Synchronizing slave processors through eavesdrop by one on periodic

Abstract

Data bases of a first and second input output processor (IOP), which are primary and secondary slave IOPs, respectively, are synchronized, and communications by a master controller is made only to the first IOP. Each IOP is executing the same tasks utilizing their own clocking systems. A method for periodically verifying that the first and second data base remain synchronized comprises the steps of sending a sync-verify type message to the first IOP. The second IOP eavesdrops on the communications, and when the second IOP recognizes that the message is addressed to the corresponding primary slave IOP, accepts the message. Upon detecting the message is of the sync-verify type by each IOP, operations by each IOP are suspended. A number is generated by each IOP of its own data base, the number being indicative of the contents of the information stored in the data base. A status request type message is issued by the master controller to the first IOP for the number generated by the first IOP, and a status request type message is issued by the master controller to the second IOP for the number generated by the second IOP. Upon receipt of the numbers by the master controller, the value of the number generated by the first IOP is compared to the value of the number generated by the second IOP, thereby determining that the information stored in the first and second data bases are the same when the numbers compare.