7、间接阶段7.1 间接阶段的微程序由6.1节明白了间接地址的性质及其访问方法,下面来了解这在实际计算机里是怎样被控制的。间接地址的处理过程叫做间接阶段。如图6-2或图6-3所示,间接访问同直接访问的区别取决于访存指令码的第15位是“0”还是“1”。因此,在取指令阶段,从主存贮器取到Ⅰ寄存器中的指令是访存指令,且其第15位是“1”时进入间接阶段。将间接阶段微程序用ROM地址14_8、15_8,和16_8的微指令表示如图7-1。取指令阶段的微程序是把P寄存器所示主存贮器地址的内容送入Ⅰ寄存器,把对应于 Indirect Phase 7.1 Indirect Phase Microprocesses Section 6.1 understands the nature of the indirect address and how to access it. Let’s see how this is controlled in the actual computer. Indirect address processing is called an indirect phase. As shown in Figure 6-2 or Figure 6-3, the difference between indirect access and direct access depends on whether bit 15 of the fetch instruction is “0” or “1”. Therefore, during the fetch phase, the instruction fetched from main memory to the I register is a Fetch Instruction and the 15th bit is “1” into the indirect phase. The indirect stage microprogram is shown in Figure 7-1 using microinstructions of ROM addresses 14_8, 15_8, and 16_8. The fetch phase of the microprogram is the P register shown in the main memory address into the I register, the corresponding