Series 90 TCP/IP Triplex Redundancy

The Series 90 TCP/IP Triplex communications enabler allows CIMPLICITY to interface to PLC groups comprising up to 3 PLCs with up to 2 network paths per device.

Cabling redundancy operates in Hot-Standby mode; it communicates to the PLC using the first path while monitoring the second path. It switches automatically, without PLC intervention, to the second path if the first path fails. It continues to monitor the first path and will automatically switch back to the first path on recovery.

PLC redundancy also operates in Hot Standby mode, it communicates with the highest-ranking PLC and automatically switches to a lower ranking PLC in the event of the failure of the highest-ranking PLC. It continues to monitor the PLCs and will automatically switch back to a higher-ranking PLC on recovery.

CIMPLICITY software maintains connection and status information for all the PLCs in a PLC group, but only reads data from the active master. Where unsolicited communication is configured and processed. When unsolicited communication is configured, data will be accepted from any of the PLCs in the group regardless of whether the PLC is the active master. It is recommended that the PLC be setup  so that it will only attempt to send unsolicited data when it is the active master. To the user, the physical devices in the same group are viewed as a single logical device. Points are configured for the logical device thus eliminating the need for duplicate configuration.

Logical devices are configured by entering multiple TCP/IP addresses, either one or two for each PLC in the group. When the enabler starts, the primary PLC is the master and the other PLCs are in Hot-Standby (slave) mode. Under normal operating conditions, the enabler reads data from and writes data to the master PLC, while checking the "health" of the slave PLC(s).

The enabler requires the redundant PLC group to communicate with each other and to indicate (via a mode flag) which programmable controller is the master or is capable of operating as master PLC. The enabler is responsible for selecting the highest-ranking PLC as the active master.

 Important: Since the Mode Address is specified at the port level, all redundant PLCs associated with a port must use the same Mode Address. This means that all PLCs on the port must have the same model type (that is all Series 90-70s or all Series 90-30s or all VersaMax).

More information

PLC redundancy.

Cabling redundancy.

About Series 90 TCP/IP Triplex topics.

 About Series 90 TCP/IP Triplex.