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VACON® 1000 Fieldbus Options
Operating Guide
Each Modbus message has the same structure. Four basic elements are present in each message. The sequence of these elements is
the same for all messages, to make it easy to parse the content of the Modbus message. In the Modbus network, the master always
starts the conversation. A Modbus master sends a message and depending on the contents of the message, a slave reacts to it.
There can be more masters in a Modbus network. Addressing in the message header is used to define which device must respond
to a message. If the address field does not match their own address, all other nodes on the Modbus network ignore the message.
VACON® 1000 is equipped with Modbus RTU support as standard. In case, there are problems related to Modbus, contact Danfoss
Drives. Provide a description of the problem and the Drive Info File.
Modbus TCP
Modbus
RTU master
Modbus RTU
Illustration 2: Principal Example Diagram of Modbus
2.3 PROFIBUS DP
PROFIBUS (process fieldbus) is a standard for fieldbus communication in automation technology. PROFIBUS DP (Decentralized Pe-
ripherals) is a protocol made for (deterministic) communication between PROFIBUS masters and their remote I/O slaves, such as
sensors or actuators in production automation applications.
PROFIBUS DP is standardized under IEC 61158 and IEC 61784, which guarantees compatibility with devices from various manufac-
turers.
The PROFIBUS protocol implements 3 of the 7 layers defined in the OSI layer model (Open Systems Interconnection Reference Mod-
el).
•
Layer 1 defines the physical transmission. The physical layer for PROFIBUS DP is RS485.
•
Layer 2 defines the description of the bus access method. With PROFIBUS, this is the master/slave method with the token meth-
od.
•
Layer 7 forms the interface to the application and shows the link between the application and communication. With PROFIBUS,
the communication protocol PROFIBUS DP-V0 is used here.
2.4 CANopen
The CAN (controller area network) fieldbus only defines the physical layer and the data-link layer of a network. See the ISO 11898
standard for information. The CAN fieldbus does not define the application layer. In practice, the hardware contains the physical
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