| 摘要 |
PROBLEM TO BE SOLVED: To provide an access arbitrating circuit capable of efficiently using a memory bus by preventing the occurrence of overrun to disable the guarantee of normal print data. SOLUTION: This circuit 115 has a counter 101, a select part (selector) and arbitrating parts 102 to 114 and corresponding to which external memory is accessed by a CPU for the request of the CPU or corresponding to the respective CPU requests divided by a transfer code outputted by the CPU, the order of priority is applied to the simultaneously inputted requests of DMA. The counter 101 performs count-up for '1' every time corresponding to the last signal of each of access and when a specified value is reached, plural kinds of priority signals are generated. On the basis of the priority signal selected for each CPU request, the arbitrating parts 102 to 114 perform operation for passing one of the simultaneously inputted requests of the CPU and the DMA and masking the other request.
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