Design of distributed computer control systems

If the DCCS is required to replace an existing control system (i.e. if the plant is being retrofitted) then the microcontrollers will normally be located in the central control room (CCR). In this case, the distribution features of the DCCS will not be fully utilised and the significance of the digital data highway (DH) will also be reduced. 

In an entirely new plant, however, various DCCS components will be housed in local control rooms (LCR) or in outstations. The primary operator stations (OS) and 

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