JPS6426268A - Priority control system in main storage access - Google Patents

Abstract

PURPOSE:To simplify a circuit and to reduce hardware quantity by observing the new relation and the old relation between plural ports, selecting one of the access requests of the old one, thereafter, determining priority based on the condition of a unit. CONSTITUTION:A main storage access from the plural units is held by plural ports 30 provided in correspondence to the respective units and thereafter, the priority between the respective ports 30 is determined. In order to permit an access to the main storage, the relation of new one and old one between the ports 30 is discriminated and a means 32 is provided to select the old one. A main storage access request, which is selected between the respective ports 30 of the respective units is sent to a priority determining circuit 33 and so that an access order can be determined to the main storage memory. Thus, a control circuit between ports 30 in correspondence to the respective units and a priority determining circuit are respectively simplified and the hardware quantity is reduced as a whole. Then, the whole of a priority determining circuit block is easily divided into a logic circuit suitable for highly integration.