Watlow F4T Install & Troubleshooting   •  24  •  Chapter 2 Install and Wire 
Communications Connections
EIA-232/485 Modbus RTU Communications
485 common
485 T+/R+
CB
CA
CC
CB
CA
C5
C3
C2
485 T-/R-
485 T+/R+
485 T-/R-
232 common
to DB9 pin 2 (RD)
to DB9 pin 3 (TX)
•  Wire T-/R- to the A terminal 
of the EIA-485 port.
•  Wire T+/R+ to the B terminal 
of the EIA-485 port.
•  Wire common to the common 
terminal of the EIA-485 port.
•  Do not route network wires 
with power wires. Connect 
network wires in daisy-chain 
fashion when connecting 
multiple devices in a net-
work.
•  A termination resistor may be 
required. Place a 120 Ω resis-
tor across T+/R+ and T-/R- of 
last controller on network.
•  Do not wire to both the EIA-
485 and the EIA-232 pins at 
the same time.
•  Two EIA-485 terminals of 
T/R are provided to assist in 
daisy-chain wiring.
•  Do not connect more than 
one controller on an EIA-232 
network.
•  Do not connect more than 16  
controllers on a Standard Bus 
EIA-485 network.
•  Maximum number of control-
lers on a Modbus network is 
247.
•  Maximum EIA-232 network 
length: 15 meters (50 feet)
•  Maximum EIA-485 network 
length: 1,200 meters (4,000 
feet)
•  1/8th unit load on EIA-485 
bus.
Modbus-IDA 
Terminal
EIA/TIA-485 
Name
Watlow Terminal 
Label
Function
DO A CA or CD T-/R-
D1 B CB or CE T+/R+
common common CC or CF common
Note:
:
This module must be placed in slot 6.
Anderson-Bolds ~ 216-360-9800