Abstract: A bus system for an information processing system in which data transfer among plurality of modules is controlled on a common bus. In response to a bus use request from a module, a command is issued for aborting data transfer being performed by another module having a lower priority. The module which is transferring the data responds to the abort command by issuing a signal indicating that a word being transferred is the final word. The data is transferred between a master and a slave through an address bus having a same width as the data in synchronism with a clock supplied from a bus controller.

Abstract: A plurality of process requests generated from processing units, for example, direct memory access (DMA) channels are controlled by a preference circuit in accordance with a priority level assigned to each of the processing unit. An information of the highest priority obtained processing unit and its priority level is stored in latches. Another process requests having the same priority level as the stored processing unit are inhibited from being supplied to the preference circuit, so that the first generated process request is accepted and executed prior to acceptance of the another process requests having the same priority level.

Abstract: An address bus control apparatus links a memory bus connected with a CPU and a memory unit and a system bus connected with input/output units. The address bus width of the system bus is smaller than that of the memory bus and one of the input/output units is a master unit using address data of a smaller width than the address bus width of the system bus for accessing another unit. The address bus control apparatus, when bus identifying information from a master unit identifies the memory bus, delivers first complementary address data together with address data from the master unit onto the memory bus and, when the bus identifying information identifies the system bus, delivers second complementary address data onto the system bus, and thereby secures necessary address data width for each bus.

Abstract: A bus master and a plurality of bus slaves are connected through a data bus and a control bus, and data transfer of hand shake system is performed. In the control bus, at least data strobe signal from the bus master to the bus slave and data confirmation signal from the bus slave to the bus master are transmitted. The data strobe signal from the bus master is one inputted to a bus strobe control circuit. The data confirmation signal from the bus slave is also inputted to the bus strobe control circuit, and the control circuit supervises level of the data confirmation signal being asserted and confirms negation, and then asserts the data strobe signal to the bus slave. Thereafter, a next data transfer is started.