The Omron CJ1W-ETN21, also cataloged as the CJ1W-ETN21 Ethernet Unit, operates as a dedicated hardware component for high-speed industrial Ethernet messaging execution within Omron CJ-series PLC systems.

Technical Identifier Matrix

• Base Part Number: CJ1W-ETN21
• Brand: Omron
• Classification: CPU Bus Unit
• Physical Interface: 100BASE-TX (10BASE-T compatible)
• Topology: Star network topology

Hardware Specifications

Backplane Bus Velocity & Firmware Compatibility

The Omron CJ1W-ETN21 interfaces directly with the high-speed CJ-series backplane bus to deliver deterministic FINS messaging and socket communication across industrial Ethernet links. Functioning as a CPU Bus Unit, it routes cyclic I/O data and explicit message frames directly between the CPU memory structures and field Ethernet nodes without causing PLC scan delay.

High backplane throughput supports concurrent socket connections, raw TCP/UDP data frames, and FTP server functions. Internal flash firmware ensures hardware compatibility across CJ1G, CJ1H, CJ1M, and extended CJ-series CPU processors, maintaining full network frame determinism under high-density I/O traffic.

Package Contents & Ordering Information

• 1x Omron CJ1W-ETN21 Ethernet Unit
• 1x Hardware Installation Sheet

Field Installation Guidelines

• Rack Installation: Mount the CJ1W-ETN21 onto the CJ CPU Rack or Expansion Rack DIN rail, pushing horizontally until upper and lower mounting catches lock firmly into position.
• Node Setting: Adjust the front-panel rotary switches to assign the CPU Bus Unit number and binary local IP node address before powering the PLC rack.
• Ethernet Cabling: Route industrial-grade Category 5 or 5e Shielded Twisted-Pair (STP) cabling from the RJ45 port to an industrial Ethernet switch, respecting the 100 m maximum segment limit.
• Shielding & Grounding: Terminate the RJ45 connector shield to the module frame earth. Ground the CPU Rack functional ground (FG) terminal directly to a protective earth rail using a 2.0 mm sq or larger conductor with a 360-deg braid clamp.

Frequently Asked Questions

• What is the maximum current consumption of the CJ1W-ETN21?

  The unit draws a maximum of 370 mA at 5 VDC directly from the CJ-series CPU backplane bus.

• Can the CJ1W-ETN21 operate on 10 Mbps networks?

  Yes, the 100BASE-TX port features auto-negotiation and supports fallback operation on 10BASE-T Ethernet networks.

• What is the maximum point-to-point cable distance for the Ethernet connection?

  The maximum transmission distance is 100 m between the CJ1W-ETN21 unit and the network hub or switch.

• Can the CJ1W-ETN21 be mounted on an Expansion Rack?

  Yes, the module can be located on either the local CPU Rack or any CJ-series Expansion Rack.

• Does the CJ1W-ETN21 support hot-swapping under backplane power?

  No, power to the rack must be completely disconnected before installing or removing the CPU Bus Unit.

• What transmission topology is required for CJ1W-ETN21 network runs?

  The module requires a star network topology utilizing twisted-pair cabling connected to a central switch or hub.

• How are the internal unit number and node address configured?

  The CPU Bus Unit number and local IP node address are set using rotary switches located on the front panel.

• What cabling specifications are recommended for noise mitigation?

  Use Category 5 or 5e Shielded Twisted-Pair (STP) cable with 360-deg braid ground connection to protect against EMI.