Modicon Premium Automation Platform Hot Standby system

The Premium Hot Standby redundancy offer, which is compatible with Unity Pro software, ensures continuity of operation for an automation system based on a Modicon Premium platform in the event of failure of:

  • Central processing and communication functions.

  • All or part of the I/O system

It is based on the “Primary/Standby” redundancy principle, with complete redundancy of the main processing and communication functions, the use of shared I/O on the Ethernet TCP/IP network, a Modbus link and/or redundancy of in-rack I/O (single-rack confi guration only).

Premium Hot Standby redundant architectures offer an ideal solution for availability requirements when changeover time is not critical. They are designed for processes which can tolerate a lack of control on the part of the Premium PLC lasting up to one second (average changeover time from the “Primary” unit to the “Standby” unit and for updating shared I/O on Ethernet).

They can meet all availability requirements when the purpose of the PLC is to monitor and control an installation in continuous operation, signal incidents to a control station, and transmit command instructions from the supervision manager to various locations on an extensive site.

Example areas of application:

  • Centralized technical management of a public facility (tunnel, airport, signals, etc.)

  •  Control/monitoring of a water treatment or distribution station

  • Electrical technical management

  • Hydroelectric power production

  • etc.


At the centre of the system, there are two Modicon Premium single-rack configurations called the “Primary” PLC and the “Standby” PLC. Their hardware and software configurations are identical (i.e. identical modules in each rack). The offer comprises two processor models (TSX H57 24M and TSX H57 44M) designed specifically for Hot Standby architectures with Unity Pro software (version u 3.1). This dual processor configuration combines the functions of the CPU and redundant coprocessor in the same unit.

The “Primary” PLC:

Executes the application program and manages the I/O, which can take the form of:

  • Field devices on an Ethernet network managed by the I/O Scanning service

  • Field devices on a Modbus master link

  • Sensors and actuators connected to Premium I/O modules on bus X with single-rack configuration

Safeguards the transfer of all data via the “CPU Sync” link to the “Standby” PLC at the start of every cycle.

In the event of a failure affecting the “Primary” PLC, the standby system changes over automatically, whereby execution of the application program and control of the I/O is changed over to the “Standby” PLC within 1.5 cycles, with an up-to-date data context.

An automatic mechanism for the assignment of “IP” and “IP + 1” addresses changes the addresses of the Ethernet network modules with the 2 Premium configurations which manage the field devices. The same mechanism is used for “n” and “n + 1” slave address assignments for Modbus link modules.

Once they have changed over, the “Standby” PLC becomes the “Primary” PLC. Once the faulty PLC has been repaired and reconnected to the standby system, it takes the role of the “Standby” PLC.


Typical architecture
In this type of architecture, the I/O system in Premium PLCs equipped with a dedicated Hot Standby TSX H57 24M/44M processor is defined by the distribution of field devices or equipment on the Ethernet TCP/IP network. From an operational point of view, the following devices or equipment are connected on the same Ethernet TCP/IP network:

  • Client: Twido controller, Modicon PLC, Magelis HMI, W@de remote management module, etc.

  • Modbus TCP server: Advantys OTB/Momentum distributed I/O, Advantys STB I/O islands, Altivar variable speed drives, Lexium servo drives, Inductel/Ositrack identification systems, etc.

The Ethernet I/O Scanning service enables client-server exchanges between a PLC and Ethernet equipment communicating by means of the Modbus TCP protocol. This service can be used to define up to 64 periodic read or write exchanges in the form of a configuration, based on tables of (word type) variables for target devices or equipment. The I/O Scanning service is a function that is available as standard with TSX ETY 4103/5103 Ethernet network modules.

Elements for redundancy

  1. 6, 8 or 12-position non-extendable rack TSX RKY

  2. Power supply module TSX PSY pppM

  3. Premium Hot Standby processor TSX H57 24M/44M

  4. Ethernet TCP/IP network module TSX ETY 4103/5103
    (version >= sv 4.0)

Ethernet TCP/IP ring shared elements

  1. Modicon M340 automation platform featuring processor with built-in Ethernet port BMXP34 2020/2030

  2. Advantys STB modular distributed I/O with network interface module STB NIP 2212

  3. Altivar 61/71 variable speed drive with communication card VW3 A3 310

  4. Advantys OTB Optimum distributed I/O with interface module OTB 1E0 DM9LP

  5. Magelis XBT GT graphic terminal with on-board Ethernet port XBT GT pp30/40

Other possible shared elements:
—Advantys FTM, IP 67 modular I/O
—Momentum distributed I/O -TSX ETG 100/1000 gateway for connecting Modbus devices
—W@de remote management modules (RTU), designed for water applications TSX HEW 315/320/330
—Inductel/Ositrack identifi cation system XGK S1715503 and XGK Z33ETH
—Lexium servo drives with communication card
AMO ETH 001V000 -Preventa XPS MF compact and modular safety PLCs

Ethernet wiring elements:

  1. ConneXium managed switch with 2, 4 or 8 10/100BASE-TX ports TCS ESM 0p3

  2. CPU Sync link, copper crossover cable 490 NTC 000

  3. Copper straight-through cable 490 NTW 000

  4. Copper crossover cable 490 NTC 000


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