This paper presents a method to design a logic controller as an Event-Condition-Action (ECA) system, where the Modular Finite State Machine (MFSM) framework has been used to build the model for the controller. The resulting model, called an ECA MFSM, is in essence a MFSM model with a special structure that enables the processing of logic to follow the ECA paradigm. The ECA rule based method has a solid theoretical root and has been the paradigm followed to design active database systems. Copyright c 2005 IFAC