Duplex computer system

摘要

Herein disclosed is a duplex computer system to be used in process automations or factory automations. The system is constructed of two computer (or processor) systems connected with a common backplane bus and a plurality of I/O units to be controlled by those computer systems. Each of these systems is composed of a CPU having a self-diagnosis function for outputting a ready signal indicating whether or not its operations can be normally accomplished, a communication interface unit for interfacing with the backplane bus, and a duplex control unit that receives the ready signal output from the CPU in order to determine which of the computer systems is to be brought into a control status while the other is brought into a standby status. Thus, it is possible to provide a highly reliable system, in which the duplex control can be accomplished without providing an independent duplex control unit between the two computer systems, and in which trouble experienced by one computer system will not exert any influence upon the operations of the other computer system.