Fieldbus Overview
A typical factory management control system that uses fieldbus communication can look like the figure below when it communicates with a controller.
A | Fieldbus master (SoftPLC) | B | Frame header |
C | User data to and from several virtual stations inside the Process Data Frame | D | Virtual station |
E | Controller vith multiple virtual stations |
A fieldbus master, normally a SoftPLC, exchanges information with a number of remote nodes which are called fieldbus subordinates. The master communicates with one subordinate at a time. The master transmits a frame to the subordinate and receives another frame in response.
The SoftPLC transmits data to a controller that may contain identification data, task selection information and other signals.
A controller sends responses to the SoftPLC that may contain event signals, status signals, tightening results and other signals.
The physical transmission link depends on the selected fieldbus type. A transmission consists of a Frame Header, containing address information, and a Process Data Frame, which contains all the data.
If the controller supports virtual stations, it is important to direct the correct information to each virtual station. The Process Data Frame may contain one or more Fieldbus maps, one for each virtual station.
