CPU 电源状态程度越深，采取的电能节省措施就越多 — 比如说停止处理器时钟或停止外部中断请求。

The deeper the C state, the more power saving steps are taken—steps like stopping the processor clock or stopping interrupts from coming in.

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DMA可以被外部(INT3 - 0)、内部的(片内定时器和串口)中断触发运行，传输完成后可以向CPU发出中断请求。

DMA can run constantly or can be triggered by exterior interruption (INT3-0), interior interruption (timer and serial port), at the end of transfers, send interruption signal to CPU.

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