Hot Standby Topology

Overview

A Premium Hot Standby system can be configured in many ways. Below are two examples of Premium Hot Standby topology.

Connecting the ETY Modules

The illustration below displays a simple Premium Hot Standby configuration two ETY modules connected by an Ethernet cable; no switches are used.

Premium rack with line terminators

Power supply

Hot Standby processor (TSX H57 24M or TSX H57 44M)

Communication module (TSX SCY 21601 with Modbus PCMCIA TSX SCP 114)

Discrete output module (i.e. TSX DSY 64T2K)

Discrete input module(i.e. TSX DEY 64D2K)

ETY 4103/5103 (minimum firmware version 4.0)

CPU sync link cable

ETY sync link cable

Primary PLC (A)

Standby PLC (B)

Connection block

The link between the two ETY modules is called the ETY-sync link. The two ETYs are called monitored ETYs. Monitored ETY modules manage:

only diagnostic information in the case of exclusive Bus-X configuration
diagnostic information and I/O Scanning if Ethernet I/O devices are connected on the link
diagnostic information, I/O Scanning, and other Ethernet services

NOTE: In the above Premium hot standby configuration, the two monitored ETYs are linked with a crossover cable. No Ethernet devices are connected to the ETY-sync link. A failure on this link does not generate a switchover because the ETY-sync link is not part of the I/O or messaging process.

On the contrary, when Ethernet I/O devices or other equipment are connected to the ETY-sync link, it is necessary to generate a switchover when a cable failure appears on the primary side.

Example of Configuration

The following configuration is:

PLC A and PLC B with the following modules:
- Power supply
- Hot standby processor in slot 0
- Monitored ETY module in slot 2
- Modbus communication (SCY with SCP 114) in slot 4
- In-rack discrete module (DIS IN and DIS OUT) in slots 5 and 6
One switch for simplified schema to connect between Ethernet I/O scanner and SCADA or HMI
A CPU sync link cable between the two CPUs

Connecting Ethernet I/O

The link between the two monitored ETY modules, the ETY sync link cable, transfers information to diagnose the Hot Standby system and manages Ethernet I/O devices and/or other PLCs by configuring Ethernet I/O Scanning and/or Global Data in each monitored ETY.

You can use either of the following architectures:

a low-level architecture, which comprises two Ethernet switches connected together and each ETY connected to one of the switches
a high-level architecture, where several Ethernet ring switches are connected to the Ethernet devices and/or PLCs

For using hubs or switches in different network topologies, such as star, tree, or ring topologies, refer to the ConneXium catalog and the Transparent Ready User Guide.