CJ1W-SCU31

Product information

Product Overview

A CJ-series CPU Bus Unit that adds two RS-422A/485 serial ports to a CJ1, CJ2 or CP1 (with CJ Unit Adaptor) PLC rack. Omron’s own catalogue carries this unit as CJ1W-SCU31-V1 — the “V1” revision of the model you have listed.

This page is written for buyers and maintenance engineers sourcing CJ1W-SCU31 as a new part or a replacement. Every specification below is taken from Omron’s own published data for this model; no third-party or estimated figures are used, and where Omron publishes two different figures or two variants for the same parameter, both are shown.

Omron catalogue designation: CJ-series Serial Communications Unit. Official catalogue code for this model: CJ1W-SCU31-V1.

Why Buyers Specify This Model

Why two RS-422A/485 ports and not RS-232C

This variant exists for multi-drop networks. RS-422A/485 carries up to 500 m of total cable with up to 32 units on one link, where RS-232C stops at 15 m and one-to-one. If your line already has several controllers or inverters daisy-chained, this is the port configuration you want, not the SCU22.

Protocol macro means you do not need a gateway

Protocol macro lets the Unit talk to a third-party device directly from ladder logic using a protocol you register with CX-Protocol — up to 20 protocols, 1,000 sequences and 300 messages. That is what removes the separate protocol converter box from the panel.

Modbus-RTU Slave and Serial Gateway depend on unit version

Both functions arrived by firmware revision: Serial Gateway, No-protocol and 1:1 Host Link at Unit Ver. 1.2, Modbus-RTU Slave at Unit Ver. 1.3. If your integration depends on either, confirm the unit version on the label before ordering — this is the single most common cause of a wrong SCU31 being supplied.

16 CPU Bus Units is the real ceiling

The rack limit of 16 CPU Bus Units includes Controller Link, Ethernet and DeviceNet units. On a densely populated CJ2 rack, count the other CPU Bus Units before assuming you can add two or three SCUs.

Technical Specifications (Official Omron Data)

Parameter	Official value
Device name	Serial Communications Unit
Classification	CJ-series CPU Bus Unit
Port 1	RS-422A/485
Port 2	RS-422A/485
Selectable protocols (per port)	Host Link, protocol macro, NT Link, loopback test. Unit Ver. 1.2 or later also supports Serial Gateway, No-protocol and 1:1 Host Link; Unit Ver. 1.3 or later also supports Modbus-RTU Slave.
Baud rate	1,200 / 2,400 / 4,800 / 9,600 / 19,200 / 38,400 / 57,600 / 115,200 / 230,400 bps (default 9,600 bps). 230,400 bps requires the CJ1W-SCU@2).
Communications distance (RS-422A/485)	CJ1W-SCU@1-V1: 500 m max. total cable length, T-branch lines 10 m max. Multidrop connection, up to 32 Units (unit numbers 0 to 31).
Number of mountable Units	A total of up to 16 CPU Bus Units per CPU Rack or Expansion Rack, which gives a system total of up to 32 serial ports.
Data exchange with the CPU Unit	25 words allocated in the CPU Bus Unit CIO Area; 10 words per serial port (20 words total) in the CPU Bus Unit DM Area.
Current consumption	380 mA at 5 V
Weight	110 g max.
International standards	UC1, N, L, CE
General specifications	Conforms to general specifications for the CJ Series.

Omron does not supply the serial port connector with the Unit. The catalogue names plug XM3A-0921 and hood XM2S-0911-E (or equivalents) as the mating parts — order them separately.

Lifecycle, revision and the “V1” suffix

Omron’s published model number for this unit is CJ1W-SCU31-V1. The “V1” is part of the official catalogue number, not a supplier’s marker. The same datasheet also lists CJ1W-SCU32 and CJ1W-SCU42 as the high-speed types with up to 230,400 bps and 1,200 m RS-422A/485 distance.

Practically: for a replacement on an existing machine, match the unit version that is already fitted, because the available protocol set depends on it. For a new machine, the SCU32/SCU42 are the better-specified choice. Quote the full number including the revision and we will supply against it rather than against the short form.

Availability, condition of supply and lead time are quoted per enquiry because they depend on quantity and on where the goods are held. We do not publish stock or lead time as fixed figures on this page. Tell us the quantity and the date you need it and we will answer with a firm position rather than a promise.

Official Documentation

The specifications on this page are taken from Omron’s own documents. You can download the source document directly:

• CJ-series Serial Communications Units — CJ1W-SCU Datasheet — https://edata.omron.com.au/eData/PLCs/CJ1/CJ1W-SCU_DS.pdf

Full technical detail — wiring diagrams, derating curves, installation requirements and the complete ordering tables — is in that document. 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.

Ordering This Part

Send us the full catalogue number CJ1W-SCU31-V1 (and the model number CJ1W-SCU31 you are replacing), the quantity, your delivery address and the date you need the goods. If it 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

Is CJ1W-SCU31 still available, or has it been replaced?

Omron’s current catalogue positions the CJ1W-SCU32 and CJ1W-SCU42 as the high-speed units of this family — they add 230.4 kbps operation and extend the RS-422A/485 distance to 1,200 m. The CJ1W-SCU31-V1 remains the documented entry in the same datasheet. For an installed machine, matching the existing unit keeps the wiring and unit-number settings unchanged; for a new build, look at the SCU32.

Which is this — a Board or a Unit?

It is a Unit. It mounts in a CJ-series rack slot and is a CPU Bus Unit. The CS1W-SCB@1-V1 boards with the same port layout mount inside a CS1 CPU Unit instead — they are not interchangeable.

Can it talk to a temperature controller or a smart sensor?

Yes. Compoway/F and Modbus-RTU are both in the protocol macro library, and Serial Gateway is the standard route to Omron components. Confirm the unit version as noted above.

What connectors do I need?

None are in the box. Order the plug and hood (XM3A-0921 / XM2S-0911-E or equivalent) with the Unit so commissioning is not held up.