OMRON CS1W-EIP21 EtherNet/IP Unit

The OMRON CS1W-EIP21 is an EtherNet/IP communication unit designed for the CS1 series of programmable logic controllers. This module provides high-speed, deterministic data exchange between CS1 PLCs and other EtherNet/IP devices such as remote I/O, HMIs, drives, and other PLCs. The unit supports both tag data links (implicit messaging) and explicit messaging, making it suitable for real-time control and information integration.

Product Overview

The CS1W-EIP21 is part of OMRON's CS1 series of Special I/O Units, adding EtherNet/IP industrial Ethernet connectivity to CS1, CS1D, and CJ1 (with adapter) PLC systems. EtherNet/IP (Ethernet Industrial Protocol) is a widely adopted industrial network standard that uses standard Ethernet and TCP/IP technology combined with the Common Industrial Protocol (CIP). The CS1W-EIP21 allows CS1 PLCs to participate in high-performance real-time control networks, exchanging data with up to 256 connections. The module includes a built-in Ethernet switch with two ports (2-port version), allowing daisy-chain wiring without requiring an external switch. The module also supports standard TCP/IP services including FTP for file transfer and SMTP for email notifications. The CS1W-EIP21 is configured using OMRON's CX-Integrator or the built-in web server. The module occupies one slot in the CS1 rack and requires no external power supply.

Technical Specifications

The CS1W-EIP21 supports 10BASE-T and 100BASE-TX Ethernet, with auto-negotiation for speed and duplex. The module has two RJ45 ports (switch function) allowing daisy-chain connection of up to 50 units without external switches. The maximum transmission distance per segment is 100 meters (using Cat5e or better cable). The module supports both implicit (real-time) and explicit (message) communication. For tag data links, the module supports up to 256 connections total, with a maximum packet rate of 10,000 packets per second. The data link can be configured with up to 8 connections for sending and 8 for receiving per unit. Each connection can transfer up to 504 bytes of data. The total data capacity is 8 KB for output (from PLC to network) and 8 KB for input (from network to PLC). The module supports a maximum of 256 tag sets. The cyclic communication period can be set from 0.5 ms to 10,000 ms in 0.5 ms increments, depending on network load and device capabilities. The module's power consumption is 0.35 A at 5V DC from the PLC backplane. The operating temperature range is 0°C to 55°C.

Tag Data Link (Implicit Messaging)

The CS1W-EIP21's tag data link function enables cyclic, real-time data exchange with other EtherNet/IP devices. Unlike conventional PLC-to-PLC communications that require programming of send/receive instructions, the tag data link automatically transfers specified data areas at configured intervals. The user defines tag sets, which are collections of PLC memory addresses (CIO, DM, EM, etc.) that will be sent or received. The tag data link supports both point-to-point and multicast communication. For example, a CS1 PLC can send its data to multiple receivers using a single multicast packet. The data link can be configured for high-speed applications such as motion control (with compatible drives) or for slower process data exchange. The module includes a "data link status" area that provides real-time health monitoring of each connection, allowing the PLC program to detect communication failures and take appropriate action. The tag data link can be started and stopped under program control.

Explicit Messaging

In addition to cyclic data links, the CS1W-EIP21 supports explicit messaging for on-demand data exchange. Explicit messages are used for configuration, diagnostics, and aperiodic data transfer. The module provides instructions (CMND or EIPRD/EIPWRT) that can be used in the PLC program to send explicit messages to other devices. For example, the PLC can read the status of a remote drive, change a parameter in a servo amplifier, or trigger a function block in another PLC. The CS1W-EIP21 supports both UCMM (Unconnected Message Manager) and Class 3 connections for explicit messaging. Up to 32 simultaneous explicit message connections are supported. The module also supports CIP routing, allowing messages to pass through multiple EtherNet/IP bridges to reach devices on other networks (e.g., DeviceNet).

Configuration and Setup

The CS1W-EIP21 is configured using OMRON's CX-Integrator software (part of CX-One) or via the built-in web server. Configuration includes setting the IP address (DHCP, BOOTP, or fixed), subnet mask, default gateway, and communication parameters. The tag data link is configured by creating a "tag set" that maps PLC memory areas to network variables. CX-Integrator provides a graphical interface for discovering devices on the network and dragging/dropping connections. The configuration can be saved to a file and downloaded to multiple units. The module also supports automatic configuration using the "EDS" files (Electronic Data Sheets) of connected devices. The module's front panel includes a 7-segment LED display showing IP address segments and status codes. There are also LEDs for power, run, error, and link/activity. The module includes a built-in web server that allows monitoring of communication status and diagnostic information using a standard web browser.

