Concept
RS-485 Communications
The information in this section provides recommendations for the RS-485 interface port configuration between the automation server and RS-485 network devices. This information is intended to supplement existing guides for the automation server and for the various RS-485 network devices.
The guidelines focus on the arrangement of the electrical interface to the RS-485 port in regard to biasing, termination, cable selection, cable length, and cable routing. There are also guidelines presented for maximum unit load (node count) and common mode voltage tolerance.
The guidelines are available through a collection of application notes. Most of the application notes target specific product families such as the b3 BACnet devices, MNB BACnet devices, Legrand power meters, and Viconics VT/VZ/SE 7xxx series devices. There is also an application note directed toward generic RS-485 network devices.
Generic RS-485 Network Devices
This application note provides recommendations and guidelines for the RS-485 interface port configuration between the automation server and generic RS-485 network devices (Modbus or MS/TP). This information is intended to supplement the instructions you receive with the various RS-485 network devices. The guidelines focus on the arrangement of the electrical interface to the automation server's RS-485 port in regards to biasing, termination, cable selection, cable lengths, and cable routing. The guidelines on maximum unit load (node count) and common mode voltage tolerance are associated with AS-P and AS-B servers.
For more information, see Generic RS-485 Network Devices .
b3 BACnet Devices
This application note provides recommendations and guidelines for the configuration of RS-485 communications between the automation server and b3 BACnet devices. This information is intended to supplement the existing configuration documents, such as the “b3 BACnet and b4920 Controller Technical Reference (30-3001-862)”. The guidelines focus on the arrangement of the electrical interface to the automation server's RS-485 port in regards to biasing, termination, cable selection, cable lengths, and cable routing. The guidelines on maximum unit load (node count) and common mode voltage tolerance are associated with AS-P and AS-B servers.
For more information, see b3 BACnet Devices .
MNB BACnet Devices
This application note provides recommendations and guidelines for the configuration of RS-485 communications between the automation server and MNB BACnet devices. This information is intended to supplement the existing configuration documents such as the “TAC I/A Series MicroNet BACnet Wiring and Networking Practices Guide (F-27360-10)”. The guidelines focus on the arrangement of the electrical interface to the automation server's RS-485 port in regards to biasing, termination, cable selection, cable lengths and cable routing. The guidelines on maximum unit load (node count) and common mode voltage tolerance are associated with AS-P and AS-B servers.
For more information, see MNB BACnet Devices .
Legrand Power Meters
This application note provides recommendations and guidelines for the configuration of RS-485 Modbus communications between the automation server and Legrand power meters. The recommendations are based on an investigation of Legrand meter models 04677, 04680, 04684, and 14669. The investigation was used to discover isolation and unit load characteristics along with requirements of the RS-485 transceiver for external failsafe biasing on the RS-485 network and to test communications operation with the meters under recommended configurations. This information is intended to supplement the product information provided with the Legrand meters. The guidelines focus on the arrangement of the electrical interface to the automation server's RS-485 port in regards to biasing, termination, cable selection, cable lengths and cable routing. The guidelines on maximum unit load (node count) and common mode voltage tolerance are associated with AS-P and AS-B servers.
For more information, see Legrand Power Meters .
Viconics VT/VZ/SE 7xxx Series Devices
This application note provides recommendations and guidelines for the configuration of RS-485 communications between the automation server and Viconics room controllers. The recommendations are associated with the Viconics VT/VZ/SE 7xxx series thermostats / room controllers configured with the Viconics plug-on MS/TP network adapter. This information is intended to supplement the instructions you receive with the various RS-485 network devices. The guidelines focus on the arrangement of the electrical interface to the automation server's RS-485 port in regards to biasing, termination, cable selection, cable lengths, and cable routing. The guidelines on maximum unit load (node count) and common mode voltage tolerance are associated with AS-P and AS-B servers.
For more information, see Viconics VT/VZ/SE 7xxx Series Devices .
Communication Port Wiring
Generic RS-485 Network Devices
b3 BACnet Devices
MNB BACnet Devices
Legrand Power Meters
Viconics VT/VZ/SE 7xxx Series Devices