| 摘要 |
PURPOSE:To improve the use efficiency of a common bus, by providing a request signal line independently of the common bus and transmitting a bus use request to this signal line in the system where plural data transfer devices are connected to one common bus to transfer data. CONSTITUTION:Plural data transfer devices DT are connected to a common bus 3 and a request (REQ) signal line 4. A data control part 1 of each device DT reports a data transmission request signal to an REQ transmitting part 10 when a data transmission request is generated, and the transmitting part 10 receives this signal to transmit an REQ signal to the signal line 4 after confirming that the signal line 4 is not used in a use state detecting part 14. If a collision is detected during the transmisson of the REQ signal by a collision detecting part 13, the transmission of the REQ signal is stopped, and the REQ signal is transmitted again after an optional time. In the receiving size, the REQ signal is detected and analyzed in an REQ analyzing part 11, and a normal signal is written in an FIFO queue 12. When the bus 3 becomes idle, the control part 1 reads out the REQ signal from the queue 12 to transmit data to the bus 3. |
