2.8 Protocol Integration
2.8 Protocol Integration
In this lesson: you will be able to expose controllers to a BAS/SCADA over BACnet/IP, BACnet/SC, and Modbus TCP, and understand device instances, object mapping, and virtual networks.
Three protocol adapters
The gateway's other job is to make legacy Network 8000 data readable by a modern building management system. It does that with three protocol adapters — BACnet/IP, BACnet/SC, and Modbus TCP — which you start and configure from the Protocols page. Each is independent: turn on the ones the site needs.
BACnet/IP
BACnet/IP is the common one. The gateway presents your controllers to the BACnet network. Each controller becomes a virtual BACnet device, and its points become standard BACnet objects — analog inputs for sensors, analog outputs for setpoints, binary inputs and outputs for the digital points. You set a device instance number for the gateway and a UDP port (the BACnet default is 47808). A head-end can then discover the gateway, browse each virtual device, and read or write points.
Two things to get right: instance numbers must be unique across the whole BACnet internetwork — a clashing device instance is the classic “why can't I see it” fault. And if the gateway routes its virtual devices onto their own virtual network number, that number must not collide with a real network already on the site. Plan your instances and network numbers with the BAS owner before you go live.
BACnet/SC
BACnet/SC — Secure Connect — is the modern, encrypted, WebSocket-based flavour of BACnet. Instead of broadcasting on the local subnet, the gateway makes an outbound TLS connection to a hub. You configure the hub URL and the certificates. Use BACnet/SC where the network is routed, secured, or across sites, and where plain BACnet/IP broadcast will not reach — it is the direction the industry is heading.
Modbus TCP
Modbus TCP is the SCADA-friendly option. The gateway serves controller data as Modbus registers — input registers and holding registers for the analog values, discrete inputs and coils for the digital values — laid out in a fixed per-controller map. You set the port (the Modbus default is 502, and note that low ports need elevated privilege, so a non-privileged port is sometimes used). One gotcha to teach every SCADA integrator: analog values are scaled — read a register and divide, write and multiply — so a value like 72.5 appears as 725.
Security posture
Whichever protocols you enable, the security posture is the same: these are network services, so restrict them by firewall to the BAS network, bind to a specific interface rather than everything, and require authentication to start or stop them. Expose data to the systems that need it — and nothing more.
Key points
- Three independent adapters, started from the Protocols page: BACnet/IP, BACnet/SC, Modbus TCP.
- In BACnet, each controller becomes a virtual device; points become AI/AO/BI/BO objects. Device instances must be unique across the internetwork.
- A virtual network number must not collide with a real network on site.
- BACnet/SC is an outbound encrypted WebSocket to a hub (TLS) rather than local UDP broadcast.
- Modbus analog values are scaled by 10 (72.5 reads as 725); divide to read, multiply to write. Firewall and authenticate all adapters.
Check your understanding
- Name the three protocol adapters the gateway provides.
- In BACnet, each controller is presented as what, and its points as what?
- What must be unique across the BACnet internetwork, and what network-number mistake causes conflicts?
- How does BACnet/SC differ from BACnet/IP in how it connects?
- A SCADA integrator reads a Modbus register and gets 725 for a 72.5°F sensor. What is happening?