Omron CJ2 PLC EtherNet/IP Integration and CJ1 Migration Reference

Overview

The Omron CJ2 series is the second-generation successor to the CJ1 modular PLC platform, retaining the CJ1 backplane mechanics while adding a built-in EtherNet/IP scanner, faster instruction execution, expanded memory map, and refined programming environment support. Released in 2009 as an evolutionary expansion of the CJ1 line, the CJ2 does not replace the CJ1 platform; both families remain installable in the same engineering ecosystem for an extended overlap period. The headline change in CJ2 is native EtherNet/IP connectivity on selected CPU models, eliminating the requirement for an external CJ1W-EIP21 communication unit in many topologies.

This reference applies to engineering teams that already operate CJ1 installations, system integrators evaluating migration paths, and OEMs designing new machines that need deterministic Ethernet messaging alongside the established Omron instruction set.

CJ2 Product Line Architecture

The CJ2 family is split into two branches distinguished by processing power and instruction set coverage:

Both branches share the same CJ-series backplane, the same I/O unit catalog (CJ1W basic and high-density units), the same expansion rack rules, and the same peripheral bus behavior. The choice between branches is driven by program memory ceiling, scan-time requirements, and the need for built-in EtherNet/IP.

CJ2H vs CJ2M CPU Specifications

The table below captures the principal CPU specifications documented for the CJ2 line at announcement. Verify exact program/step capacity in the hardware user's manual (W472) before committing to a build, because Omron periodically issued capacity revisions for high-end CPU68 variants.

EtherNet/IP Integration

The defining capability of the CJ2 platform is the integration of EtherNet/IP directly onto the CPU chassis, available as a built-in port on -EIP-suffix CJ2H CPUs and achieved externally on CJ2M installations using a CJ1W-EIP21 unit.

Built-in EtherNet/IP on CJ2H-CPU6_-EIP

• Two-port embedded switch (DLR-ready in firmware 2.0+): device-level ring and star topologies are supported without external switches where ring redundancy is required.
• Functions: CIP messaging client/server, I/O connections (originator and target), tag data link with configurable connection counts (typical allowance: up to 32 CIP connections per CPU).
• Maximum cyclic data exchange rate: 1 ms RPI minimum, subject to connection count and CIP path complexity.
• IP configuration: static, BOOTP, or DHCP, configured through CX-Programmer or directly with the rotary switches (last octet override).

CJ1W-EIP21 on CJ2M

When the CJ2M is selected for cost reasons and EtherNet/IP is required, the CJ1W-EIP21 occupies one slot of the CJ1W rack. The connection topology, CIP path, and tag data link configuration are identical to the built-in port model. Two CJ1W-EIP21 units can be installed on a single CPU to provide physically separated subnets (e.g., machine-level vs. plant-level) without additional switches.

EtherNet/IP Commissioning Parameters

CIP Routing and CIP Message Instructions

The standard CIP messaging instructions are available on the CJ2 with the same ladder mnemonics inherited from CJ1: CMND (generic CIP/CPU-bus command), SEND/RECV (network), and MSG (CIP message). The CIP route path syntax follows the convention:

Example: a CIP message to a PowerFlex drive on EtherNet/IP at IP 192.168.1.50 through the CPU built-in port uses the network byte string 01 00 00 00 C0 A8 01 32 (Ethernet/IP routing prefix + IPv4 address).

CJ1 Backward Compatibility and Migration

One of the central design goals of the CJ2 was to make a migration "additive": existing CJ1 projects must load, simulate, and run on a CJ2 CPU with minimal ladder rework. The compatibility surfaces are explicit:

Program Conversion Procedure

1. Open the existing .cxp in CX-Programmer 9.x or later. The Convert dialog reports unsupported instructions; address these by verifying no legacy CJ-series libraries were used without an updated FB.
2. Reallocate I/O tables from the new CPU configuration. CJ2 inherits CJ1 allocations when the rack is physically identical.
3. Rebuild any tag-data-link tables if the migration included switching from CJ1W-ETN21 + custom UDP messaging to the native EtherNet/IP port.
4. Validate conversion with the Compare tool against the original .cxp; pay particular attention to PRV (pulse rate) instruction operand formats, which were tightened in CJ2.
5. Download to a CJ2 CPU and verify each task (cyclic, interrupt) using the Watch Window before fielding the equipment.

