Network Connections; Rs485 Interface Characteristics; Connector Pinout; Terminating Resistor - WEG bacnet CFW701 User Manual

3 NETWORK CONNECTIONS

The CFW701 frequency inverter has a standard RS485 interface. Information about the connection and
installation of the inverter to the network is presented below.
3.1 RS485
3.1.1

RS485 Interface Characteristics

The interface follows the EIA-485 standard.

It operates as a slave in the Modbus RTU, BACnet and N2 network.

It allows communication baud rates from 9600 up to 57600 Kbit/s.

The interface is electrically isolated and with differential signal, which grants more robustness against

electromagnetic interference.
It allows the connection of up to 32 devices to the same segment. More devices can be connected by using

repeaters 1 .
A maximum bus length of 1000 meters.

3.1.2

Connector pinout

The RS485 interface is available at the XC1 connector with the following connections:
3.1.3

Terminating resistor

It is necessary to enable a terminating resistor at both ends of the main bus for each segment of the RS485
network. There are switches in the CFW701 frequency inverter that can be activated (by placing both switches
S2 to ON) to enable the terminating resistor.
3.1.4

Connection with the RS485 Network

The following points must be observed for the connection of the device using the RS485 interface:
It is recommended the use of a shielded cable with a twisted pair of wires.

It is also recommended that the cable has one more wire for the connection of the reference signal (GND).

In case the cable does not have the additional wire, then the GND signal must be left disconnected.
The cable must be laid separately (and far away if possible) from the power cables.

All the network devices must be properly grounded, preferably at the same ground connection. The cable

shield must also be grounded.
1 The limit number of devices that can be connected to the network depends also on the used protocol.
Table 3.1: RS485 connector pinout
Pin Name Function
10 A-Line (-) RxD/TxD negative
9 B-Line (+) RxD/TxD positive
8 GND 0V isolated from the RS485 circuit
Figure 3.1: Terminating Resistor and RS485 connector
NETWORK CONNECTIONS
CFW701 | 11