Patent ID: 6411857
Filing Date: 2002-06-25
Classification: G05B,G06F

Abstract:
A secondary industrial controller providing redundancy with a primary industrial controller executing a user program to control an industrial process, the secondary industrial controller comprising:(a) an electronic memory holding: (i) a copy of the user program describing the control of the process; (ii) a secondary I/O data table holding output values changed by the user program; (iii) a quarantine I/O data table; (b) a processor communicating with the electronic memory and operating to: (i) receive transmission of output values from a primary industrial controller; at the end of execution of the user program by the primary industrial controller to the quarantine I/O data table; of the secondary industrial controller (ii) only after completion of the transmission of the output values into the quarantine I/O data table, transferring the output values from the quarantine I/O data table to the secondary I/O data table; and (iii) at a switch-over time, executing the copy of the user program to modify the output values in the secondary I/O data table and to transmit the output values from the secondary I/O data table to the industrial process wherein the electronic memory holds at least two user programs and wherein the secondary industrial controller receives identification of one current user program of the two programs from the primary industrial controller, and wherein, â€ƒat switch-over time, the processor executes the one user current program.