The FX2N-485-BD is Mitsubishi Electric’s RS-485 communication option board for the MELSEC FX2N compact PLC series, providing a second serial communication port via RS-485 half-duplex multi-drop interface — enabling the FX2N base unit to simultaneously communicate with SCADA systems, HMI panels, inverter drives, or Modbus RTU slave/master devices on an RS-485 bus while the built-in RS-422 port remains available for programming or HMI connection. As the most widely specified FX2N communication option board, the FX2N-485-BD is found in thousands of active FX2N installations for Modbus RTU SCADA integration, Mitsubishi FR-series inverter multi-drop control, and RS-485 network communication in facilities where RS-485 is the established serial communication medium. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the FX2N-485-BD?
The FX2N-485-BD is a communication option board that installs directly onto the FX2N base unit’s option board slot — a dedicated connector located behind the front cover of the FX2N base unit requiring no additional power supply, extension bus position, or special function module slot. The board adds an RS-485 half-duplex port with a 5-pin terminal block connector (SDA+, SDA-, SG signal ground, RDA+, RDA-), enabling connection to RS-485 multi-drop networks with up to 32 nodes (including the FX2N as one node) over cable lengths up to 500 m. The FX2N-485-BD supports Mitsubishi’s proprietary communication protocol for FX series PLCs, enabling simultaneous connection of multiple FX2N controllers on the same RS-485 bus for GX Works2 programming access and GOT HMI panel communication. The board also supports Modbus RTU slave communication, allowing any SCADA system or DCS with Modbus RTU master capability to read FX2N device data (input states, output states, data registers) directly from the RS-485 port without additional communication hardware.
Key Technical Specifications
- Model: FX2N-485-BD
- Interface: RS-485 half-duplex
- Installation: FX2N base unit option board slot (direct plug-in)
- Connector: 5-pin terminal block (SDA+, SDA-, RDA+, RDA-, SG)
- Maximum Cable Length: 500 m
- Maximum Nodes: 32 (including the FX2N)
- Baud Rate: 300 bps to 19,200 bps
- Supported Protocols: Mitsubishi FX communication protocol, Modbus RTU (slave), inverter communication (IVDR/IVRD instructions)
- Compatible FX2N base units: All FX2N models
- Power Supply: From FX2N base unit (no external supply required)
- Operating Temperature: 0°C to 55°C
- Weight: Approx. 0.05 kg
Compatibility & System Integration
The FX2N-485-BD integrates with the FX2N’s built-in communication functions without requiring additional program instructions for standard applications. For Mitsubishi inverter drive control, the FX2N-485-BD enables the IVDR (inverter write) and IVRD (inverter read) instructions to communicate with up to 8 FR-series inverters (FR-A700, FR-E700, FR-F700, FR-D700) on a single RS-485 multi-drop bus — setting speed references, reading output frequency, current, and fault codes from each drive independently using a single RS-485 cable run rather than separate analogue wiring to each drive. The FX2N-485-BD’s Modbus RTU slave mode is configured via the FX2N program’s D8120 serial communication format register and special relay M8161 (8-bit communication mode) and M8029 (communication complete flag), enabling SCADA systems with Modbus RTU masters to read and write FX2N D registers, M relays, X inputs, Y outputs, T timers, and C counters. For GOT HMI panel connection when the built-in RS-422 port is already occupied by a GX Works2 programming connection, the FX2N-485-BD’s RS-485 port can be used for GOT HMI communication using Mitsubishi’s FX RS-485 communication protocol — the GOT supports RS-485 connection to FX PLCs as a standard option. The FX2N-485-BD is also compatible with third-party Modbus RTU master devices including Schneider Vijeo SCADA, Wonderware InTouch, iFIX, and Ignition — configuring the FX2N-485-BD’s Modbus slave register map in the FX2N D register space and sharing the register map documentation with the SCADA configuration team is sufficient for complete integration.
Installation Advice
The FX2N-485-BD installs behind the FX2N base unit’s front cover — power down the FX2N before installation, slide open the front cover, align the board’s connector with the option board slot on the left side of the FX2N main board, and press firmly until the board is fully seated. The installation does not require tools in most cases, but verify the board is fully engaged by gently tugging the board after insertion — a partially inserted board causes communication failures that may be misdiagnosed as software configuration errors. For RS-485 multi-drop wiring, use shielded twisted-pair cable (120 Ω impedance, Belden 9841 or equivalent) and install 120 Ω termination resistors at both physical ends of the RS-485 bus — at the FX2N-485-BD terminal block and at the last device on the bus. Failing to terminate the RS-485 bus is the most common cause of intermittent communication errors on longer cable runs (above 50 m) or at higher baud rates (above 9,600 bps). Connect the RS-485 cable shield to earth at one end only (typically at the FX2N panel’s earth point) to prevent ground loops — an un-shielded cable or a shield grounded at both ends causes common-mode interference on the RS-485 bus that manifests as sporadic framing errors and communication timeouts, particularly in the presence of VFD switching noise. Verify that the FX2N D8120 serial communication format register is correctly configured for the intended baud rate, data bits, stop bits, and parity settings — an incorrect D8120 configuration is the most common software cause of FX2N-485-BD communication failure.
Frequently Asked Questions
Q: Can the FX2N-485-BD communicate as a Modbus RTU master (reading data from Modbus slave devices) rather than only as a slave?
A: Yes. The FX2N-485-BD supports Modbus RTU master mode via the FX2N’s RS-485 communication instructions (RS instruction for raw serial data or ADPRW instruction for Modbus master reads/writes). In master mode, the FX2N initiates Modbus read requests to slave devices (such as power meters, temperature transmitters, or other PLCs with Modbus slave interface) and writes commands to Modbus slave actuator outputs. The Modbus master and slave modes are mutually exclusive — the FX2N-485-BD operates in either master or slave mode, not both simultaneously.
Q: Can the FX2N-485-BD and the built-in RS-422 port be used simultaneously for different communication purposes?
A: Yes. The FX2N-485-BD’s RS-485 port operates completely independently from the built-in RS-422 port — the two ports can simultaneously handle different communication tasks. A typical configuration uses the built-in RS-422 port for GOT HMI communication while the FX2N-485-BD’s RS-485 port handles Modbus RTU SCADA integration or inverter multi-drop control. Both ports use the FX2N’s communication function software independently, with separate D8120 format registers for each port.
Q: Does the FX2N-485-BD support free-protocol RS-485 communication for custom serial device integration?
A: Yes. The FX2N-485-BD supports free-protocol mode via the RS instruction (RS transmit/receive), enabling custom serial communication with any RS-485 device using the FX2N program to construct and parse the serial data frames. This free-protocol mode is used for communication with devices that use proprietary serial protocols — barcode readers, weighing instruments, gas analysers, and other field instruments with RS-485 output but non-Modbus protocols. Configure D8120 for the device’s baud rate and framing, and use the RS instruction to transmit the query frame and receive the response into designated FX2N data registers.
Do you need more references from this brand? Explore our full catalog of Mitsubishi here: https://atlantechdrives.com/manufacturers/mitsubishi/
