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 acts as the primary, which runs the application by executing program logic and operating and .
The other PAC acts as the standby PAC. The primary PAC updates the standby PAC at the beginning of each scan. The standby is ready to assume control within one scan if the primary stops communications.
Primary and standby states are interchangeable. When the PACs are running, either PAC can enter the primary state. When one running PAC becomes primary, the other running PAC may be in the standby or wait state.
The and networks are operated by the primary PAC.
Role of the Hot Standby PAC
The system monitors itself continuously. If a
triggering event occurs, the Hot Standby system switches control to the standby, which then becomes the primary PAC. If the standby PAC stops communications, the primary continues to operate without a backup.
