M-system SC100 - 4.7. Modbus-RTU SC200;210; 4.7.1. Modbus-RTU CONNECTION

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SC100/200 Series Users Manual EM-6337-B Rev.15
4.7. Modbus-RTU
SC200/210
The Modbus protocol is provided by Modicon Inc. (AEG Schneider Automation International S.A.S.), originally developed
for Modicon programmable controllers. Detailed information is described in Modicon Modbus Protocol Reference Guide
(PIMBUS-300 Rev. J).
The Modbus master can monitor and control the SC200/210 using command (query) and response transactions.
For more information about Modubs protocol, please refer to Modbus Protocol Reference Guide (EM-5650).
4.7.1. Modbus-RTU CONNECTION
Use independently shielded twisted pair cables (CPEV-S φ0.9) to connect between Modbus-RTU devices. DO NOT use
bound cables, in order to eliminate unexpected interference from other signal lines.
An entire segment must be inside one building, with the maximum cable length of 500 m.
Cross Wiring
• Cross wire between each device referring to the illus-
tration to the right.
• Be sure to connect (+) to (+) and (–) to (–).
• Connect shield terminal as designated for each de-
vice. For devices with no shield terminal, connect be-
tween the shields of each device.
• Earth the shield at single, independent ground point
within the system (grounding resistance 100 Ω or
less). The most appropriate point depends upon sys-
tems. There are also cases when leaving the shield
ungrounded gives a better result.
Terminating Resistor
• Connect a terminating resistor at both ends of the seg-
ment.
• Terminating resistor is incorporated in each device.
Close across T2 and T3 terminals to activate it. Con-
sult each device’s specications for exact terminal as-
signment of the resistor.
+
–
+
–
Jumper
T4
T1
T2
T3
To Other
Modbus-RTU
Devices
To Other
Modbus-RTU
Devices
Cross Wiring
+
–
T4
T1
T2
T3
To Other
Modbus-RTU
Devices
Termination Resistor
■ Modbus-RTU
R2K-1
ControllerController
CONNECTOR
RS-232-C
RS-485
*1
*1
*1. Internal terminating resistor is used when the device is at the end of a transmission line.
*2. Install shield cables to all sections and ground them at single point.
*2
FG
RS-485
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4