MODICON AM-S985-800 Modbus Network Adapter

( Brand: Modicon ), ( Manufacturer Part Number: AM-S985-800 ), ( Part Type: Adapter )

Review MODICON Modbus Plus Network Adapter

The **Modicon AM-S985-800 Modbus Network Adapter (AMS985800)** is a high-performance, industrial-grade communication module designed to seamlessly integrate legacy Modicon PLCs such as the Modicon Quantum, Modicon 984, or Modicon 984P series into modern automation networks. Engineered for reliability and versatility, this adapter bridges the gap between older Modbus RTU/ASCII-based controllers and contemporary SCADA systems, Ethernet networks, or other Modbus-compatible devices. With a robust construction featuring a compact yet durable metal enclosure, the AM-S985-800 is built to withstand harsh industrial environments, including temperature fluctuations, electrical noise, and vibration, ensuring uninterrupted operation in demanding applications such as manufacturing, process control, or energy management.

At its core, the adapter supports both **Modbus RTU** and **Modbus ASCII** protocols, allowing it to communicate bidirectionally with Modicon PLCs while translating data into a format compatible with Ethernet-based networks. This flexibility makes it an ideal solution for upgrading aging automation systems without requiring a full-scale replacement of existing hardware. The device features a **10/100 Mbps Ethernet port**, enabling high-speed data transfer to supervisory control systems, historians, or other networked devices, while its **RS-485 serial interface** ensures reliable communication with Modicon PLCs over long distances, typically up to 1,200 meters (3,937 feet) with proper shielding and termination. Additionally, the adapter supports **Modbus polling, cyclic updates, and event-driven messaging**, providing real-time data acquisition and control capabilities essential for monitoring and optimizing industrial processes.

Security and ease of integration are key considerations in the AM-S985-800 s design. The adapter includes **IPv4 support** with configurable subnet masks and default gateways, allowing for seamless integration into existing TCP/IP networks. It also features **Modbus TCP compatibility**, enabling direct communication with devices that adhere to the Modbus over TCP/IP standard, further expanding its utility in modern automation architectures. Configuration is simplified through a **web-based interface**, accessible via a standard web browser, where users can adjust settings such as baud rate, parity, data bits, stop bits, and timeout parameters for both Modbus RTU and Modbus ASCII modes. For advanced users, the adapter also supports **command-line configuration** via Telnet, providing greater control over network and protocol settings.

The AM-S985-800 is designed with **industrial durability** in mind, featuring a wide operating temperature range of **-40 C to 70 C (-40 F to 158 F)**, making it suitable for deployment in environments such as outdoor enclosures, control rooms, or factory floors. Its **metal housing** provides protection against physical damage, while the **isolated RS-485 port** ensures electrical isolation between the PLC and the network, reducing the risk of ground loops and electrical interference. The adapter also includes **LED indicators** for power, link status, and communication activity, allowing for quick troubleshooting and status verification without requiring access to the configuration interface.

Beyond its technical specifications, the Modicon AM-S985-800 stands out for its **backward and forward compatibility**, enabling seamless migration from older Modicon systems to newer, more efficient automation solutions. Whether used to connect a legacy Modicon 984P to a modern SCADA system, extend the lifespan of an existing control network, or facilitate data logging for historical analysis, this adapter serves as a bridge between past and future automation technologies. Its **plug-and-play design**, combined with robust performance and extensive protocol support, makes it a cost-effective and reliable choice for engineers and technicians looking to modernize their industrial control systems while maintaining operational continuity.

The **Modicon AM-S985-800** is a Modbus RTU/TCP network adapter designed for Schneider Electric PLCs (such as the Modicon Quantum or Premium series) to enable communication over Modbus networks. Below is a detailed analysis of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of the AM-S985-800 Modbus Network Adapter**

1. **Compatibility with Schneider Electric PLCs**

The adapter is specifically designed for Schneider Electric s Modicon Quantum and Premium PLCs, ensuring seamless integration without additional software modifications. It supports both Modbus RTU (serial) and Modbus TCP (Ethernet) protocols, making it versatile for different network setups.

