论文部分内容阅读
在一个典型的具有３级总线结构的ＰＣ机里，一方面各级总线上的主设备都可面对自己的地址空间启动各自总线上的访问周期，另一方面系统中各类地址空间实体分布在各级总线上，使得各级总线主设备的访问地址与各处实际空间的映射关系千头万绪．该文把物理上分布于各处的地址空间组织成一个整体，并视之为一个独立于各级总线主设备地址空间之外的、又为各级主设备所共有的空间（系统空间），然后在此基础上着重分析了两级总线桥如何共同把各级总线主设备对自己地址空间的访问映射于这个系统空间中，站在系统的高度理清这千头万绪的映射关系．
In a typical PC with a 3-level bus architecture, on the one hand all the main bus devices on the bus can address their own address space to start their visit on the bus cycle, on the other hand the system of various types of address space entity distribution At all levels of the bus, making all levels of bus master access address and the actual space around the mapping of a multitude of things. This paper organizes the address space which is physically distributed everywhere into a whole and treats it as a space (system space) that is independent of the bus master address space at all levels and is also shared by the master devices at all levels. Then on this basis, it emphatically analyzes how the two-level bus bridge can map the access of all levels of bus masters to their own address space in this system space, and at the height of the system, sort out the multitude of mapping relationships.