| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a DMA controller capable of grasping the use ratio of a bus or access situation by plural devices without any complicated control and controlling an operating mode for every block of a memory in accordance therewith. SOLUTION: On the basis of an address signal ADD, a bus occupancy ratio S of a bus 5 is calculated by a bus monitor part 8. Besides, the operating situations of respective DMA control parts 1-3 are detected by the bus monitor part 8. On the basis of the bus occupancy ratio S and the operating conditions of the respective DMA control parts, the operating modes of respective memory blocks 71-74 provided in a memory 7 are respectively controlled by a memory controller part 9. Namely, the memory block, which does not require high speed processing, is operated in a power down mode or self-refresh mode. Therefore, power consumption can be effectively suppressed low.</p> |
