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程序查询方式

程序中断方式

DMA方式

计组- I/O控制方式之DMA方式

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⚠️ CPU 和 DMA 同时要求使用存储器总线时，DMA 请求优先级更高

因为 DMA 请求得不到及时响应，I/O 传输数据可能会丢失。

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