Beckhoff EL5042 EtherCAT Encoder Terminal

The Beckhoff EL5042 is a high-performance EtherCAT terminal designed for interfacing with absolute encoders using the BiSS-C (unidirectional) or Synchronous Serial Interface (SSI) protocols. This two-channel encoder interface module is a critical component for high-precision motion control and positioning applications. The EL5042 acts as a master, transmitting clock signals to the encoder and receiving position data, including both singleturn and multiturn values, along with status and error information. Its compact 12 mm width and support for distributed clocks make it a space-efficient solution for multi-axis motion systems in Beckhoff automation architectures.

Technical Specifications

The EL5042 features two independent encoder channels. Encoder supply voltage is either 5 V (using an external supply via the optional ZK1090 cable) or 9 V (generated internally from the power contacts). The total current available for both encoders is 0.5 A. The terminal supports unidirectional BiSS-C protocol, where data transmission is triggered by the master clock, and standard SSI protocol for compatibility with a wide range of absolute encoders. Data transmission is clocked by the EtherCAT master, with timeout detection for end-of-data transmission. Communication with the EtherCAT system is via the E-bus interface. The terminal includes status LEDs for each channel and integrated diagnostics. The EL5042 is designed for use with the EK1100 or EK1501 EtherCAT couplers. Operating temperature range is 0°C to 55°C, with storage from -25°C to 85°C. Protection rating is IP20. Dimensions are 12 mm (width) × 100 mm (height) × 68 mm (depth). The terminal mounts on a 35 mm DIN rail.

Key Features

• 2 independent encoder channels for BiSS-C (unidirectional) or SSI communication

• Supports singleturn and multiturn absolute encoders

• BiSS-C master function with clock-triggered data transmission

• SSI protocol compatibility with standard encoders

• Selectable encoder supply voltage: 5 V (external) or 9 V (internal)

• Total encoder supply current of 0.5 A for both channels

• Timeout detection for end of data transmission

• Compatible with Beckhoff ZK1090 series cable sets

• Integrated status LEDs per channel

• Configuration via CoE (CANopen over EtherCAT)

BiSS-C and SSI Protocol Support

The EL5042 supports the unidirectional BiSS-C protocol, which is a high-speed serial interface commonly used with absolute encoders in advanced motion control systems. Data transmission is triggered by the master clock generated by the EL5042. The end of data transmission is identified using a timeout detection mechanism. This protocol enables reading of singleturn position (position within one revolution), multiturn position (number of revolutions), and encoder status bits. The module also supports the widely adopted SSI protocol, ensuring compatibility with many legacy and new absolute encoders. The EL5042 can be configured via CoE objects to match the encoder's data format, including number of data bits, code type (binary or Gray), baud rate, and sampling rate. Supported baud rates are determined by the encoder requirements and the EtherCAT cycle time, enabling flexible adaptation to specific encoder models.

Integration with EtherCAT and TwinCAT

The EL5042 integrates seamlessly into the Beckhoff EtherCAT system. It supports distributed clocks, enabling precise synchronization of position data with the EtherCAT cycle. Configuration is performed in the TwinCAT engineering environment, which automatically detects the terminal and assigns process data objects. Users select the encoder type (SSI or BiSS-C) and configure data format parameters, and the EL5042 then reads the position value, presenting it as a 32-bit integer in the process image. Diagnostic information, including encoder error and data validity, is also available. TwinCAT 3 provides function blocks for encoder communication, simplifying the process of reading position data and status information in user programs. The terminal can be installed anywhere within an EtherCAT terminal strand, allowing flexible positioning near the encoders to minimize cable runs.

Applications

The EL5042 is used in applications requiring absolute position feedback with high precision, including machine tools (spindle and feed axes), robotic systems (joint angle feedback), linear and rotary positioning stages, packaging machinery (cut-to-length registration), printing presses (paper tension control and registration), and other automated systems where absolute position data is critical for safe and accurate operation. The SSI support allows connection of cost-effective SSI encoders, while BiSS-C support provides high-speed, high-resolution feedback for advanced motion control. The two-channel configuration enables a single terminal to serve two axes, reducing hardware cost and panel space. Common industries served include automotive manufacturing, electronics assembly, medical device production, and general industrial automation.

Wiring and Installation

Install the EL5042 in an EtherCAT terminal strand by attaching it to the right side of an EtherCAT coupler (such as the EK1100) or to an existing terminal. The double slot and key connection system ensures secure side-by-side mounting. Connect the BiSS-C or SSI encoder to the terminals using Beckhoff ZK1090 series cables or custom wiring. The pinout for encoder connection includes Data+, Data-, Clock+, Clock- for BiSS-C and differential SSI. For single-ended SSI signals, appropriate wiring adaptations may be required. The EL5042 provides encoder power on the terminals (5 V or 9 V). The terminal automatically detects the presence of encoders and signals any wiring errors via the status LEDs. The module must be installed in a control cabinet with adequate clearance for heat dissipation. Shielded twisted-pair cables are recommended for encoder connections, particularly when cable lengths exceed 10 meters.

Conclusion

The Beckhoff EL5042 EtherCAT terminal provides a compact, high-performance interface for BiSS-C and SSI absolute encoders. Its two independent channels, flexible encoder supply options, and seamless integration into the EtherCAT system make it an excellent choice for precision position feedback in motion control applications. The terminal's support for both industrial protocols and its comprehensive diagnostic capabilities ensure reliable and accurate encoder data acquisition for a wide range of industrial automation tasks.