Omron C200HW-PRT21 Profibus DP Slave Unit

The Omron C200HW-PRT21 is a communication interface module that allows Omron C200H series programmable logic controllers to operate as a slave device on a Profibus DP fieldbus network. Profibus DP (Decentralized Peripherals) is one of the most widely used industrial communication protocols, particularly in European machine building and process automation. By installing the C200HW-PRT21 in a C200H or C200HS PLC rack, system integrators can exchange I/O data with a Profibus DP master, such as a Siemens SIMATIC S7 PLC, a PC-based soft PLC, or a distributed control system. This enables Omron PLCs to be integrated into mixed-vendor automation architectures, sharing real-time control signals, setpoints, and status information.

Hardware and Physical Interface

The C200HW-PRT21 is a single-slot module that plugs into any available I/O slot of the C200H backplane. It connects to the Profibus DP network via a standard 9-pin D-sub female connector on the front panel, following the Profibus pinout (pins 3 and 8 for data signals). The module includes rotary switches and DIP switches for setting the Profibus node address (0 to 99), and for configuring termination and baud rate behavior. Status LEDs on the front panel indicate power, bus communication activity, and error conditions. The module draws its power from the PLC backplane, requiring 5 V DC and 24 V DC from the main PLC power supply. The C200HW-PRT21 is equipped with a galvanically isolated bus interface to protect the PLC from electrical disturbances on the fieldbus cable.

Profibus DP Slave Operation

As a DP slave, the C200HW-PRT21 responds to cyclic data exchange requests from the DP master. The module exchanges a configured amount of input and output data with the master. The input data (from the DP master to the slave) typically represents setpoints, commands, or configuration bytes that are written to a specified area of the PLC’s memory. The output data (from the slave to the master) contains status bytes, measured values, or sensor states read from the PLC’s memory area. The C200HW-PRT21 supports up to 32 bytes of input data and 32 bytes of output data per message, which is sufficient for many I/O and control tasks. In addition to cyclic data, the module supports acyclic parameter data exchange using DPV1 functions if supported by the master.

Configuration and Integration

Configuring the C200HW-PRT21 involves two parts: setting up the hardware switches on the module and configuring the Profibus master’s network configuration tool. The hardware switches set the node address and select the data length. A GSD file (Generic Station Description) is provided by Omron and must be imported into the master’s configuration software (such as STEP 7 for Siemens or CODESYS). The GSD file describes the module’s capabilities, including the number of bytes of input and output data, supported baud rates (from 9.6 kbps to 12 Mbps), and other parameters. In the master’s configuration, the user assigns the C200HW-PRT21 to a specific station address and maps the I/O data to the master’s own I/O memory. On the Omron side, the PLC programmer uses SYSMAC programming software to allocate a data area (e.g., DM, IR) that will be automatically updated with the Profibus data exchange. The module’s own memory mapping is defined by the user.

Data Exchange and Timing

Once the network is operating, the DP master cyclically sends output data to the C200HW-PRT21 and reads input data from it. The update rate depends on the baud rate and the number of DP slaves on the network; at 12 Mbps, a small network can achieve cycle times below 1 millisecond. The module buffers the received output data and makes it available for the PLC’s CPU to read. Conversely, the PLC’s CPU writes input data into the module’s buffer, which is then transmitted to the master on the next request. The data consistency across bytes and words is ensured by the module’s internal handling. Diagnostic information, including communication errors and module status, is available both in the PLC’s status word and as alarm messages on the DP master.

Applications and Legacy Support

The C200HW-PRT21 is particularly valuable in systems where a C200H PLC must exchange data with a higher-level automation system, such as a line controller or plant SCADA, that uses Profibus as its standard fieldbus. Examples include automotive assembly lines, packaging lines with multiple machine types, and water treatment plants. Because the C200H series is a legacy platform, the C200HW-PRT21 is no longer in production but can still be found in the field. When replacing a failed unit, care must be taken to match the firmware version and hardware revision to ensure compatibility with the existing configuration. Replacement of the coin cell battery inside the module may be required for configuration retention. The GSD file version must match the module’s firmware to avoid communication issues.