Integration with OMRON PLCs

The CS1W-EIP21 is designed for seamless integration with CS1 and CS1D PLCs. The module appears in the PLC's I/O table as a Special I/O Unit and is assigned a unit number (0 to 95). The PLC's CPU automatically allocates memory areas for the module's status and data link parameters. The tag data link data is mapped to CIO (Core I/O) and DM (Data Memory) areas, which can be used in the PLC program just like any other data. The module also supports direct access to CS1 PLC memory via CIP explicit messages from other devices. For example, an HMI can read and write PLC memory through the EtherNet/IP connection using standard CIP services. The module is compatible with OMRON's CX-Programmer for online monitoring of tag data links. The CS1W-EIP21 can also be used in CJ1 series PLCs with the CS1W-EIP21 plus a CJ1W-CLK23 or similar adapter (check compatibility).

Network Topologies and Wiring

The CS1W-EIP21 supports star, daisy-chain, and ring topologies (with external switches). The two-port switch built into the module allows daisy-chaining of multiple units, reducing wiring in control cabinets. In a daisy-chain configuration, the total number of units is limited by the propagation delay and cable length; up to 50 units can be chained with 100-meter segments between each. For star topology, external Ethernet switches are used. The module supports auto-MDI/MDI-X, so both straight-through and crossover cables can be used. For high-noise environments, shielded Cat5e or Cat6 cable is recommended. The module's Ethernet ports are isolated from the PLC backplane to prevent ground loops. The module supports quality of service (QoS) for prioritizing real-time traffic.

Security Features

The CS1W-EIP21 includes several security features to protect against unauthorized access. IP address filtering can be configured to allow communication only from specific IP addresses. The module supports disabling of unused protocols (e.g., HTTP, FTP, SNMP) to reduce attack surface. Password protection is available for the web server and for configuration changes. The module also supports 802.1X port-based authentication for network access control. However, the CS1W-EIP21 does not include encryption (e.g., IPsec or TLS); for secure communication in untrusted networks, it is recommended to use a VPN or firewall. The module's firmware can be updated to address security vulnerabilities; updates are available from OMRON.

Applications

The CS1W-EIP21 is used in a wide range of industrial applications requiring real-time control over Ethernet. Typical applications include machine automation where multiple PLCs need to coordinate (e.g., packaging line with several stations); remote I/O where distributed I/O blocks (e.g., OMRON NX series) are connected via EtherNet/IP; drive and motion control where servo drives and VFDs receive speed/torque commands over the network; data collection where the PLC sends production data to a SCADA system or MES; and system integration where the PLC must exchange data with non-OMRON devices (e.g., Allen-Bradley PLCs using EtherNet/IP). The module's high data rate and low latency make it suitable for applications requiring synchronization in the millisecond range.

Troubleshooting and Diagnostics

The CS1W-EIP21 provides comprehensive diagnostic tools to identify network problems. The front panel LED display shows the unit's IP address and error codes. The module includes a built-in web server with pages showing connection status, packet statistics, error logs, and port diagnostics. Using CX-Integrator, users can perform network scan to discover devices, monitor tag data link status (packet loss, cycle time), and capture network traffic for analysis. The module also supports the Simple Network Management Protocol (SNMP) for integration with network management systems. Common issues include IP address conflicts, duplicate node IDs, excessive network traffic causing missed packets, and cabling problems. The module's event log stores up to 100 events with timestamps.

Compatibility and Ordering Information

The CS1W-EIP21 is compatible with CS1, CS1D, and CJ1 (with CS1W-CLK23 adapter) PLCs. It requires CX-Programmer version 5.0 or higher and CX-Integrator version 2.1 or higher for configuration. The module is certified for ODVA (Open DeviceNet Vendor Association) conformance, ensuring interoperability with other EtherNet/IP devices. The module's hardware revision is indicated on the side label; newer revisions include improved performance and security features. The module can be mounted in any slot of the CS1 rack, but the total number of communication units (including other Ethernet, Controller Link, etc.) is limited by the PLC's CPU capabilities (typically up to 2 to 4 communication units depending on CPU model). For CS1D redundant systems, two CS1W-EIP21 units can be used in the active and standby CPU racks.

Maintenance and Firmware Updates

The CS1W-EIP21 requires no routine maintenance other than keeping the unit clean and ensuring proper ventilation. Firmware updates are available from OMRON to add features or fix issues. Updates are performed using CX-Integrator and a special firmware file. The module's configuration can be saved to a memory card in the PLC or to a computer for backup. In case of failure, the module can be replaced without powering down the entire system if the PLC supports online replacement (CS1D only). For CS1, the system must be stopped. The module's expected lifespan is 5-10 years in industrial environments, after which electrolytic capacitors may degrade.