| 摘要 |
PURPOSE:To eliminate the need for processing such as save or recovery of content of an address register by disregarding the external access request until a central processing unit starts once the accessing to a main storage device and completes accessing. CONSTITUTION:When the central processing unit 1 starts a memory access routine, and whether the start cause to the routine is based on the internal access request or on the external access request is discriminated. When the cause is based on the internal access request, an external access request which might be caused successively is masked and after a prescribed memory address is set from one of registers to an address register 1a succeedingly, the access to a main storage device 2 is performed. When the central processing unit 1 completes the memory access, after the masking to the interruption based on the external access request is released, the memory access routine is finished.
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