SCHNEIDER 140NOM21100 Electric I/O Module

I. Overview

Adopting an industrial-grade bus communication architecture, this module is highly compatible with the backplane bus protocol of the Quantum system, enabling efficient data flow between the control layer and the monitoring layer. It is a key device for building centralized communication networks in medium-to-large industrial automation scenarios.

II. Technical Parameters

III. Functional Features

• Flexible Topology and Redundancy Assurance: The module supports two topologies: bus and ring. The bus topology adapts to simple linear deployment scenarios, such as assembly line equipment communication. The ring topology builds a redundant network through dual RJ45 interfaces; if a link fails, data can be transmitted through the reverse link to avoid communication interruption. In the PLC control system of power substations, the ring topology can effectively improve the transmission reliability of power supply control signals and reduce the risk of power outages caused by communication failures. Meanwhile, the module has a built-in terminal resistor, which can be enabled via a DIP switch without additional external resistors, simplifying the deployment of bus head and tail nodes.
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• Master-Slave Collaboration and Multi-Node Communication: As a core node of the Modbus Plus bus, the module can be flexibly configured as master or slave mode. In master mode, it can actively poll 31 slave devices on the bus (e.g., intelligent meters, distributed I/O) to collect data and issue control commands. In slave mode, it responds to access requests from the master and uploads the operating data of the local PLC. In the reactor control system of a chemical workshop, the 140NOM21100 of the central Quantum PLC is configured as the master, polling temperature and pressure data from each reactor slave while issuing process parameter adjustment commands to achieve multi-device collaborative control.
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• High-Speed Data Interaction and Cache Optimization: The module interacts efficiently with the CPU via the 10Mbps backplane bus. It encapsulates the data in the CPU's output image area into Modbus Plus protocol frames and sends them to the bus. At the same time, it parses the data received from the bus and writes it into the CPU's input image area. The data transmission delay is ≤3ms, meeting real-time control requirements. The built-in 8KB communication buffer adopts a "First-In-First-Out" mechanism, which can temporarily store data from multi-node interactions and avoid data loss caused by CPU busyness. In metallurgical steel rolling scenarios, this caching capability ensures synchronous collection of speed data from multiple rolling mills and issuance of commands.
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• Industrial-Grade Anti-Interference and Reliability: At the hardware level, a 2500Vrms photoelectric isolation design is adopted between the bus and the backplane, which effectively resists electromagnetic interference generated by motor start-stop and frequency converter operation in industrial sites and prevents interference signals from entering the PLC system and causing misoperation. At the software level, a CRC data verification mechanism is used to ensure the integrity of data transmission. In harsh environments such as cement production workshops with high dust and strong interference, the module can still stably transmit equipment operation data to ensure continuous production.
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• Convenient Diagnostics and O&M Optimization: The module integrates rich diagnostic functions. Engineers can read the module's communication status, node address, fault code and other information via Unity Pro software, and can also judge the operating status through the panel indicators: the "PWR" light on indicates normal power supply, the "BUS" light flashing indicates active bus communication, and the "FAULT" light on indicates a fault. When a node address conflict or link interruption occurs, the module will report specific fault codes to help engineers quickly locate the problem. In addition, it supports online firmware upgrade, enabling version updates without disassembling the module, which reduces O&M costs.

IV. Working Principle

1. Initialization and Parameter Configuration: After the module is installed in the functional slot of the Quantum backplane, it obtains DC 5V power through the backplane bus and establishes communication with the CPU. Engineers configure the module parameters via Unity Pro software:

• Network parameters: Set node address (1-31), topology type (bus/ring), and terminal resistor status.

• Communication parameters: Configure master/slave mode, polling cycle, and register address and length for data interaction.

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1. Data Encapsulation and Transmission (Master Mode): Based on the control logic, the CPU writes the control commands or parameters to be issued into the module's send buffer. The module encapsulates the buffer data into protocol frames according to the Modbus Plus protocol specification. The frame structure includes target node address, data type, data length, check code and other information. Then, it sends the protocol frame to the Modbus Plus bus through the bus interface, while monitoring the bus occupancy status to avoid data conflicts. For example, when the master issues a speed adjustment command, it will specify the target slave address to ensure the command is accurately delivered.
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3. Data Reception and Parsing: The module monitors the protocol frames on the bus in real time through the bus interface. When it detects that the target address is its own node address, it receives the frame and performs CRC verification. After successful verification, it parses the data content in the frame, extracts control commands or collected data, and writes them into the module's receive buffer. The CPU reads the data in the receive buffer through the backplane bus, updates the input image area or executes the corresponding control logic. If the verification fails, the module discards the frame and records a communication error log.
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5. Ring Topology Redundancy Handling: In the ring topology configuration, the two RJ45 interfaces of the module are respectively connected to the two ends of the ring link. During normal operation, only the main link transmits data, and the backup link is in the monitoring state. If the main link fails (e.g., network cable breakage), the module detects the loss of the bus signal, immediately switches to the backup link to receive data, and reports the link fault information to the CPU through the backplane bus. After the fault is restored, it automatically switches back to the main link. The entire switching process takes ≤100ms and does not affect system operation.

V. Common Faults and Solutions