| 摘要 |
PURPOSE:To arbitrarily change the priority level of each device by providing a memory, which outputs a permission signal based on the state of the request signal of the device and the state of the preceding permission signal, and a holding means which holds the permission signal from the memory and outputs it to the memory at the next time. CONSTITUTION:A memory 11 which outputs the permission signal based on the request state of the device and the state of the preceding permission signal and a holding means 12 which holds the output of the memory 11 and outputs it to the memory 11 at the next time are provided. Since the priority level of the device is stored in the memory 11, it is unnecessary to extend the hardware constitution in case of the increase of the number of devices, whose priority levels should be controlled, if the setting information volume of priority level is equal to or smaller than the capacity of the memory 11. If contents of the memory 11 are so set that continuous designation of the same device is inhibited, processings of devices having lower priority levels are prevented from being stagnated by monopolization of the device having a higher priority level; and in case of the change of priority levels of devices, it is sufficient if a memory having different contents is attached.
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