| 摘要 |
A microcomputer device contains a CPU with an arithmetic/logic unit and data/address registers on a single semiconductor integrated circuit having on-chip macrocode and microcode storage. A macrocode word is fetched from an on-chip ROM and stored in an instruction register in the CPU, then a sequence of microcode words is fetched from microcode store based on this macrocode word. In some machines, microcode for two states is fetched at one time, and then applied to the ALU register and bus controls in the next two successive cycles. In this manner, the microcode store can be the same as macrocode store.
|
