A bus control system in which priority for the use of a bus is set in the order of an I/O device, a hardware operation unit and a data processing unit so that the use of the bus by the data processing unit is suppressed during the continuous processing operation of the hardware operation unit in order...http://www.google.com.hk/patents/US4583160?utm_source=gb-gplus-share專利 US4583160 - Priority control apparatus for a bus in a bus control system having input/output devices
