标题DMA方式——DMA Mode

　　DMA is the short for "direct memory access".DMA is a data transmission mode more efficient than interrupt mode. In such a mode，interfaces could intercommunicate data with memory directly，when DMA controller has taken over bus control from CPU.Therefore，blocks of data could be transmitted more rapidly，what's more important，CPU needn't refresh its registers and continues executing its interior task，which would sharply promote the system performance.
　　DMA是“直接内存访问”的缩写，它是一种比中断方式更有效的数据传送模式。在DMA方式下，当DMA控制器从CPU取得了总线控制权后，接口便可与内存之间直接进行数据交换(不经过CPU)。因此，成块的数据可很快地传输，并且更为重要的是，CPU本身不用刷新其内部寄存器的内容，从而继续处理其内部工作，这样，系统性能将得到明显的提高。