KEIL开发的基于STM32F407外部扩展内存的实例。外部扩展2M的SRAM，实现了读写功能。代码由微雪开发板测试通过-KEIL development Based on STM32F407 external expansion memory instance. External expansion 2M of SRAM, the read and write capabilities. By the test code by Flurries development board