| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem of conventional memory access devices of stopping of processing of CPUs since while one of the CPUs makes access to a shared memory, the other CPU continues reading an exclusive control flag and exclusively possesses a bus. SOLUTION: The device is provided with a residual capacity counter 6 indicating residual capacity of quantity of data read and written by a CPU 2a using a memory 3 in addition to an exclusive control flag 5 to which a value indicating usage of the memory 3 is written by one of the CPUs, and it determines whether or not the residual capacity counter 6 indicates zero by a zero comparison circuit 7 and makes the exclusive control flag 5 zero. The other CPU 2b not using the memory 3 refers to the residual capacity counter 6, and after the passage of a time period corresponding to residual capacity of the residual capacity counter 6, it reads out the exclusive control flag 5 and determines propriety of usage of the memory 3. COPYRIGHT: (C)2004,JPO
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