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Modbus ISO/OSI Model
Supported Information Types
Implemented Protocol Stacks
Applicable Products
References
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-IDA
group 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/a | TCP (RFC 793) | | 3 |
Network Layer |
n/a | IP (RFC 791) | | 2 |
Link Layer |
n/a | IP (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
Applicable Products
 | ipConvLite | inexpensive protocol converter for standardized application
start price 2.500,- €
Details...
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 | ipConvOPC | Softwarepackage for conversion between OPC DA 2.05 Server and standard protocols
Details...
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 | ipConvPS | Universal protocol converter with integrated Profibus-DP, Slave interface
Details...
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| ipConvPM | Universal protocol converter with integrated Profibus-DP, Master interface
Details...
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 | ipConv | Universal protocol converter for highest degree of flexibility
Details...
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References
 | Storebælt, Denmark
Details...
| Denmark | ipConv | IEC 60870-5-104, Master / IEC 60870-5-104, Slave / Simatic TDC, Master / Modbus TCP/IP, Master / |
 | ELIA
Details...
| Belgium | ipConv | 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 / |
 | Mainova Communication Hub
Details...
| Germany | ipConv | OPC DAXML 1.01 Server / IEC 60870-5-104, Slave / IEC 60870-5-101, Master / Modbus, Master / SEAB 1F, Master / |
 | Neptune RTS, USA
Details...
| USA | ipConv | DNP V3.00, Slave / Simatic TDC, Master / Modbus, Master / CDC Type I, Slave / |
 | Metro Istanbul
Details...
| Turkey | ipConvLite | Modbus, Master / IEC 60870-5-104, Slave / |
 | PEMEX, Madero
Details...
| Mexico | ipConv | DNP V3.00, Slave / Harris-5000/6000, Slave / Modbus, Master / |
 | BritNed, Great Britain / Netherlands
Details...
| Great Britain | ipConv | IEC 60870-5-104, Slave / Simatic TDC, Master / Modbus TCP/IP, Master / |
 | ISKI
Details...
| Turkey | ipConv | Indactic 33/41, 2033, Slave / Modbus, Master / |
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