In a bus system, in accordance with reservations of transfers of isochronous blocks of data and with requests by the node devices for transfers of ones of the isochronous blocks of data and regular blocks of data, a bus manager generates a schedule of the operating rate of a bus channel, the frequency of assignment of the bus channel, and the size of a continuously transferred piece of data on the bus channel for each of the blocks of data, so that the piece of data is transferred at the operating rate of the bus channel as low as possible in each transfer cycle. The bus manager determines assignment of the bus channel to the blocks of data in accordance with the schedule and with the requests for transfers of the blocks of data. The bus manager provides information on the operating rate of the bus channel for each block of data and issues a grant of the bus channel, during a period of time determined in accordance with the size of the continuously transferred piece of data for that block of data and with the operating rate of the bus channel for that block of data, via the bus control line to the node device. In response to a grant of the bus channel for that block of data, the node device transfers the piece of data of that block of data to another node device at the operating rate of the bus channel contained in the information received by the node device, during the period of time of the grant of the bus channel. In the bus system, power consumption is reduced.