| 摘要 |
PROBLEM TO BE SOLVED: To provide a DMA controller by which access to a shared bus by a CPU is secured by detecting an operating state of a device and changing the contents of mediation control of a bus according to its detected result. SOLUTION: The operating states of DMA control parts 1 to 3 are detected based on DMA processing signals dma 1 to 3 by a device monitoring part 208 in this DMA controller. And a priority order table is selected by a priority order table selecting part 218 according to the detected results of the device monitoring part 208. Thus, the mediation control of the bus is performed according to the priority order table according to the operating states of the DMA control parts 1 to 3 at a bus mediating part 206. Thereby, exclusive holding of the bus 5 by the DMA control part 1 to 3 is prevented and required access time is secured for the CPU 14 as well.
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