• The Modbus protocol was originally developed and published by Modicon at the beginning of the 80ies. The standard is primarily used in process automation. Because of its openness and simplicity, it has become a de-facto industry standard. The Modbus Organization has taken care of its further development and updates, it also provides all protocol-related documentation.

    Modbus supports two different transmission modes:

    • Modbus serial
      supports communication via serial interfaces such as RS232, RS485
    • Modbus TCP/IP
      supports communication based on TCP/IP technologies

    Modbus serial supports two different transmission modes:

    • Modbus RTU
      uses binary data encoding
    • Modbus ASCII
      uses ASCII code for encoding data in readable character strings

    Today, only Modbus RTU communication is still in practical use.

    Modbus applies the master/slave principle, where one master can communicate with one or several slaves. A slave can only respond to explicit requests (polls) by the master.

    Modbus supports only binary and 16-bit values, which are read in blocks by the master, neither quality identifiers nor time stamps can be used.

7 Application Layer Modbus Application Layer
6 Presentation Layer n/a
5 Session Layer n/a
4 Transport Layer n/aTCP (RFC 793)
3 Network Layer n/aIP (RFC 791)
2 Link Layer n/aIP (RFC 791)
1 Physical Layer RTU (binary encoding)
ASCII (ASCII encoding)
RS232 (V.24), RS485
Ethernet (IEEE 802.3)
Supported Information Types
Control Direction
  • Single Command
  • Digital setpoint [16 bit]
Monitoring Direction
  • Single indication [1 Bit]
  • Measured value [16 bit]
Available Protocol Stacks

Modbus, Master

Modbus, Slave

Modbus TCP/IP, Master

Modbus TCP/IP, Slave

Applicable Products
  • ipConvLite

    Universal protocol converter for small and distributed applications

  • ipConvOPC

    Windows software package for universal conversion between diverse standard protocols

  • ipConv/VM

    Universal protocol conversion for VMware Workstation and VMware ESXi

  • ipConv/Cloud

    Universal protocol conversion for the cloud environment or Linux based edge devices

  • ipConvLite/MEC2PBS

    Universal protocol converter with integrated PROFIBUS-DP, slave interface

  • ipConvLite/MEC2PBM

    Universal protocol converter with integrated PROFIBUS-DP, master interface

  • ipConvLite/MEC2PNS

    Universal protocol converter with integrated PROFINET-IO, slave interface

  • ipConv

    Universal protocol converter for highest degree of flexibility

  • ip4Cloud

    Link critical processes securely to IT/Cloud/SCADA services

  • ip4Cloud/SEC3PB

    Capture PROFIBUS data by eavesdropping and transmit it to Cloud/IT or SCADA services

  • ip4Cloud/SEC3IO

    Switch and monitor digital I/O states to transmit them to IT/Cloud/SCADA services

  • ipELB

    4-Port Ethernet Line Breaker with relay controlled Ethernet ports and integrated I/O module

  • ELIA
    ELIA, Belgium

    Products: ipConv
    Protocol Stacks: Modbus TCP/IP, Master IEC 60870-5-104, Slave Telegyr 065, Master Telegyr 102, Master Telegyr 809, Master Tracec 32, 62, 92, 92P, 122, 130 & 142 Master

  • Storebælt
    Storebælt, Denmark

    Products: ipConv
    Protocol Stacks: IEC 60870-5-104, Master IEC 60870-5-104, Slave Simatic TDC, Master Modbus TCP/IP, Master

  • Power Plant Boxberg
    Power Plant Boxberg, Germany

    Products: ipConvLite ipConvPM
    Protocol Stacks: IEC 60870-5-104, Slave IEC 60870-5-104, Master Modbus, Slave Profibus-DP, Master

  • Metro Istanbul
    Metro Istanbul, Turkey

    Products: ipConvLite
    Protocol Stacks: Modbus, Master IEC 60870-5-104, Slave

  • Nordsee One
    Nordsee One, Germany

    Products: ipConv
    Protocol Stacks: Modbus, Master IEC 60870-5-104, Slave IEC 60870-5-101, Slave IEC 61850, Client IEC 61850, Server OPC UA 1.02, Server SNMP, Client

  • DUBAL21
    DUBAL21, United Arab Emirates

    Products: ipConvLite
    Protocol Stacks: DNP V3.00, Slave Modbus TCP/IP, Master

  • PEMEX, Madero
    PEMEX, Madero, Mexico

    Products: ipConv
    Protocol Stacks: DNP V3.00, Slave Harris-5000/6000, Slave Modbus, Master

  • ISKI
    ISKI, Turkey

    Products: ipConv
    Protocol Stacks: Indactic 33/41, 2033, Slave Modbus, Master

  • Communication Node for TASE.2, ELCOM-90
    Communication Node for TASE.2, ELCOM-90, Germany

    Products: ipConv
    Protocol Stacks: IEC 60870-5-104, Slave TASE.2, Server Modbus, Slave ELCOM-90 Responder, Server