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Modbus

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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.

ISO/OSI Model

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]

Implemented Protocol Stacks

Modbus, MasterModbus, Slave
Modbus TCP/IP, MasterModbus TCP/IP, Slave

Applicable Products

ipConvLiteipConvLiteinexpensive protocol converter for standardized application
start price 1.800,- €
Details...
product/ipConvLite/en/ipConvLite_EN.pdf
ipConvOPCipConvOPCSoftwarepackage for conversion between OPC DA 3.0 Server and standard protocols
Details...
ipConvPBSipConvPBSUniversal protocol converter with integrated PROFIBUS-DP, slave interface
Details...
ipConvPBMipConvPBMUniversal protocol converter with integrated PROFIBUS-DP, master interface
Details...
ipConvPNMipConvPNMUniversal protocol converter with integrated PROFINET-IO, master interface
Available soon !
Details...
ipConvPNSipConvPNSUniversal protocol converter with integrated PROFINET-IO, slave interface
Details...
ipConvipConvUniversal protocol converter for highest degree of flexibility
Details...
product/ipConv/en/ipConv_en.pdf

References

ELIAELIA
Details...
BelgiumipConv 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, DenmarkStorebælt, Denmark
Details...
DenmarkipConv IEC 60870-5-104, Master / IEC 60870-5-104, Slave / Simatic TDC, Master / Modbus TCP/IP, Master /
HVDC New ZealandHVDC New Zealand
Details...
New ZealandipConv ipConvLite DNP V3.00, Slave / DNP V3.00, Master / TASE.2, Server / TASE.2, Client / Modbus, Master / Simatic TDC, Master /
Mainova Communication HubMainova Communication Hub
Details...
GermanyipConv OPC DAXML 1.01, Server / IEC 60870-5-104, Slave / IEC 60870-5-101, Master / Modbus, Master / SEAB 1F, Master /
Power Plant BoxbergPower Plant Boxberg
Details...
GermanyipConvLite ipConvPM IEC 60870-5-104, Slave / IEC 60870-5-104, Master / Modbus, Slave / Profibus-DP, Master /
Neptune RTS, USANeptune RTS, USA
Details...
USAipConv DNP V3.00, Slave / Simatic TDC, Master / Modbus, Master / CDC Type I, Slave /
Metro IstanbulMetro Istanbul
Details...
TurkeyipConvLite Modbus, Master / IEC 60870-5-104, Slave /
Nordsee OneNordsee One
Details...
GermanyipConv 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 /
DUBAL21DUBAL21
Details...
United Arab EmiratesipConvLite DNP V3.00, Slave / Modbus TCP/IP, Master /
PEMEX, MaderoPEMEX, Madero
Details...
MexicoipConv DNP V3.00, Slave / Harris-5000/6000, Slave / Modbus, Master /
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