Modicon M580 Hot Standby Frequently Used Architectures System Guide

This document discusses the following: An M580 Hot Standby system is based on two identically configured controllers linked to each other and to the same remote I/O network. If one controller stops communications, the other assumes control of the I/O system. The M580 Hot Standby system is designed for use where downtime cannot be tolerated. The system delivers high availability through redundancy. Two backplanes are configured with identical hardware and software. One of the controllers acts as the primary, which runs the application by executing program logic and operating RIO drops and distributed equipment. The other controller acts as the standby controller. The primary controller updates the standby controller at the beginning of each scan. The standby is ready to assume control within one scan if the primary stops communications. The purpose of a Hot Standby system is to perform a switchover, if needed. A switchover is the immediate transfer of control of the network from the primary controller to the standby controller. The M580 Hot Standby system continuously monitors ongoing system operations and determines if a condition requiring a switchover exists. On each scan, both the primary controller and the standby controller verify the health of the system.