The driver works together with all of our communication interfaces and comprises all of the functions for initializing, parameterizing, exchanging data and retrieving status information. The driver works in polling or interrupt mode and services a maximum of four cards in one PC. However, the card can be utilized as ISA, PCI or PCMCIA or a combination as desired. The functions of the device driver are independent of the fieldbus system. The access to the variables in the process image is fully identical. What is different are the parameters of the diagnostic and status structures, as well as fieldbus-specific commands. Associated definitions are included as header files. By taking these corresponding facts into account, it is possible to interchange PC cards from different fieldbus systems without this resulting in any alterations in the application. Demo programs in source code are included with the driver and thus permit quick and easy familiarization. Further components include an installation program which carries out the entire registration on the operating system.