Four methods of cross-segment communication between PLCs

1. Implemented through routing mode

If two PLCs belong to different network segments and have data communication needs, the most typical application is to achieve it through routing mode. On the PLC side, you need to enable the "use router" function, fill in the corresponding gateway address, and then call the corresponding function block for communication, such as calling TSEND_C and TRCV_C in S7-1500 to achieve TCP communication; of course, there needs to be a switch that supports routing functions between the two PLCs, such as scalance xc208. The typical use of this communication architecture is shown in the figure below:

(II) Implementation through Gateway Mode

If the two PLCs belong to different network segments and there is a need for real-time communication, then you can consider the Profinet communication method and use the PN/PN Coupler gateway to achieve real-time data exchange. The PN/PN Coupler has two Profinet interfaces, each of which is linked to the respective Profinet system as a Profinet Io Device, interconnecting the two PROFINET subnets to achieve real-time data interaction. The typical usage of this communication architecture is shown in the figure below:

(III) Implementation through NAT mode

If two PLCs belong to different network segments and there is a need for data communication, NAT technology can also be used to achieve cross-segment data exchange. Two PLCs belonging to different network segments are interconnected by a device that supports NAT function, such as SCALANCE S615. The NAT device converts the address of network segment 2 to an address of network segment 1. During communication, the device in network segment 1 accesses the converted address to achieve communication between the two devices. The typical usage of this communication architecture is shown in the figure below:

Network Address Translation (NAT) is a technology for accessing a wide area network (WAN). It is a conversion technology that converts private (reserved) addresses into legal IP addresses. It is widely used in various types of Internet access methods and various types of networks. The reason is simple. NAT not only perfectly solves the problem of insufficient IP addresses, but also effectively avoids attacks from outside the network, hiding and protecting computers inside the network. The NAT function can convert IP. The specific functions are shown in the figure below:

(IV) Realization through additional communication module

If two PLCs belong to different networks, have addresses in different network segments, and have data communication requirements, you can also use the method of adding communication modules to achieve communication between the two devices. Add a communication template to one of the PLCs and give it an address in the same network segment as the second PLC. This will easily enable communication between the two devices. The typical usage of this communication architecture is shown in the figure below: