CJ2M-CPU31

Product information

Product Overview

The CJ2M-CPU31 is the entry EtherNet/IP CPU in Omron’s CJ2M range: 2,560 I/O points, up to 40 mountable units, a built-in EtherNet/IP port with Ethernet TCP/IP, USB programming and one option board slot for a serial RS-232C/422/485 board.

This page is written for buyers and maintenance engineers sourcing CJ2M-CPU31 as a new part or a replacement. Every specification below is taken from Omron’s own published catalogue data for this model; no third-party or estimated figures are used, and where Omron publishes two different figures for the same parameter, both are shown.

Omron catalogue position: Automation Systems › Programmable Logic Controllers (PLC) › CJ2. Official catalogue code for this model: CJ2M-CPU31.

Why Buyers Specify This Model

EtherNet/IP built into the CPU

Communication ports per Omron’s catalogue are EtherNet/IP, Ethernet TCP/IP and USB. The EtherNet/IP port supports data links and message communications without occupying a rack slot — the structural advantage of the CJ2M-CPU3[] variants.

One option board slot for serial

A single slot accepts a CP1W-CIF01 (RS-232C), CP1W-CIF11 (RS-422/485) or CP1W-CIF12-V1 (isolated RS-422/485) board, so serial devices are added without an extra unit.

62 mm wide rather than 31 mm

Adding the EtherNet/IP port widens the CPU from 31 mm to 62 mm and raises mass from 130 g to 190 g — worth checking against the panel layout of a CPU13 replacement.

Production ends 31 March 2027

Omron’s official end-of-production notice covers this CPU. Plan accordingly.

Technical Specifications (Official Omron Catalogue Data)

Parameter	Official value
Program capacity	25 K steps
Data memory capacity	64 K words
Logic execution time	0.04 µs
Max. number of expansion units	40
Max. number of local I/O points	2560
Number of built-in digital I/Os	0
Communication port(s)	EtherNet/IP, Ethernet TCP/IP, USB
Product Height (unpacked)	90 mm
Product Width (unpacked)	62 mm
Product Depth (unpacked)	84.5 mm
Product Weight (unpacked)	190 g

Omron publishes two program-capacity figures for the CJ2M range and both are official. The CJ2 series datasheet P059 quotes the ladder program capacity in the 5 K to 60 K step range plus a function-block area equivalent to 20 K steps; the catalogue export used for the table above quotes the combined figure. For this model that is 20 K steps of ladder plus 20 K steps of function-block area, which is where the 40 K step combined figure comes from. Both figures are reproduced here so you can size the application against whichever definition your specification uses.

Source: Omron official product catalogue data for CJ2M-CPU31, published at industrial.omron.eu. Values are reproduced as published by Omron. Where the official data carries a condition or footnote, the headline figure is shown — request the official datasheet for the qualified figure.

Lifecycle & Availability — read this before ordering

Omron’s official product page for this CPU carries a live end-of-production notice: production is planned to end on 31 March 2027. Omron has also published a formal discontinuation notice for the CJ2M CPU range. There is no direct drop-in replacement — the successor platform is the Sysmac NX1P2 / NJ series with Sysmac Studio, and programs are not binary-compatible. If this CPU is running a line you intend to keep, the practical window to secure spare units is open now and closes as the date approaches; after production ends, supply depends on remaining stock.

Two consequences are worth stating plainly. First, for installed machines this CPU remains the correct drop-in continuation and the priority is securing spare units while production runs. Second, for new machines the CJ2M is no longer the right platform choice — the Sysmac NX1P2 or NJ series is Omron’s forward path.

We do not publish stock or lead time as fixed figures on this page. Send the quantity and the required date and we will confirm what can be secured for that specific position.

