VIPA System 200V IM Series, Manual

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Chapter 8 Ethernet coupler
Manual VIPA System 200V
8-6 HB97E - IM - Rev. 06/29
MAC/DLL IP TCP API
Layer 2 Layer 3 Layer 4 Layer 7
14 Byte 20 Byte 20 Byte Length depends on protocol
...
Port 502 ModbusTCP-Header Modbus User data
6 Byte
...
max.254 Byte
ModbusTCP
Port 7779/7780 Siemens S5 Header User data
16 Byte
...
max.64kByte
Siemens S5
ModbusTCP is a Modbus-RTU protocol, put upon TCP/IP.
The Modbus protocol is a communication protocol supporting a hierarchic
structure with one master and several slaves. ModbusTCP extends
Modbus to a client server communication where several client may access
a server.
For the addressing happens by means of the IP addresses, the address
integrated in the Modbus telegram irrelevant. Furthermore, the check sum
is not required because the sequence insurance happens via TCP/IP.
After the request of a client, this awaits the answer of the server for a
configurable time.
ModbusTCP exclusively uses the RTU format.
Every Byte is transferred as one sign. This enables a higher data pass-
through than the Modbus-ASCII format. The RTU time supervision is
omitted for the header contains the size of the telegram length to be
received.
Data that are transferred via ModbusTCP may contain bit and word
information. At bit chains, the highest bit is send first, i.e. in a word it is at
the most left position. At words, the highest Byte is send first.
The access to a Modbus slave happens via function codes that are
described in detail in this chapter further below.
The Siemens S5 Header protocol serves the data transfer between PLC
systems. Deploying the organization format (short ORG) integrated in the
Siemens S5 Header protocol, a short description of a data source res. data
destination in PLC environment is possible.
The possible ORG formats are corresponding to Siemens.
API structure
ModbusTCP
Siemens S5
Header