Voter logic block including operational and maintenance overrides in a process control system

Abstract

A voter function block, which can be integrated into a function block diagram programming environment in a process plant control or safety system, implements voter logic in conjunction with providing operational and maintenance overrides which may be set to override individual inputs to the voter function block as well as to override the output of the voter function block. The voter function block, which is easy to create, use, test, debug and document, includes one or input limit detection units which detect if a particular redundant input has reached a specified limit indicating a condition within the process plant, an override unit that may be set by a user to override the consideration of that input in the voting function, a voting logic entity that determines if a trip condition exists based on the values of the valid or non-inhibited inputs, and an inhibit block that may used to override the output of the voter logic block during, for example, a startup or other operational condition. The voter function block may be integrated into a process control or safety system by being communicatively connected to other function blocks, such as to analog or digital input function blocks, analog or digital output function blocks, control function blocks, cause and effect function blocks which implement cause and effect logic, etc. Within the process control or safety programming environment.