Description
The integration of serial point-to-point connections into an EtherCAT network is handled efficiently by the Beckhoff EL6021 serial interface module, which provides a high-performance communication path for RS422 and RS485 devices. Operating as a single-channel communication terminal, this unit facilitates direct, isolated connection of serial equipment to the decentralized control architecture. By executing full-duplex or half-duplex transmission via balanced differential signaling, it guarantees robust data transfer even in environments subjected to severe electromagnetic interference. The device bypasses local address configurations entirely, allowing all functional variables and protocol behaviors to be parameterized through the master PLC system.
Features
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Flexible Serial Standards: Features a selectable RS422 or RS485 hardware interface configured directly via software.
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Configurable Baud Rates: Supports multiple baud rates from 2400 to 115,200 baud for broad compatibility.
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Robust Buffer Architecture: Built-in 864-byte receive buffer and 128-byte transmit buffer prevent data loss during processing peaks.
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Galvanic Isolation: Provides 500 V electrical isolation between the internal E-bus logic and the external signal lines.
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Spring-Clamp Termination: Leverages spring-actuated terminal contacts for reliable wire connections resistant to high vibration.
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Compact Form Factor: Standard 12 mm width optimizes mounting space on high-density control panels.
Applications
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Barcode & RFID Scanner Integration: Real-time serial data streaming from logistical scanning hardware directly to the PLC.
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Industrial Weighing Systems: Connecting digital scales, load cells, and weighing terminals over isolated RS485.
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VFD & Servo Drive Control: Point-to-point RS485 network command distribution to multi-drop motor controllers.
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Environmental Sensor Networks: Collecting parameters from remote climate, pressure, and temperature transmitter arrays.
Technical Specifications
| Manufacturer |
Beckhoff |
| Model / Article Number |
EL6021 |
| Interface Standard |
1 x RS422 / RS485 |
| Data Transfer Channels |
TxD and RxD, Full / Half Duplex |
| Data Transfer Rates |
2400 to 115,200 baud (Default: 9600 baud, 8 data bits, no parity, 1 stop bit) |
| Line Impedance |
120 ohm |
| Maximum Cable Length |
Approximately 1000 m twisted pair |
| Power Supply Source |
Via E-bus (no external power contacts) |
| Current Consumption (E-bus) |
Typically 170 mA |
| Electrical Isolation |
500 V (E-bus / signal voltage) |
| Data Buffer |
864 bytes receive buffer, 128 bytes transmit buffer |
| Housing Dimensions (W x H x D) |
12 mm x 100 mm x 68 mm |
| Wire Cross-Section (Solid/Stranded) |
0.08 to 2.5 mm2 (AWG 28 to 14) |
| Wire Cross-Section (with Ferrule) |
0.14 to 1.5 mm2 (AWG 26 to 16) |
| Stripping Length |
8 to 9 mm |
| Operating Temperature |
-25 to +60 degC |
| Storage Temperature |
-40 to +85 degC |
| Relative Humidity |
95 percent, non-condensing |
| Approvals & Markings |
CE, UL, ATEX, IECEx, cFMus |
| Device Weight |
55 g |
| Country of Origin |
Germany |
| Shipping Weight (Calculated) |
0.15 kg |
| Package Dimensions (Calculated) |
150 mm x 120 mm x 45 mm |
Connections and Interfaces
| Terminal Pin |
RS422 Mode Assignment |
RS485 Mode Assignment |
| 1 |
RxD+ (Receive Data Positive) |
RxD/TxD-B (Data Positive) |
| 5 |
RxD- (Receive Data Negative) |
RxD/TxD-A (Data Negative) |
| 2 |
TxD+ (Transmit Data Positive) |
Not Used |
| 6 |
TxD- (Transmit Data Negative) |
Not Used |
| 3 |
GND (Signal Ground) |
GND (Signal Ground) |
| 7 |
Shield |
Shield |
| 4 / 8 |
Shield Connection points |
Shield Connection points |
Empirical Engineering Insights
Alternative Models & Compatibility
The module offers identical software mapping to the ES6021 version. While the EL6021 features built-in spring-tension clamp terminations, the ES6021 provides pluggable terminal blocks for accelerated physical swaps. When replacing older revisions of this module in TwinCAT, check the XML device description version compatibility to ensure correct PDO (Process Data Object) structure mapping.
Application Pitfalls & Engineering Notes
To prevent data loss over long-distance RS485 loops, the internal 120-ohm termination resistor must be active at the physical endpoints. A frequent engineering mistake is neglecting PLC cycle times; if the PLC scan rate is significantly slower than the serial incoming data block transmission time, the internal 864-byte receive buffer will overflow, causing buffer errors in the status word. Cycle your serial processing tasks concurrently with the data arrival rate.
Commissioning & Wiring Tips
Line termination for this module is configured strictly in software through the CoE (CAN over EtherCAT) directory index 0x8000. Ensure that the RS485/RS422 shielded cable is directly grounded to the DIN rail ground terminal. Unshielded serial lines running parallel to high-current variable frequency drive cabling can cause communication drops or corrupted checksum registers.
Installation Guidelines
CRITICAL WARNING: Disconnect the primary and auxiliary power supplies before initiating installation, removal, or terminal wiring. Failure to de-energize the entire control panel assembly can lead to severe electrical shock, system bus corruption, or immediate logic module damage.
1
Align the module side by side with existing EtherCAT Terminals on a standard 35 mm DIN rail. Secure utilizing the integrated double slot and key connection.
2
Lock the module firmly onto the rail until the orange latch snaps securely into place over the rail flange.
3
Strip wire insulation back 8 to 9 mm. Actuate the internal spring clamp by pressing a flat-head screwdriver into the terminal release slot.
4
Insert the stripped conductor into the round wire entry, remove the screwdriver to lock the wire in place, and verify physical terminal grip strength.