How To Connect The Rs-422/485 Interface - Mitsubishi Electric QJ71MB91 User Manual

Modbus interface module
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6
PRE-OPERATIONAL PROCEDURES AND SETTINGS

6.5.2 How to connect the RS-422/485 interface

This section describes connection precautions and a connection example for using the
QJ71MB91 RS-422/485 interface.
(1) Connection precautions
(a) When connecting SG and FG signal lines
(b) Connecting cable's shield
SDA
SG
SDB
FG
RDA
FG
RDB
Correspondence between RS-422/485 terminal block and signal position
When connecting the QJ71MB91 side SG and FG signal lines to the target
device, connect them according to the specifications of the target device.
Connect the shield of the connection cable to either FG terminal on the connected
device.
If normal data communication is not available due to external noise even with the
above-mentioned wiring, perform the following wiring.
1) Make connection between the FGs of both stations with the shield of the
connection cable.
For the target device side, follow the instruction manual of the target device.
2) Connect the (FG) of the QJ71MB91 to the FG terminal of the power supply
module on the station to which the QJ71MB91 is installed, or to the FG
terminal of the control panel on which the QJ71MB91 programmable controller
is installed.
3) Connect nnA and nnB of each signal line of the connection cable in a pair.
QJ71MB91 side
SDA
SDB
RDA
RDB
SG
(FG)*1
(FG)*1
Figure 6.11 RS-422/485 cable shield
* 1 The QJ71MB91's FG terminal can be connected to either one.
6.5.2 How to connect the RS-422/485 interface
Shield
6.5 Connection to a Target Device
1
2
3
4
5
Target device side
RDA
RDB
SDA
SDB
SG
FG
6
7
8
6
- 14

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