OMRON CS1W-SCU31-V1: 2-Port Serial Communication Unit for CS1 PLCs

The OMRON CS1W-SCU31-V1 is a high-performance serial communication unit designed for the SYSMAC CS1 series programmable logic controllers. This module provides two independent RS-422A/485 serial ports, enabling robust long-distance communication with industrial field devices. The unit supports multiple communication protocols including protocol macros, Modbus RTU (master and slave), Host Link (SYSMAC WAY), NT Link, and no-protocol communication. With its flexible configuration options and electrical isolation between ports, the CS1W-SCU31-V1 is ideal for connecting HMIs, barcode readers, weigh scales, variable frequency drives, serial printers, and other serial devices to the CS1 PLC system.

Port Specifications

Both ports on the CS1W-SCU31-V1 are RS-422A/485 compatible, supporting 2-wire or 4-wire configurations for multidrop networks. Each port is electrically isolated from the PLC backplane and from the other port, providing 500 VAC isolation to prevent ground loops and noise interference. The maximum cable length is 500 meters, allowing the unit to communicate with remote devices without requiring repeaters. Baud rates are selectable from 1200 to 115200 bps, with configurable data bits (7 or 8), parity (none, even, odd), and stop bits (1 or 2). The unit supports communication with up to 32 nodes on the RS-485 network, making it suitable for distributed I/O applications.

Protocol Macro Function

The protocol macro feature is a key capability of the CS1W-SCU31-V1, allowing users to communicate with virtually any serial device by defining custom send and receive sequences. Using OMRON's 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 calculations (SUM, CRC-16, LRC), and timeout handling. This eliminates the need for complex communication logic in the PLC ladder program, significantly reducing development time and improving code maintainability. The unit also supports Modbus RTU master function for reading and writing coils and registers, as well as Modbus RTU slave function for responding to Modbus requests from a master device.

Configuration and Setup

The CS1W-SCU31-V1 is configured using CX-Integrator or CX-Programmer software. The unit number is set via two rotary switches (SW1 and SW2) on the front panel, allowing addresses from 00 to 63. Port communication parameters are defined in the PLC's DM parameter area using special DM words allocated to the unit. For protocol macro operation, the CX-Protocol software creates and downloads the protocol data. The unit features diagnostic LEDs on the front panel to indicate power, port activity, and communication error status. The DIP switches on the unit allow configuration of Modbus protocol selection for each port and baud rate presets. When using Modbus communications protocol for port B, the appropriate switch settings must be configured, with baud rate options including 19.2 kbps, 38.4 kbps, and 115.2 kbps.

Data Exchange with PLC CPU

The CS1W-SCU31-V1 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. For no-protocol communication, data is transferred using the TXD and RXD instructions in the ladder program. For protocol macro and Modbus operations, the unit automatically transfers data between its buffers and the CPU's DM area, reducing CPU overhead. The unit supports high-speed data exchange with the CPU with cycle times as low as 2 ms for real-time applications.

Environmental Specifications

The CS1W-SCU31-V1 is designed for industrial environments with an operating temperature range of 0°C to 55°C and storage temperature from -20°C to 75°C. Humidity tolerance is 10% to 90% non-condensing. The unit is rated IP20 and is designed for installation inside a control cabinet. Power consumption is 300 mA from the 5 VDC backplane supply; no external 24 VDC is required. The module dimensions are 90 mm height x 31 mm width x 90 mm depth, and it weighs approximately 120 g.

Typical Applications

The OMRON CS1W-SCU31-V1 is widely used for connecting barcode scanners to read product codes into the PLC, interfacing weigh scales for batching systems, communicating with variable frequency drives via Modbus RTU for speed control, linking to HMI panels via Host Link, and connecting serial printers for alarm logging. Its two independent ports can serve two different devices with different protocols simultaneously, reducing the number of communication modules required. The unit is also used for protocol conversion between different serial devices and for extending the communication range of existing PLC systems.