The Omron CJ1W-SCU31-V1, also cataloged as the CJ1W-SCU31-V1 Serial Communications Unit, operates as a dedicated hardware component for multi-protocol serial communication execution within Omron CJ-series PLC networks.

Technical Identifier Matrix

• Base Part Number: CJ1W-SCU31-V1
• Brand: Omron
• Classification: CPU Bus Unit
• Revision Identifier: Unit Ver. 1.2 / Unit Ver. 1.3
• Serial Ports: Port 1 (RS-422A/485), Port 2 (RS-422A/485)

Hardware Specifications

Backplane Bus Velocity & Firmware Compatibility

The Omron CJ1W-SCU31-V1 interfaces directly with the CJ-series high-speed backplane bus, operating as a CPU Bus Unit to achieve cyclic data exchange across 25 allocated CIO words and 20 DM words. CPU refresh timing transfers status flags and software switches constantly without interrupting ladder execution cycles. Runtime configuration shifts are executed via the ladder instruction STUP (237) or by triggering the Port Settings Changing Flag in the Auxiliary Area.

Firmware revisions expand interface routing capability without hardware retrofits. Unit Version 1.2 introduces the integrated Serial Gateway engine, which automatically converts incoming FINS commands over the backplane bus into serial protocol frames (including protocol macro execution). Unit Version 1.3 adds native Modbus-RTU slave mode to Port 2, enabling direct connectivity to standard industrial master devices without custom ladder frame parsing.

Package Contents & Ordering Information

• 1x Omron CJ1W-SCU31-V1 Serial Communications Unit
• 2x Terminal Block Connectors (RS-422A/485)
• 1x Hardware Installation Sheet

Field Installation Guidelines

• Rack Mounting: Secure the module onto the CJ-series CPU Rack or Expansion Rack DIN rail until the upper and lower locking mechanisms engage. No slot location restrictions apply within the 16-unit total CPU Bus Unit allocation.
• RS-422A/485 Wiring: Utilize twisted-pair shielded cable for differential signaling on Port 1 and Port 2. Maintain uniform polarity across all network nodes.
• Shield Grounding: Connect cable shielding to the functional ground (FG) terminal using a 360-deg braid clamp at a single grounding node to suppress high-frequency electro-magnetic interference.
• Bus Termination: Enable the built-in terminating resistance via the DIP switch on the front panel for units positioned at the physical ends of an RS-422A/485 transmission line.

Frequently Asked Questions

• What is the maximum backplane current draw for the CJ1W-SCU31-V1?

  The unit draws a maximum current of 380 mA at 5 VDC directly from the CJ-series CPU backplane bus power supply.

• How many CJ1W-SCU31-V1 units can be installed on a single CPU Rack?

  Up to 16 CPU Bus Units, including all CJ1W-SCU31-V1 modules, can be mounted on a single CPU Rack or Expansion Rack.

• Which instruction forces a reload of the serial port setting words from the DM area?

  Executing the ladder instruction STUP (237) forces an immediate reload of the 10 DM configuration words allocated to each serial port.

• Is hot-swapping supported for the CJ1W-SCU31-V1 module on a CJ-series rack?

  No, power to the CPU Rack and Expansion Racks must be completely turned OFF before inserting or removing the CJ1W-SCU31-V1 unit.

• Does the CJ1W-SCU31-V1 support Modbus-RTU slave mode on both ports?

  Modbus-RTU slave mode is supported on Port 2 only, requiring Unit Version 1.3 or later firmware.

• How does the Simple Backup Function interact with the CJ1W-SCU31-V1 protocol macro data?

  The Simple Backup Function backs up internal Protocol Macro data to a Memory Card installed in CJ1-H or CJ1M CPU Units for restoration or comparison.

• What memory areas are allocated to the CJ1W-SCU31-V1 in the CPU Unit?

  The module receives 25 words in the CPU Bus Unit CIO Area and 20 words in the CPU Bus Unit DM Area (10 words per port).

• What grounding practice is required for long-distance RS-485 serial runs?

  Field cabling requires 360-deg braid shielding connected to a low-impedance protective earth terminal to eliminate ground potential loops and signal noise.