DMA控制器技术

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<>如图是DMA控制器硬件结构示意图。                                                         </P>
<DIV class=O v:shape="_x0000_s1026">
<DIV>　　<B>DMA</B><B>的可能引脚说明：</B> </DIV>
<DIV>　　数据总线：用于传送数据。 </DIV>
<DIV>　　地址总线：用于选择存储器地址。 </DIV>　　数据传送信号：MEMR为存储器读操作信号，MEMW为存储器写操作信号，IOR为外设读操作信号，IOW为外设写操作信号。
<DIV>　　DRQ：DMA请求信号。是外设向DMA控制器提出要求DMA操作的申请信号。 </DIV>　　DACK：DMA响应信号。是DMA控制器向提出DMA请求的外设表示已收到请求和正进行处理的信号。
<DIV>　　HOLD：总线请求信号。是DMA控制器向CPU要求让出总线的请求信号。 </DIV>
<DIV>　　HLDA：总线响应信号，是CPU向DMA控制器表示允许总线请求的应答信号。 </DIV>
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