Official Documentation

These are Omron’s own documents for this model and its family. Download them directly from Omron’s document server:

• Datasheet: p059 cj2-series programmable controller datasheet en
• Manual: w472 cj2 cpu units hardware users manual en
• Manual: w473 cj2 cpu units software users manual en
• Manual: w486 cj2m-md21x pulse i o module users manual en
• Manual: w465 cs cj-series ethernet ip units operation manual en

Full technical detail — conversion periods, wiring diagrams, derating and installation requirements — is in these documents. If you need a specific figure we do not show here, ask and we will point you to the exact page rather than paraphrase it.

Matching Accessories and Spare Parts

The list below is Omron’s own accessory and spare-part association for this model — the parts Omron itself couples to it for commissioning and for maintenance. Buying them together avoids the usual problem of a spare unit arriving without the bracket, key or battery needed to run it.

Genuine spare parts

Part	Official description
CJ1W-BAT01	Battery for CJ1M PLCs
CJ1W-TER01	End plate for CJ1 CPU rack or expansion rack. Only required as spare part.

Associated accessories

Part	Official description
CJ1W-CIF11	RS-485 adaptor, 2 or 4 wire, connects directly to RS-232C 9-pin port for serial PLC link, screw terminals on RS-485 side
CJ1W-IC101	Expansion I/O control unit, connects to right hand side of CPU
CJ1W-II101	Expansion I/O interface unit, connects to left hand side of expansion I/O rack, up to 3 expansion racks
CJ1W-PA202	Power supply unit, 100-240 VAC, output capacity: 14 W
CJ1W-PA205R	Power supply unit, 100-240 VAC, output capacity: 25 W, with RUN output
CJ1W-PD022	Power supply unit, 24 VDC, output capacity: 19.6 W
CJ1W-PD025	Power supply unit, 24 VDC, output capacity: 25 W
CJ2M-MD211	Pulse I/O Module for CJ2M, NPN with 10 inputs (four interrupt/quickresponse and two high-speed counter inputs) and 6 outputs (two pulse and two PWM outputs)
CJ2M-MD212	Pulse I/O Module for CJ2M, PNP with 10 inputs (four interrupt/quickresponse and two high-speed counter inputs) and 6 outputs (two pulse and two PWM outputs)
CP1W-CIF01	RS-232C serial communication option board for use with CP1 PLC
CP1W-CIF11	RS422/485 serial communication option board for use with CP1 PLC
CP1W-CIF12-V1	CP1 RS422/485 (isolated 500 m max.) serial communication option board

Omron lists 26 associated accessories for this model in total; the 12 most commonly ordered are shown. Ask if you need the complete list.

Ordering This Part

Send us the full catalogue number CJ2M-CPU31, the quantity, your delivery address and the date you need the goods. If the part is a replacement, attach a photograph of the existing unit’s nameplate — it removes any doubt about the revision, the output type or the supply voltage, which are the three things that most often cause a wrong part to be shipped.

We do not publish stock, condition or lead time as fixed figures here, because they change: they are quoted per enquiry against the quantity and date you actually need. If a machine is down, say so and give us the required window — that is the information that determines how we source it.

Frequently Asked Questions

What is the difference between CPU31 and CPU33?

Program capacity only, on Omron’s naming convention: the CPU31 carries 5 K steps of ladder program (25 K steps combined with the function-block area) and the CPU33 carries 20 K steps (40 K combined). I/O ceiling, dimensions, ports and weight are identical.

Can I add more serial ports later?

The CPU provides one option board slot, so one serial board only. Further serial or fieldbus connections are added as CJ1W units on the rack (CJ1W-SCU or CJ1W-Serial units).

Does the built-in EtherNet/IP port support data links?

Yes, but capacity differs from the CJ2H. Omron’s datasheet gives a maximum of 2,000 tag data links on the CJ2M-CPU3[] against 20,000 on the CJ2H-CPU6[]-EIP, with a total data link capacity of 8,704 words. Size large data-exchange applications against those two numbers, not against the CJ2H figures.

Should I buy spare units before production ends?

For a critical line, yes. Producing a CJ2M after March 2027 depends on remaining stock. Tell us the quantity and we will confirm what can be secured.