| 摘要 |
PURPOSE:To improve the efficiency of the titled system in terms of task control by using a stored and held flag to decide whether or not a memory shared by plural arithmetic units is under an access mode and controlling the access of each arithmetic unit. CONSTITUTION:Flip-flops F/F1 and F/F2 of a logical circuit 5 store and hold the flags of arithmetic units CPU1 and CPU2 which give access to an external memory RAM. While an AND gate G is closed when the F/F1 is set and inhibits reading of a flag given from the CPU2 having a lower priority. Therefore the access given from CPU1 and CPU2 is accepted in the prescribed priority order. The CPU2 can know that the memory RAM is receiving an access through a data bus 32 as long as the F/F2 is kept under a reset state. |