2. **Modbus RTU and TCP Support**

The adapter allows communication over both **Modbus RTU (serial, RS-485)** and **Modbus TCP (Ethernet)**, which is useful for connecting to legacy systems (RTU) or modern IP-based networks (TCP). This dual-protocol support simplifies migration from serial to Ethernet-based communication.

3. **Easy Installation and Configuration**

The adapter is plug-and-play for most Schneider PLCs, requiring minimal configuration. It typically connects via a dedicated port on the PLC (e.g., the "Network" or "Serial" port) and can be configured using the PLC s built-in software (e.g., EcoStruxure Machine Expert or Unity Pro).

4. **Cost-Effective for Basic Modbus Communication**

Compared to full-fledged communication modules (e.g., Ethernet adapters with advanced protocols like OPC UA or PROFINET), the AM-S985-800 is relatively inexpensive. It is ideal for applications where only Modbus is required, avoiding unnecessary complexity or cost.

5. **Reliable for Industrial Environments**

Schneider Electric products are known for their robustness in industrial settings. The AM-S985-800 is designed to withstand harsh conditions (temperature, vibration, etc.), making it suitable for factory automation, process control, and other industrial applications.

6. **Supports Multiple Communication Modes**

The adapter can operate in **master or slave mode** depending on the application, allowing it to act as a gateway between the PLC and other devices (e.g., HMIs, SCADA systems, or other PLCs).

7. **Backward Compatibility**

Since it supports Modbus, which is a widely adopted protocol, the adapter can interface with a broad range of third-party devices (e.g., Allen-Bradley, Siemens, or generic Modbus slaves). This reduces dependency on proprietary solutions.

8. **Low Latency for Time-Critical Applications**

For many industrial applications (e.g., motion control, discrete manufacturing), Modbus RTU offers low-latency communication, which can be sufficient for non-critical data exchange. The adapter ensures efficient data transfer without unnecessary delays.

9. **Easy Troubleshooting**

Schneider Electric provides documentation and support tools (e.g., diagnostic software) to help troubleshoot communication issues. The adapter s simplicity also means fewer points of failure compared to more complex communication modules.

10. **Scalability for Small to Medium Systems**

The AM-S985-800 is ideal for systems where only one or a few PLCs need Modbus connectivity. For larger networks, it can be paired with additional Modbus gateways or routers to expand coverage.

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### **Cons of the AM-S985-800 Modbus Network Adapter**

1. **Limited to Modbus Only**

The adapter does not support advanced protocols like **OPC UA, PROFINET, or Ethernet/IP**, which are increasingly required in modern industrial networks. If your system needs integration with enterprise systems (e.g., MES, ERP) or other high-level protocols, additional modules or gateways will be necessary.

2. **No Built-in Security Features**

Modbus (especially RTU) is not designed with security in mind. The AM-S985-800 does not include encryption, authentication, or firewall capabilities. This makes the network vulnerable to cyber threats if not properly isolated or secured with additional hardware/software (e.g., VPNs, network segmentation).

3. **Serial Port Limitations (RTU Mode)**

Modbus RTU requires a **twisted-pair RS-485 connection**, which can be prone to noise and interference in industrial environments. While RS-485 is robust, it requires proper termination and shielding to avoid communication errors. Ethernet (Modbus TCP) is generally more reliable for long-distance or noisy environments.

4. **No Support for Advanced Modbus Features**

The adapter may not support **Modbus Plus, Modbus/TCP with advanced features (e.g., broadcast messages, large data transfers), or Modbus over TCP/IP with QoS (Quality of Service)**. For complex applications, this could limit functionality.

