扩展MCU功能时，明智地使用外部存储器接口

　　扩展MCU功能时，明智地使用外部存储器接口

　　单片机在许多嵌入式系统设计的关键要素，但往往附加功能都需要实现必要功能。在基于MCU的设计中，最受限制的因素之一是片上存储器。越来越多的应用需要更多的系统内存比MCU有。特别是，先进的人机界面（HMI）的设计需要一个显着量的只读图像和音频信息不容易存储在MCU片上闪存。此外，越来越多的应用程序发现片上RAM过于限制的先进通信信道，需要显着的数据缓冲和存储。

　　本文将回顾一些可用的外部存储器接口对现代微控制器。这将帮助设计师更有效地实现基于单片机的系统需要额外的外部存储为NVM的闪光或挥发性SRAM / DRAM。

　　External memory interfaces to SDRAM

　　Perhaps the most obvious external memory interface needed to extend storage capability is for large working SRAM. Typically， MCUs have a relatively small amount of on-chip SRAM and often an application will require more working memory than is available on-chip. Advanced user interfaces， for example， may require a significant amount of buffer memory for processing graphical user interfaces （GUIs） and creating video or audio prompts. Often， compression techniques are used when these data files are stored or transmitted to reduce local storage requirements or system bandwidth requirements. This means that a significant amount of working storage may be needed to decompress these files. Often， too， large working memories are needed in communications application or in digital-signal processing applications as buffer storage.