Siemens PLC User Manual
PLC to PLC
Communications
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Unrestricted © Siemens 2020
Page 2
Agenda
- PUT/GET S7 Communications
- Modbus/TCP
- Open User communications
- I-Device
- OPC UA
- Flexible F-Link
- Libraries
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PUT/GET
Advantages
• Single sided – only needs to be programed in one PLC
• Works in all Simatic PLC’s
• Independent of the communication media
• Can be used on all S7 data areas
• Wizard is available for setup in TIA
Disadvantages
• No security
• Blocked by default on the S7-1200 and S7-1500
• Data blocks have to be unoptimised
• Only small amounts of data can be transferred <160bytes
• No acknowledgement of transfer this needs to be
engineered if needed
• Always takes a connection resource
https://support.industry.siemens.com/cs/au/en/view/82212115
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Modbus/TCP
Great for communication to 3rdparty devices but can be used for PLC to PLC communications
https://support.industry.siemens.com/cs/au/en/view/102020340
Advantages
• Cross vendor communication
• Built in diagnostic
• Routable over Ethernet
• Optimized Data blocks are supported
• Defined communications timeout
Disadvantages
• No security or encryption
• No setup wizard
• Server/Client blocks must be programmed
Unrestricted © Siemens 2020
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Open User Communications
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TCP, ISO on TCP or UDP
TCP
ISO on TCP
UDP
Speed
Rapid
Rapid
Very Rapid
Quantity
Medium to Large
S7
-1500: 64kB
S7
-1200: 8kB
S7
-300/400: 32kB
Medium to Large
Same as TCP
Small to Medium
S7
-1500: 2kB
Others: 1472B
Connection
Connection
orientated
Connection
orientated
Connectionless
Acknowledgment
Acknowledgment of
sending and receiving
of data
Acknowledgment of
sending and
receiving of data
Only Acknowledges
sending and not
that it was received
Systems
Siemens and 3
rd
Party
Siemens
Siemens and 3
rd
Party
https://support.industry.siemens.com/cs/au/en/view/26171811
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