OMRON CJ1W-SCU32 Serial Communication Unit for CJ Series PLCs

The OMRON CJ1W-SCU32 is a high-performance serial communication module designed for the CJ1, CJ2, and CS1 series PLCs (when used in a CJ rack). It provides two independent serial ports: one RS-232C and one RS-422A/485 (switchable). The unit supports protocol macros, Modbus RTU (master and slave), Host Link (SYSMAC WAY), NT Link, and no-protocol communication. This makes it ideal for connecting HMIs, barcode readers, weigh scales, serial printers, variable frequency drives, and other serial devices to the PLC without custom programming.

Port Specifications

Port 1 is RS-232C (9-pin D-sub male) with a maximum cable length of 15 meters. Port 2 is RS-422A/485 (5-pin removable terminal block) supporting 2-wire or 4-wire configurations, with a maximum distance of 500 meters. Both ports are electrically isolated from the PLC backplane and from each other. Baud rates are selectable from 1200 to 115200 bps, with data bits (7 or 8), parity (none, even, odd), and stop bits (1 or 2) configurable per port.

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Protocol Macro Function

The protocol macro feature allows the CJ1W-SCU32 to communicate with virtually any serial device by defining send/receive sequences using the CX-Protocol software (included with CX-One). Up to 1000 protocol sequences can be stored in the unit’s flash memory. Each sequence can include conditional branching, checksum calculation, and timeout handling. This eliminates the need to write complex communication logic in the PLC ladder program. The unit also supports Modbus RTU master function (reading/writing coils and registers) and slave function (responding to Modbus requests).

Data Exchange with PLC CPU

The SCU32 exchanges data with the CPU via special I/O words allocated in the CIO area and DM area. Each port has a 256-byte send buffer and 256-byte receive buffer. Data can be transferred using simple MOV instructions or using the built-in “TXD” and “RXD” instructions for no-protocol mode. For protocol macro and Modbus, the unit automatically transfers data between its buffers and the CPU’s DM area without user ladder programming. The unit also supports high-speed data links (up to 10 ms cycle) when using the Host Link or NT Link protocols.

Configuration and Setup

Configuration is performed using the CX-Integrator or CX-Programmer software. The unit’s node number (unit number) is set via rotary switches on the front panel (0 to 95). Port settings are defined in the PLC’s DM parameter area (special DM words). Alternatively, the CX-Protocol software can create and download protocol macro data. The SCU32 has 16 diagnostic LEDs (green/red) on the front to indicate power, port activity, and communication errors. The unit supports hot-swapping (installation and removal with power off only, but can be inserted with power off).

Environmental and Mechanical Data

The CJ1W-SCU32 is a CJ-series module measuring 90mm (H) x 31mm (W) x 90mm (D) and weighing 120 g. It requires a CJ-series backplane and consumes 300 mA from the 5 VDC backplane supply (no external 24V needed). Operating temperature: 0°C to 55°C, storage -20°C to 75°C. Humidity: 10% to 90% non-condensing. The unit is rated IP20 and meets CE, UL, and RoHS standards. It is designed for pollution degree 2 environments.

Typical Applications

The CJ1W-SCU32 is widely used for: connecting a barcode scanner to read product codes into the PLC, interfacing a weigh scale for batching systems, communicating with a variable frequency drive via Modbus RTU for speed control, linking to an HMI (Pro-face, Omron) via Host Link, and connecting a serial printer for alarm logging. Its two independent ports can serve two different devices with different protocols simultaneously. The unit is also used in legacy system upgrades where existing serial devices must be retained.

Installation and Ordering

Order number: CJ1W-SCU32. The unit is supplied with a terminal block for port 2 (RS-422/485) and a dust cover. A 9-pin D-sub cable (e.g., CJ1W-CN226) is required for port 1. For RS-422/485 wiring, use shielded twisted-pair cable. The unit is compatible with all CJ1, CJ2, and CS1 (with CJ adapter) CPUs. For applications requiring only one RS-232C port, consider the CJ1W-SCU22. The SCU32 is fully supported by CX-One software version 4.0 or later. OMRON provides a 2-year warranty.