A control system includes: a master station including a PLC executing user program; and a remote station including a communication memory to which a PLC device is assigned, a slave communication unit, and a unit to or from which one or more pieces of data is input or output, and being connected to the master station through a network. The PLC transmits, to the slave communication unit, assignment object designation information designating an object that is among unit data input or output to or from the unit and to which a PLC device is assigned, and an assignment rule. The slave communication unit assigns unit data that is among unit data input or output to or from the unit and is designated by the received assignment object designation information to the communication memory based on the received assignment rule.