| 摘要 |
PURPOSE:To realize a cyclic control which is abundant in flexibility, by means of a simple constitution, by using two read-only memories and a register, in a microprogram control system which has used a vertical microinstruction. CONSTITUTION:When a microinstruction A is read out from a microprogram memory, a control signal required for executing the first machine state A0 is read out from a decode ROM23, and simultaneously a state of the next machine state is read out from a control ROM21. An output of the control ROM21 is latched to a state register 22 by the next machine clock, its output and a command part of the microinstruction A are made an address, and a control signal required for executing a machine state A1 is read out. At the same time, the control ROM21 is read out, and it is decided that the next machine state is the first machine state of an execution cycle of the next microinstruction. Accordingly, the state register 22 is cleared by the next machine clock. In the same way, microinstructions B, C, D are executed. |
