Premium Hot Standby enables the switching of Ethernet services and automatic IP address swapping between the primary and standby TSX ETY modules.

The position of the ETY is unrestricted in the Premium configuration (main rack or extension rack). However, both PLCs must have identical firmware, configurations, and module positions. ETY modules are linked either through the Ethernet switches (one switch per ETY) or an Ethernet crossover cable. By using an Ethernet transceiver, you have an optical connection for longer distances.

To configure the monitored ETY module in Control Expert, set the topology address of the monitored ETY module by selecting the address from a list of existing ETY card addresses in the combo box on the Hot Standby tab of the CPU screen.

The Ethernet port for I/O scanning should be connected to the monitored ETY. If a fault appears on this module (e.g., module hardware failure, broken wire, or cable disconnection) switchover is automatic. If a fault appears on any unmonitored ETY modules, switchover is not automatic; you must design your application to request a manual switchover.

For better performance and more predictable time at switchover, any other required Ethernet services (e.g., Global Data, HTTP server, FTP/TFTP) should be configured in unmonitored ETY modules. These services should not be configured in the monitored ETYs.

For a switchover to occur when an ETY-sync link failure appears in the primary system, one of the two Ethernet services (I/O Scanning or Global Data) must be configured in the monitored ETY. If neither service is configured in the monitored ETY, an ETY-sync link failure does not generate a switchover.

If the monitored ETY module fails, the CPU sends a state change command to all configured ETY modules present on the X-BUS (in the main and extended racks). All ETY modules present in the Hot Standby PLC then swap IP addresses.