| 摘要 |
PURPOSE:To prevent competition between direct memory access control and refresh control, by controlling the refresh operation of dynamic type memory independently from the direct memory access control. CONSTITUTION:When direct memory access request DMA is produced, the refresh operation preparating signal RRD earlier in timing than the refresh start signal RFS is produced from the refresh counter RFC. Further, when the direct memory access request signal DMA is produced, the refresh operation preparation signal RRD is produced in advance, and if the refresh start signal RFS is not produced, the direct memory access request is kept waited for some time. Thus, since the competition between the refresh operation and the direct memory access operation can be prevented, the data in memories can not improperly be converted or refreshed, allowing to increase the reliability. |
