OMRON C20-LK201-EV1 RS-232C Link Adapter for C-Series PLCs
The OMRON C20-LK201-EV1, also referenced as 3G2C7-LK201, is a dedicated communication interface unit designed for C20, C28, C40, and C60 series programmable logic controllers. This adapter adds an RS-232C serial port, allowing the PLC to communicate with host computers, programming consoles, printers, or other serial devices using Omron’s host link protocol.
Functional Capabilities
The LK201-EV1 converts the proprietary peripheral port of older C-series CPUs into a standardized RS-232C interface (9-pin D-sub connector). It supports full-duplex asynchronous communication with baud rates selectable from 300 to 9600 bps, covering most legacy and modern serial equipment. Data format options include 7 or 8 data bits, even/odd/no parity, and 1 or 2 stop bits. The adapter provides optical isolation between the PLC and the serial line, protecting the CPU from electrical disturbances.
Using host link commands (C-mode or FINS via gateway), a supervisory computer can read or write to PLC memory areas, force I/O status, monitor program execution, and upload/download programs. The adapter also allows connection to Omron’s SYSMAC GPRO or NT-series programmable terminals.
Installation and Configuration
The C20-LK201-EV1 mounts directly onto the C-series CPU face using pre-existing mounting holes and connects via a short ribbon cable to the peripheral port. No additional slot is required. It is powered from the PLC’s internal 5V supply, consuming 150 mA. DIP switches on the adapter set baud rate, data format, and unit number for multi-drop networks. The unit includes LED indicators for power (POWER) and transmit/receive activity (TX/RX).
Maximum cable length for RS-232C is 15 meters (50 feet). The adapter is compatible with standard null-modem or straight-through cables. For extended distance or multi-point links, external RS-232 to RS-422 converters can be used. The LK201-EV1 requires no ladder logic programming; it is automatically recognized by most Omron software tools including SYSMAC-CPT, CX-Programmer, and SYSMAC Support Software.
Applications and Legacy Support
The primary use of the C20-LK201-EV1 is to interface legacy C-series PLCs with modern SCADA systems, data loggers, or OPC servers. It is invaluable in plants where older equipment must be integrated into newer control architectures without replacing the entire control system. The adapter also simplifies program backup and troubleshooting by connecting a laptop directly to the PLC.
Although C-series PLCs have been discontinued, the LK201-EV1 remains available for maintenance and system upgrades. It is a reliable component fabricated with through-hole and surface-mount technology, operating in 0 to 55°C ambient temperatures. The unit meets CE and FCC requirements for industrial emissions and immunity.
When used in combination with Omron’s host link protocol, the C20-LK201-EV1 supports both command/response and event-driven reporting. It can be configured for one-to-one or one-to-N (multi-drop) networks using RS-422 adapters. The adapter ensures efficient, stable communication for many years, extending the useful life of legacy C-series automation systems.
