stm32 ccmram的使用(stm32f407)

写在前面

今天在搞STM32F4时，用到了一部分特殊内存——CCM。搜了搜网上没多少介绍，索性自己查手册。
某些芯片没有CCM

基本架构

废话少说，先看看这块内存特殊在哪里。官方的基本架构说明如下：
  The main system consists of 32-bit multilayer AHB bus matrix that interconnects:

Eight masters:
– Cortex® -M4 with FPU core I-bus, D-bus and S-bus
– DMA1 memory bus
– DMA2 memory bus
– DMA2 peripheral bus
– Ethernet DMA bus
– USB OTG HS DMA bus
Seven slaves:
– Internal Flash memory ICode bus
– Internal Flash memory DCode bus
– Main internal SRAM1 (112 KB)
– Auxiliary internal SRAM2 (16 KB)
– AHB1 peripherals including AHB to APB bridges and APB peripherals
– AHB2 peripherals
– FSMC
  The bus matrix provides access from a master to a slave, enabling concurrent access and efficient operation even when several high-speed peripherals work simultaneously. The 64-Kbyte CCM (core coupled memory) data RAM is not part of the bus matrix and can be accessed only through the CPU. This architecture is shown in

其架构和之前的STM32F1x区别还是挺大的。由上可知，CCM共64KB，是直接挂在D-bus上的，除了CPU（即Cortex-M核）之外，谁都无法访问。