Watlow Ez-Zone PM8 - Modbus RTU or Standard Bus EIA-485 Communications; Standard Bus EIA-485 Communications; Wiring a Serial EIA-485 Network

Watlow EZ-ZONE
®
PM PID Controller • 21 • Chapter 2 Install and Wire
Óç
Warning:
Use National Electric (NEC)
or other country-specific
standard wiring and safety
practices when wiring and
connecting this controller to
a power source and to elec-
trical sensors or peripheral
devices. Failure to do so may
result in damage to equip-
ment and property, and/or
injury or loss of life.
Note:
Maximum wire size termina-
tion and torque rating:
• 0.0507 to 3.30 mm
2
(30 to
12 AWG) single-wire termi-
nation or two 1.31 mm
2
(16
AWG)
• 0.8 Nm (7.0 lb.-in.) torque
Note:
Adjacent terminals may be
labeled differently, depend-
ing on the model number.
Note:
To prevent damage to the
controller, do not connect
wires to unused terminals.
Note:
Maintain electrical isolation
between analog input 1, digi-
tal input-outputs, switched
dc/open collector outputs and
process outputs to prevent
ground loops.
Note:
The control output common
terminal and the digital com-
mon terminal are referenced
to different voltages and
must remain isolated.
Note:
Avoid continuous writes
within loops. Excessive
writes to EEPROM will cause
premature EEPROM failure.
The EEPROM is rated for
1,000,000 writes.
Standard Bus EIA-485 Communications
Standard Bus
EIA-485
T-/R-
common
98
99
CF
CD
CE
B5
D6
D5
Slot C
T+/R+
• 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 net-
work wires in daisy-chain fash-
ion when connecting multiple
devices in a network.
• Donotconnectmorethan16
EZ-ZONE PM controllers on a
network.
• maximumnetworklength:
1,200 meters (4,000 feet)
• 1/8thunitloadonEIA-485bus
PM _ _ _ _ _-[A] AAAA _ _
Modbus RTU or Standard Bus EIA-485 Communications
Modbus RTU or
Standard Bus EIA-485
T-/R-
common
98
99
CC
CA
CB
B5
D6
D5
Slot C
T+/R+
• 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 net-
work wires in daisy-chain fash-
ion when connecting multiple
devices in a network.
• Aterminationresistormaybe
required. Place a 120 Ω resistor
across T+/R+ and T-/R- of last
controller on network.
• Onlyoneprotocolperportis
available at a time: either Mod-
bus RTU or Standard Bus.
• Donotconnectmorethan16
EZ-ZONE PM controllers on a
Standard Bus network.
• Donotconnectmorethan247
EZ-ZONE PM controllers on a
Modbus RTU network.
• maximumnetworklength:
1,200 meters (4,000 feet)
• 1/8thunitloadonEIA-485bus.
PM _ _ _ _ _-[1] AAAA _ _
Modbus-IDA
Terminal
EIA/TIA-485
Name
Watlow Termi-
nal Label
Function
DO A CA or CD T-/R-
D1 B CB or CE T+/R+
common common CC or CF common
Wiring a Serial EIA-485 Network
Two example networks are shown below where the first one is using Wat-
low's Standard Bus and the other showing connections over Modbus. Do not
route network wires with power wires. Connect network wires in daisy-chain
fashion when connecting multiple devices in a network. A termination resis-
tor may be required. Place a 120 Ω resistor across T+/R+ and T-/R- of the last
controller on a network. Only one protocol per port is available at a time: ei-
ther Modbus RTU or Standard Bus.