Patent ID: 6061601
Filing Date: 2000-05-09
Classification: G06F

Abstract:
A tandemized data processing system comprising a first and a second programmed logic controller and centralized governance means alternatively governing one controller in a master state, whilst allowing the other controller in standby state, each controller being provided with a local powering facility and a local bus, and each local bus being attached via a respective bus interface element to a general bus provided with input/output subsystems, characterized in that the system furthermore has a high-speed serial link between the first and second controller for communicating status signalizations from the master controller to the other controller, at least one of said buses being provided with local communication facilities for therewith consistently enabling operator interaction with any controller that is actually in said master state, said centralized governance means comprising a guard circuit, said guard circuit configured to have a first state and a second state wherein a respective one of said controllers is a master and said other controller is in standby, and a third state and a fourth state for blocking master operation of said first and second controller, respectively.