| 摘要 |
PURPOSE:To simplify the constitution of a DMA control circuit by outputting a DMA permission signal corresponding to a DMA permission address signal in accordance with the DMA permission signal outputted from a CPU and permitting a DMA. CONSTITUTION:When no input of a DMA request signal is given onto signal lines 1-1-1-7, the contents of a ROM 2 for control of DMA request are set in a state where an access is given to a DMA request waiting mode. Thus no information is outputted to a DMA request signal line 3 and a DMA permission address signal line 4. When the DMA request signals are inputted from lines 1-1-1-7, the contents of the ROM 2 are shifted to a state where an access is given to an output address of each DMA request address. Then the DMA request signal set on the line 3 is outputted onto the line 4 together with the DMA permission address signal corresponding to the DMA request signals inputted from lines 1-1-1-7. Thus the DMA request address receives an access. |
