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What are master and slave stations?
A master station refers to a PLC that initiates, or generates, communication messages with other PLCs, configured as slaves, over a communication network. There is typically, but not always, only one master station per network at any one time.
A slave station refers to a PLC that responds to incoming communication messages only. There can be many slave stations on any given network.
Due to the independent-operation nature of the SCADAPack PLC’s serial and Ethernet ports, each port can be designated as either a master or slave, independent of other ports on the same PLC. This means, for example, that a SCADAPack PLC, with three serial ports, can be connected to three different communication networks, configured as a master on one port and a slave on the two remaining ports.
In the following example, PLC#1 has two ports configured as masters and one configured as slave. PLCs #2 through #4 and #6 through #8 are configured with one slave port each. PLC #5 is configured with one master port. There are three independent communication networks.
