| 摘要 |
PURPOSE:To shorten a bus access time in case of using a bus of a lowest-order priority device, by constituting so that a use permission signal to the lowest-order priority device can be received directly by a bus controller. CONSTITUTION:When there is no bus using request from high-order priority device groups 200-400, and there is only a bus using request from a lowest-order priority device 100, a bus controller 500 generates a bus using inhibition synchronizing signal to a signal line 16. In this case, the device 500 sends out a bus using permission signal through a signal line 14 to the device 100, and does not send it out to the devices 200-400. However, in case when a bus using request has been sent out from the devices 200-400 during a deciding time which has been prescribed in advance, after the bus using inhibition synchronizing signal has been sent out; priority is decided during said deciding time, and after a prescribed time, the bus using permission signal is sent out through the signal line 14. In this way, a use permission signal to the device 100 is received directly, the bus access time is shortened. |
