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Decrease Building Controller CPU Usage by Offloading MS/TP Traffic

February 2015 - Connecting our economical, standalone BACnet® routers to MS/TP networks frees up the building controller's MS/TP communications which in turn provides the building controller with decreased CPU usage to be used for additional important tasks.

"Building controller CPU usage is decreased by offloading the MS/TP token passing to external BACnet MS/TP to BACnet/IP routers. This is generally important if the building controller is connected to multiple MS/TP networks," states Joe Stasiek, Sales Manager.

Standalone BACnet Routing
Routing BACnet MS/TP messages to BACnet/IP requires a standalone BACnet router or routing capability in a BACnet building controller but there are performance disadvantages when routing is accomplished in the building controller. Shifting the routing to standalone BACnet routers removes this performance demand.

Improve Building Controller Performance
Besides improving building controller performance by off-loading MS/TP traffic to a standalone router, the BACnet router offers wiring convenience. Instead of running MS/TP cable to the building controller, the installer can run MS/TP cable to the nearest Ethernet drop and install a standalone router at this location. As more IP networks are installed, there will be less need to install long MS/TP cables.

Offload JACEThe BASrouterLX - High-Performance BACnet® Router and BACnet® Multi-Network BASrouter offer the solution. Both units provide stand-alone routing between BACnet networks such as BACnet/IP, BACnet Ethernet, and BACnet MS/TP - allowing the system integrator to mix BACnet network technologies within a single BACnet inter-network. Plus, the BASrouterLX provides a high-speed processor, with advanced features that include MS/TP slave proxy support (allowing auto discovery of MS/TP slaves), MS/TP frame capture and storage for use with Wireshark®. Up to 50 BBMD entries can be made.

Reduce the Time to Configure Devices in the Field by Offloading Modbus Traffic
Although building controllers have the ability to communicate Modbus RTU over serial ports, Modbus points cannot be discovered like BACnet points requiring manual configuration of each Modbus register. "Using external Modbus RTU to our BACnet gateways, with pre-defined Modbus device profiles, makes the configuring of Modbus registers just as quick as it takes to configure BACnet points," states Joe Stasiek, Sales Manager. "The big benefit to our customers is the savings in time because using this technique greatly reduces the time to configure Modbus devices in the field."

The BASgatewayLX - Modbus to BACnet® Gateway provides a 10/100 Mbps Modbus TCP or BACnet/IP Ethernet port and an opto-isolated Modbus EIA-485 serial port for Modbus RTU or Modbus ASCII devices. Up to 30 Modbus serial devices (represented by up to 1000 polled points) can share the single Modbus port on the BASgatewayLX.

Virtual Routing
The virtual routing feature in the BASgatewayLX allows each connected Modbus device to appear as an individual BACnet compliant device, which can save configuration time if using multiple identical Modbus devices.

We Will Make Your Device Profile for You
A device profile for each Modbus type device is needed and Contemporary Controls maintains a library of common device profiles. If one is not available, we will be glad to provide it upon request. Custom device profiles can be uploaded to the BASgatewayLX. Using web pages and a resident database of common Modbus device profiles, Modbus data points from Modbus Serial or Modbus TCP devices can be mapped to BACnet objects.

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