Abstract: According to an aspect of the present invention, any of the redundant gateways selected to operate as an active gateway, is configured to be accessible by a pre-specified address. As a result, any systems communicating with other systems via a gateway may use the same pre-specified address to access the other system irrespective of which of the redundant gateways is operating as an active gateway. The implementation of systems is simplified as a result.

Abstract: In a process control system having a redundant multilayer hierarchical structure, each node of a layer being redundant sequence of events inputs are received from field devices by an input/output processor (IOP). The IOP is a digital input sequence of events (DISOE) IOP, the IOP being the lowest layer of the hierarchical structure. The IOP interfaces with a controller at the next layer of the hierarchy. A method for reliably maintaining a sequence of events function during a failover of any of the redundant nodes, comprising the steps of maintaining a log, a circular list, by the local DISOE. The circular list is a rolling log of all sequence of events data for a predefined time period. When a failover occurs, the new primary commands an event recovery. The event recovery process freezes the log and uses the information in the log to recreate the events data. The freeze operation inhibits background purge activity for the log thereby avoiding the deletion of information past the defined time.

Abstract: A primary (first) and secondary (second) slave (IOP) collect input pulses from a field device, each independently maintaining an interim total number of pulses. A master controller executes a method for maintaining the total number of pulses for the entire process by requesting the interim total number of pulses, a process variable, and a flag from the first IOP by the controller. If the flag indicates no anomaly in the interim total number of pulses or the process variable, the master controller determines a new interim total number of pulse and the process variable since the previous request. The new interim total number of pulses and the process variable is saved in a temporary holding area, such that upon a failover of the first IOP, differences in the interim total number of pulses transmitted by the second IOP can be handled without causing an error in the total number of pulses for the entire process being maintained by the master controller.