(透写)
特点:SDRAM 做LCD显存和动态内存下非常方便,保证数据是直接写到显存的,开启读Cache,SDRAM 的读性能提升一倍,提升GUI性能(如LTDC)。
缺点:由于开启了读Cache,用户需要调用SCB_CleanInvalidateDCache()函数管理数据一致性问题。只有多主控操作此空间才需要处理
c
/* 配置SDRAM的MPU属性为Write through, read allocate,no write allocate */
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.BaseAddress = 0xC0000000;
MPU_InitStruct.Size = MPU_REGION_SIZE_32MB;
MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;
MPU_InitStruct.IsCacheable = MPU_ACCESS_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;
配置为NORMAL 读写Cache全开,最强性能
特点:性能最强
缺点:由于读写Cache全开,用户需要调用SCB_CleanInvalidateDCache()函数管理数据一致性问题。只有多主控操作此空间才需要处理
c
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.BaseAddress = 0x24000000;
MPU_InitStruct.Size = MPU_REGION_SIZE_512KB;
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_NUMBER0;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL1;
MPU_InitStruct.SubRegionDisable = 0x00;
MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;