Data highway DH configurations

Communication within a DCCS is implemented by means of the system bus or data highway along which data are exchanged between elements of the system at the same or at different hierarchical levels. The bus represents the basic system interface and should provide the following features 50  

The system architecture is a major factor in determining the capacity/constraints of a DCCS and this will be substantially affected by the type of data highway employed and the way in which it is configured. Various DH configurations are illustrated in Fig. 7.107. 

A more recent development is to employ Local Area Networks (LANs) where the LAN is a serial communication link used as a data highway in the DCCS for the integration of intelligent terminals at the higher hierarchical levels. There are two principal types of LAN applicable to DCCS, viz.  

An important aspect of the DH is the highway protocol which is a set of rules which define the format, timing, priority, and control of the transmission and exchange of data on the DH. The performance of the DH depends to a very large extent upon the protocol employed. If the protocol is poorly designed then the DH will almost certainly jam with data and fail. 

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