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MINT – IO
REF NO: m25A/om/101
Issue No: 11
Use optical isolators in RS485 line to provide protection from low
frequency interference from ground loops.
Do proper termination and/or shielding to provide isolation from high
frequency interference, RFI, and transients.
The power supply must have good filters and protection on the 220V/110V
side.
The RS485 line should have external over voltage protection to protect
from high voltage electrical noise being induced into the RS485 cable.
Make sure there is dedicated Instrumentation ground system to be used
with RS485 devices
2.4 Switch settings:
2.4.1 Setting the Modbus Node ID
Each module uses register 32010 to store the status of the DIP switches.
Switch
Function
Description
S1
Node ID +1
Node ID’s from 0 to 127 are set up using switches 1
to 7
S2
Node ID +2
“
S3
Node ID +4
“
S4
Node ID +8
“
S5
Node ID
+16
“
S6
Node ID
+32
“
S7
Node ID
+64
“
S8
BD
If ON then default comm. parameter.
S9
X1
Termination Resister 1 for RS-485 port 1
S10
X2
Termination Resister 2 for RS-485 port 2
2.4.2 RS- 485 Termination:
If DIP Switch 9 is “ON” then Termination resistance for Com port 1 is “ON”
If DIP Switch 10 is “ON” then Termination resistance for Com port 2 is “ON”
2.5 Communication Settings:
The data in the modules is stored in 16 bit registers. These registers are
accessed over the Network using the MODBUS
RTU
communication protocol.
