TS7
TS1
TS2
TS8
1 2 3
1
1
2
3
4
5
1 2 3
1
2
3
4
5
6
7
8
9
10
11
W1
Tx/Rx (+)
Communication Common
Tx/Rx (-)
Pin 1 of termination resistor header
W1
NC (Termination resistor Not Connected)
TERM (Termination resistor installed)
}
}
Modbus/BACnet
5
MODBUS WIRING
RS485 Wiring for Modbus
Wiring connections are made to terminal block TS2 for Modbus communication.
The Tx/Rx+ signal connects to pin 7, Tx/Rx- connects to pin 8 and communication common to
pin 9 as shown in Figure 3.1.
Termination Resistor
Connect a termination resistor across the receive/transmit signals of the last device on the
Modbus communication line. To connect the 121 ohm termination resistor on the FT2A, set
jumper W1 to the TERM position.
Disconnect the termination resistor on all other external Modbus devices. The termination
resistor of the FT2A is disconnected by setting jumper W1 to the NC (Not Connected) position.
Fig. 3.1: Modbus Wiring
i
Note: W1 jumper will either be in the NC or TERM position. It should be in the TERM
position on the last meter in the Modbus daisy chain.
RS485 Wiring: Modbus
