| 摘要 |
When a unit connected to a data transfer bus on which data transfer is controlled synchronously with a bus cycle makes a request for using the bus, permission is granted to one of the units which have made the request. The permission to use the bus is switched over at a bus cycle when data transfer is completed in the unit. Consequently, the bus cycle can be shortened, and the speed of the data transfer by the bus can be increased. To achieve this, the unit which has granted permission to use the bus sends out a notifying signal notifying switch over of the permission to use the bus at a bus cycle, which precedes the bus cycle when data transfer is completed. The permission to use the bus granted to the unit, which has completed data transfer, is cancelled on the basis of the notifying signal at the bus cycle when data transfer is completed. Permission to use the bus is granted to a subsequent unit at that bus cycle when there is the subsequent unit which is requested use of the bus.
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