5. **Deprecated or Obsolete in Some Cases**

While still available, the AM-S985-800 is an older model. Schneider Electric has since introduced newer communication modules (e.g., **AM-S985-800E** or **AM-S985-800P**) with improved features. Some newer PLC models may not require this adapter, as they include built-in Modbus support.

6. **No Built-in Redundancy or Failover**

The adapter does not support **hot-swapping, dual-port redundancy, or automatic failover** to a backup network. If the adapter fails, the PLC s Modbus communication will be disrupted until it is replaced or repaired.

7. **Limited Diagnostic Capabilities**

While basic diagnostics are available, the adapter lacks advanced monitoring features (e.g., real-time error logging, remote diagnostics over the network). For large-scale systems, this may require additional tools or third-party software.

8. **Physical Port Constraints**

The adapter occupies a **dedicated serial or network port** on the PLC. If the PLC has limited ports, this could restrict other communication needs (e.g., Ethernet for OPC UA, USB for programming). Some newer PLCs offer integrated Modbus support, eliminating the need for external adapters.

9. **No Support for High-Speed Data Transfer**

Modbus RTU has a **maximum baud rate of 115,200**, which may be insufficient for high-speed data acquisition or real-time control applications. Modbus TCP is faster but still not as high-performance as proprietary protocols like EtherCAT or PROFINET.

10. **Potential Compatibility Issues with Newer Software**

If you are using the latest versions of Schneider s software (e.g., EcoStruxure, Unity Pro), some features or configurations may not be fully supported with older adapters. Always verify compatibility with your specific PLC and software version.

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### **Conclusion**

The **Modicon AM-S985-800** is a **practical and cost-effective solution** for connecting Schneider Electric PLCs to Modbus networks, particularly in applications where only Modbus RTU or TCP is required. It excels in **simplicity, reliability, and compatibility** with legacy systems, making it ideal for small to medium-sized industrial setups where advanced protocols are unnecessary.

However, its **lack of security features, limited protocol support, and reliance on Modbus (a protocol not designed for modern industrial demands)** make it less suitable for **large-scale, high-security, or high-performance applications**. If your system requires **OPC UA, PROFINET, or advanced Ethernet-based communication**, you may need to supplement this adapter with additional hardware or consider newer Schneider communication modules.

For **basic Modbus communication in a controlled environment** (e.g., a single PLC interfacing with an HMI or SCADA system), the AM-S985-800 remains a **solid choice**. However, for **modern industrial automation, cybersecurity, or high-speed data exchange**, investing in a more advanced communication solution (e.g., integrated Ethernet modules, OPC UA gateways, or PROFINET adapters) would be more future-proof.

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### **Recommendation**

- You need a **simple, low-cost Modbus RTU/TCP solution** for a Schneider Electric PLC.

- Your system **does not require advanced protocols** (e.g., OPC UA, PROFINET).

- You are working in a **controlled environment** with minimal cybersecurity risks.

- You are maintaining a **legacy system** where Modbus is the only viable option.

- Your application requires **high-speed data transfer, real-time control, or advanced industrial protocols**.

- **Cybersecurity is a concern** (consider adding a firewall, VPN, or a dedicated security gateway).

- You need **redundancy or failover capabilities** (e.g., for critical control systems).

- You are using **newer Schneider PLC models** that may have built-in Modbus support, reducing the need for an external adapter.

- For **Ethernet-based Modbus**, check if your PLC supports **built-in Modbus TCP** (e.g., newer Modicon Quantum or Premium PLCs).

- For **modern industrial networks**, explore **Schneider s newer communication modules** (e.g., **AM-S985-800E** with enhanced features).

- If integrating with **enterprise systems**, use an **OPC UA gateway** (e.g., Schneider s **OPC UA Server**) alongside the AM-S985-800.

- For **high-reliability applications

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Please message with any questions or concerns. Used but in working order. Modicon modbus plus network adapter module.

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• PLCs HMIs > PLC Peripheral Modules > PLC Input Output Modules

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