Server redundant computer configurations that use the Modbus RTU Communications option must be configured as in the following diagram:
The programmable controller needs to respond through both of its serial cards at the same slave address at the same time. However, the slave node is only heart beating. It is not reading the full data set. The master node reads the full data set.
Important: Because both RTU cards have the same ID they have to be in separate networks.
Supported communication interfaces.