Industrielle styresystemer - Wiki
The task is to establish data exchange between 2 PLCs.
There are 2 main ways to exchange data: NVL and Modbus TCP.
Below are tables of advantages and disadvantages of these two methods, however, the biggest difference lies in which data transmission protocol is used.
TCP vs UDP: Differences between the protocols. The main difference between TCP (transmission control protocol) and UDP (user datagram protocol) is that TCP is a connection-based protocol and UDP is connectionless. While TCP is more reliable, it transfers data more slowly. UDP is less reliable but works more quickly.
NVL or Network Variables List
https://help.codesys.com/api-content/2/codesys/3.5.13.0/en/_cds_f_networkvariables/
Advantages | Disadvantages |
---|---|
Easy to use | Uses UDP protocol, UDP provides a simpler and less reliable form of data transmission |
Data transmission efficiency: NVL sends data in packets | Delivery is not guaranteed |
Absence of a main node: NVL does not have a binding to a main or subordinate node, making it more flexible in usage and management | Only UDP protocol or it's limited protocol support |
Optional data reading: Since data can be available to all nodes, there is no guarantee that all nodes will read or use this data |
Modbus TCP
Advantages | Disadvantages |
---|---|
Reliability: Modbus TCP protocol ensures reliable data transmission with acknowledgment of receipt | Use of master and slave in data transmission |
Wide support | Limited data transmission speed: More complex data transmission protocol. |
Delivery is guaranteed |
Since we are simulating the use of a bridge panel, we need to use TCP protocol for reliable data transmission.
PLC1 is 158.38.140.56. It will be a master.
PLC2 is 158.38.140.57. It will be a slave.
According to the task we need to transmit data of INT and BOOL types.
Kilde/Helpful links:
Configuring a Network Variable Exchange:
https://help.codesys.com/api-content/2/codesys/3.5.13.0/en/_cds_configuring_network_variables_exchange/
Modbus TCP:
https://www.prosoft-technology.com/kb/assets/intro_modbustcp.pdf