Modbus remains a popular network interface and is commonly found on jobs such as boiler control, variable speed drives, and metering applications, but these devices lack BACnet compliance. To make Modbus devices appear as individual BACnet devices, a BASgatewaySX is used. The BASgatewaySX has one 10/100 Mbps Ethernet port for Modbus TCP and BACnet/IP and an opto-isolated Modbus EIA-485 serial port for Modbus RTU or Modbus ASCII devices.
Up to 200 Modbus serial devices represented by up to 2,000 polled points can share the single Modbus EIA-485 port on the BASgatewaySX. BACnet COV notification is supported on 200 points (100 Analog and 100 Binary points). The virtual routing feature in the BASgatewaySX allows each connected Modbus device to appear as an individual BACnet compliant device.
A device profile is needed for each Modbus type device. Contemporary Controls maintains a library of freely-available device profiles available for download. If the device profile is not available, Contemporary Controls will provide it upon request. Custom Modbus device profiles can also be uploaded to the BASgatewaySX using a web page.
Using HTTPS webpages 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.
The BASgatewaySX is housed in a metal case available as 35-mm DIN-rail mount (BASGSX-M1) or Panel mount (BASGSX-M1/P) model. Powered from a 24 VAC/VDC (± 10%) source, its half-wave rectified power supply allows sharing of power with other half-wave devices.The optically-isolated serial port allows for connection to either 2-wire or 3-wire EIA-485 networks using a removable 5-pin terminal block. Up to 200 EIA-485 Modbus serial devices represented by up to 2,000 polled points can share the serial bus at data rates between 2.4 and 115.2 kbps. External DIP switches allow flexible bias and termination options. They can be removed for mid-span installations.The Ethernet port offers a shielded RJ-45 connector. Through auto-negotiation and Auto-MDIX, it automatically matches connections to the attached equipment. Therefore, either CAT5 straight-through or crossover cable can be used to attach to the BACnet/IP or Modbus TCP network at either 10 or 100 Mbps speed.A resident web server allows for commissioning, and troubleshooting via a standard web browser. A reset switch is provided for returning to the factory default IP address. LED indicators provide communication status on both the Ethernet and serial ports.
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