Modbus TCP to Modbus RTU and/or Modbus ASCII Gateway

  The DCB Ether-Modbus gateway allows serial Modbus RTUs to communicate and interoperate with Modbus/TCP based controllers. Modbus has been extended to operate over Ethernet using the IP protocol suite. This gateway converts between the Modbus TCP/IP protocol and Modbus ASCII/RTU protocols transparently. The EMB-02 enables one or more MODBUS controllers to communicate with modbus ASCII/RTU based serial RTUs but it will not allow Modbus/TCP RTUs to operate with a serial MODBUS controller.

   DCB's EMB-02 Modbus/TCP to
Two serial ports that each support RS-232 - RS-422 - RS-485 2/4 wire

EMB-02 Modbus/TCP to Modbus RTU and or Modbus ASCII Gateway

  • Configuration via Browser, telnet or serial port
  • Enable serial Modbus devices to communicate with a Modbus/TCP host computer
  • SNMP agent functionality
  • Protocol aware... minimum configuration needed
  • Two serial ports that each support RS-232, RS-422, RS-485 2 or 4 wire
  • 10 or 100 Mbps Ethernet
  • RS-232 interface speeds to 230 Kbps
  • RS-485 Bus mastering for two independent poll strings
  • DIN Rail or wall mounting
  • 9 to 36 volts DC and or 115VAC (other power options are available)


The EtherModbus gateway contains two independent serial ports. Each may be configured as RS-232, RS-422, or RS-485 (2 or 4 wire). When configured for RS-485 4-wire, multiple RTU polling strings may be polled on each interface.

For other applications (point-to-point direct RS-232 links or Point-to-multiple point dialed links ) see the EtherPath single port serial server. The EtherPath uses TCP/IP.

A companion product, the EtherPoll is appropriate for applications using other protocols. The EtherPoll is protocol independent, and requires no knowledge of the RTU protocol. This allows it to work with any asynchronous byte-oriented protocol with no additional configuration. The EtherPoll uses UDP/IP. It's data sheet is here.

The EtherGate is another companion product that is protocol-aware. It enables serial SCADA devices to communicate via an Ethernet network. The EtherGate is ideal for transporting SCADA protocols via Ethernet. To transport SCADA protocols over Frame Relay circuits (without ethernet), use the DCB BPF Scada-FRAD.

General Specs


Four LEDs indicate LAN and port status


Data Port


  • Two serial ports, DE-9 (commonly known as a DB-9 PC connector) DTE interface, individually configurable
  • RS-485 two or for wire interfaces (with bus-mastering on the 4-wire)
  • Serial speeds from 300 bps to 230,000 bps

    LAN Connection

    Interface: 10/100BaseT auto-selected



    Front view of DCB EMB-02


    see user manual

    part number

    EMB-02 EtherModbus; Dual Port Modbus/TCP to serial Modbus gateway


    Related pages

    see other pages



    301-924-7400 EXT 25

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