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Appendix E. ModBus Rerouting
E.1. Presentation
One of the nice communication features offered by
TB
OX
LT2
is the ability to act as a ModBus router.
That means that you can use a
TB
OX
LT2
to make a connection between 2 x ModBus devices that are
not on the same communication channel.
Routing can then be used to access a ModBus device through a
TB
OX
LT2
.
ModBus Protocols
This feature creates a route between communication ports configured in ModBus protocol(s):
- ModBus-RTU <--> ModBus-RTU
- ModBus-RTU <--> ModBus/TCP
Concerning TCP/IP protocols, other redirections are possible using IP forwarding, NAT and
Virtual Server (see Appendix F.).
Routing 2 communication ports in ModBus/TCP, is called IP forwarding (see next chapter).
Communication principle
The idea is that
TB
OX
LT2
receiving frames, analyzes the Station address: if it is for its own use, it keeps
the frames; otherwise they are pushed to the “routed” communication port.
E.2. Routing using TWinSoft
ModBus rerouting allows associating two ‘ModBus-RTU’ communication ports, in order to access a
remote RTU with TWinSoft from your computer by rerouting through a ‘Master’ RTU.
The typical application is dialing an RTU to access a remote RTU connected to the RS485 network.
You access routing from the main menu of
TWinSoft : Communication

Routing