Author Topic: Modbus map?  (Read 6026 times)


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Modbus map?
« on: November 09, 2013, 10:21:50 AM »
Can anyone explain how a relay status can be assigned to modbus address?


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Re:Modbus map?
« Reply #1 on: July 30, 2014, 04:37:46 AM »
Not sure I understand your question? The PLC comes with the data sheet that shows you the Modbus address table and reference of each PLC IO.

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Re:Modbus map?
« Reply #2 on: August 26, 2015, 06:45:58 PM »

I'm assuming here that you want to connect over the LAN and not RS485.

Firstly you need to connect to the plc you want to write to/read from. The following command will do that:


The IP address is the one for the destination plc. The 502 at the end is necessary as it is the port number that is used by MODBUS over tcp/ip

Next, write to a location on the destination plc use the following command:

WRITEMODBUS 4,1,1101,DM[50]

In this instance I am writing to an DM location on the destination PLC from a DM location on the source PLC. How do I know the destination is a DM location? It is the 1000 at the beginning of the 1101 (check chapter 14, pg 10 of the manual). I am actually writing to DM[100] on the destination PLC, you can read the manual to see how the numbers work out.
The 4 at the beginning is the port I'm going out on the source, 4 because I'm using the ethernet socket. The following 1 is the Id of the destination plc, seems redundant but necessary
The DM[50] is the location of the data on the source plc.

Hopefully this makes some sort of sense. It will be very similar for RS485.



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