说明：  系统网络拓扑结构采用共享总线型，大型网络控制器NCE通过BACnet MS/TP现场总线连接下位的小型多功能DDC控制器FEC，实现数据共享和分散控制
(System network topology using a shared bus-based, large-scale network controller NCE through the BACnet MS/TP field bus to connect the next bit of small multifunctional DDC controller FEC, data sharing and distributed control)