Software Environment: CX-Programmer and CX-One

CX-Programmer version 9.0 (or later) is the supported programming IDE for the CJ2 line, typically delivered through the CX-One suite. CX-Programmer 7.x will read a CJ2 project but cannot create one nor will it push a project to the CPU via USB/Ethernet; the editor must be upgraded.

Instruction Set Enhancements in CJ2

The CJ2 instruction set is a superset of the CJ1 set. Notable additions include:

• Advanced function blocks ("FB" with structured local variables) for reusable packaging.
• Symbolic variable access from ladder (e.g., Motor1_Speed instead of pure address D100).
• Enhanced STUP (serial setup) parameters supporting RS-485 multidrop on CPU option board.
• Improved string instructions: MOV$, +$, LEN$, LEFT$, RIGHT$, MID$, with expanded buffer boundaries.
• Trigonometric and floating-point extensions: SIN, COS, TAN, ASIN, ACOS, ATAN, EXP, LOG, POW with single and double precision operands.
• Compact stack-based operations for high-throughput event handling.

Memory Areas (Address Map Summary)

Hardware Installation Notes

Rack Layout Rules

Three classes of units occupy a CJ2 chassis:

1. CPU Unit — slot 0 only.
2. CPU Bus Units — CJ1W-ETN21, CJ1W-EIP21, CJ1W-SCU21, etc. Up to 16 per CPU.
3. Basic / Special I/O Units — Remaining slots up to rack capacity.

A CPU bus unit's allocation letters and dip-switch position define the DM and CIO ranges used by ladder code; changing slot order between commissioning and field service typically requires re-allocating those areas in the I/O table.

Power and Grounding

• Use CJ1W-PA202 (100–240 VAC) or CJ1W-PD022 (24 VDC) power supply units. The PD022 must be sourced from a regulated, fused 24 VDC rail.
• Ground the CPU via the protective earth (PE) terminal at the power supply; resistance to ground should be 100 Ω or less (Class D grounding for industrial control per local code).
• Maintain separation between analog signal wiring (CJ1W-AD041/DA041) and AC power or VFD power cables; observe 100 mm minimum parallel clearance unless shielded cable is used.

Memory Card Use

The CJ2H supports CompactFlash (later firmware revisions support SD) for project backup and recipe storage. The card must be FAT16-formatted and must not contain files the CPU does not control. Inserting a card with foreign files can stall boot; remove power before insertion and confirm the SLOT indicator on the CPU reads FILE before the program download completes.

CJ2H vs CJ1M/CJ1G Migration Trade-offs

Troubleshooting Matrix (EtherNet/IP + Generic CJ2)

Field-Commissioning Checklist

1. Confirm chassis and power supply meet the calculated load budget. Sum the CJ1W unit current ratings against the supply's maximum.
2. Set the rotary IP-address octet switches to the intended value before applying power.
3. Run an I/O verification pass: walk each input and output physically and confirm the corresponding CIO bit transitions in CX-Programmer Watch.
4. Verify cyclic, interrupt, and (where used) scheduled tasks execute by reading TK00–TK31 flags.
5. Connect Network Configurator to the built-in EtherNet/IP port. Open the connection diagnostics and check that the device appears online, that the CIP identity object returns the expected vendor/product codes, and that each originator connection reports "Established."
6. Backup the project to the CompactFlash card (CJ2H) and to a protected folder on the engineering laptop before releasing the machine.
7. Document the IP addressing, subnet mask, gateway, and connector pin-outs of any RS-232C option board.

Frequently Asked Questions