Traditionally safety and controls systems have been strictly separated from each other. There are both benefits and liabilities in this approach. Thus, modern system employing control and safety system parts do not necessarily make a strict separation between these two elements of the system. Regardless of the degree of separation, the nodes belonging to either control or safety system may need to communicate with each other to implement the desired functionality. An increasing number of systems nowadays utilize a fieldbus to connect the distributed nodes of the system together. A time comes in the design process, when one needs to select the architecture of the physical fieldbus. That is, how and which nodes are connected? In this paper, two patterns to organize the fieldbus architecture are illustrated. In short, one either can separate the fieldbus between the safety and control system nodes or use a shared fieldbus between the nodes.