DSIH70 自动化卡件模块
模式寄存器
直接内存访问和Intel 8237 DMAC Er。Nikhil Marriwala数据传输方案 编程I/O 同步I/O 异步I/O 中断驱动I/O 直接存储器存取（DMA）为什么DMA应用于DMA DRAM刷新 视频显示屏刷新 批量数据传输 I/O设备到内存&内存到I/O装置传输 Intel 8237 DMAC的存储器到存储器数据传输功能 启用/禁用单个DMA请求的控制 四个独立DMA信道 所有通道的独立自动初始化 内存到内存传输 内存块初始化 地址递增或递减 高性能：使用Intel 8237 DMAC的5 MHz 8237A-5功能，每秒传输敢达1.6M字节 可直接扩展到任意数量的通道 终止传输的进程结束输入 软件DMA请求 DREQ和DACK信号的独立极性控制 有EXPRESS–标准温度范围 提供40引脚Cerdip和塑料封装PIN图Intel 8237 Intel 8237框图进程结束：I/O内部寄存器8237系统接口 在模式寄存器中写入一个控制字，用于选择信道，并指定读取、写入或验证传输类型和DMA模式（块、单字节等） 在命令寄存器中写入一个控制字，指定四个通道之间的优先级等参数
Mode register
Direct Memory Access & Intel 8237 DMAC Er. Nikhil Marriwala Data Transfer Schemes Programmed I/O Synchronous I/O Asynchronous I/O Interrupt driven I/O Direct Memory Access (DMA) Why DMA Applications of DMA DRAM Refreshing Video Display Screen Refreshing Bulk data Transfer I/O DEVICES TO MEMORY & MEMORY TO I/O DEVICES TRANSFER MEMORY TO MEMORY DATA TRANSFER Features of Intel 8237 DMAC Enable/Disable Control of Individual DMA Requests Four Independent DMA Channels Independent Autoinitialization of All Channels Memory-to-Memory Transfers Memory Block Initialization Address Increment or Decrement High Performance: Transfers up to 1.6M Bytes/Second with 5 MHz 8237A-5 Features of Intel 8237 DMAC Directly Expandable to Any Number of Channels End of Process Input for Terminating Transfers Software DMA Requests Independent Polarity Control for DREQ and DACK Signals Available in EXPRESS –Standard Temperature Range Available in 40-Lead Cerdip and Plastic Packages PIN Diagram Intel 8237 Block Diagram of Intel 8237 END OF PROCESS: I/O Internal Registers 8237 System Interface Write a control word in the mode register that select the channel and specify the type of transfer read,write or verify and the DMA mode (block, single byte etc.) Write a control word in the command register that specifies parameters such as priority among four Channels
