A method is described of connecting a hardware module to a fieldbus, wherein a data connection between the hardware module and the fieldbus is established by a network module which is connected to the fieldbus and which has an internal memory, said method comprising the steps that the hardware module is connected to the network module, that the communication software is read out of the memory of the network module by the hardware module, said software being provided for the communication of the hardware module with the fieldbus, that the communication software is stored in the hardware module, and that the hardware module is use to communicate over the fieldbus.