| 摘要 |
PURPOSE:To continue processing without causing the shutdown of a system, by performing degenerated operation even if an instruction look-ahead control circuit becomes abnormal, by providing a control fault detecting circuit and instruction look-ahead inhibiting circuit for instruction look-ahead control. CONSTITUTION:If instruction look-ahead control circuit 12 will not operate normally owing to a fault, control fault detecting circuit 13 detects the fault of circuit 12 and sets instruction look-ahead inhibiting FF14. Once FF14 is set, circuit 12 stops instruction look-ahead operation and access control part 11 starts instruction fetching access to storage device 1 instead of fetching the contents of instruction buffer register 4 into instruction execution control part 2, thereby reading the next instruction out of device 1. The next instruction read out of device 1 is inputted directly to control part 2 without being set in register 4. Thus, if a fault occurs in circuit 12, the fetching of instructions and the execution of the instructions are performed by control part 2 in series and consequently although the performance deteriorates, the processing is carried out without the shutdown of the system. |
