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微型计算机内存与外设之间的数据传送一般有两种方式:(1)编程方式(包括程序中断):在程序控制下,数据中经CPU的累加器(或寄存器),每次传送一个字;当传送一个以上字时需要变址;故速度受到解释指令和变址计算时间所限制。(2)DMA方式:DMAC控制取代了CPU控制,内存直接和外设交换信息,地址由DMAC给出,故速度快。 APPLEⅡ目前在国内外应用很广,但有关DMA技术在其上的应用,尚未见于文献报导。虽然APPLEⅡ为此设计了接口信号,然因6502 CPU芯片本身不能很好适合DMA操作,故没有与之专门匹配的
Microcomputer memory and peripheral data transfer between the general two ways: (1) programming methods (including program interruption): under program control, the data in the CPU by the accumulator (or register), each transmission of a word ; Indexing is required when more than one word is transferred; therefore, speed is limited by interpreting instructions and indexing time. (2) DMA mode: DMAC control to replace the CPU control, memory and peripherals to exchange information directly, the address given by the DMAC, it is fast. APPLE Ⅱ is widely used at home and abroad at present, but the application of DMA technology has not been found in the literature. Although APPLE Ⅱ designed for this interface signal, then because of the 6502 CPU chip itself is not well suited for DMA operation, it does not specifically match