| 摘要 |
PURPOSE:To prevent the delay of memory cycle and at the same time to realize a long-time initialize from outside, by subjecting a refresh control circuit to a DMA function and also synchronizing the external clear signal. CONSTITUTION:An access is given to a memory 22 according to the MEMSTART sent from a CPU21 based on the DMAREQ sent from a DMA device 23. At the same time, a control part A24 that forms a refresh control circuit is also started. The DMA device 23 according to a refresh clock is subjected to an apparent functional operation via a refresh counter of the part A24, therefore the memory 22 is refreshed by the REFMODE without competing against the MEMSTART. Accordingly, a racing circuit can be eliminated to prevent the delay of the memory cycle. On the other hand, the external CLEAR signal is synchronized with the refresh clock through a control part B25 to clear the CPU21. Thus the refresh is carried out writhout fail. |
