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Author Topic: Modbus TCP Addressing from IFM Controller  (Read 6711 times)


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Modbus TCP Addressing from IFM Controller
« on: February 11, 2008, 01:10:22 PM »
I am using a H2-ECOM100 to communication with an IFM Controller of an AS-i network.  The controller seems to be working and the ECOM seems to be functioning properly, however I cannot get the data to read accross the peer-to-peer network. 

  - Using NetEdit I setup the ECOM peer-to-peer Node 2 with the IP address from the IFM Controller.
  - The IFM is set to Gateway function with the Modbus selection enabled
  - The D2-250 PLC instruction is as follows:
LD K302 (Slot 3, Node 2)
LD K16 (8 Words)
LDA O2000 (Write to V2000 Memory Location)
RX V10000 (Read from Modbus Address 4096)

I am confused about the exact address to read from the IFM.  My instruction book shows the data addresses starting at 4096 Hex.


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Re: Modbus TCP Addressing from IFM Controller
« Reply #1 on: February 12, 2008, 09:36:07 AM »
You wrote "the data addresses starting at 4096 Hex"... If this is so, then 4096 hex = 40226 octal, and since V-memory is octal I don't believe the RX V10000 is correct. The RX V10000 would cause the H2-ECOM100 to send out a Modbus TCP telegram utilizing FC03 (Read Holding Registers) at offset +4097. Some Modbus TCP controllers call this address +44097, or some just call it Holding Register 4097.

(1)  Is your peer-to-peer configuration set to use Modbus TCP?
(2)  What FC does the IFM require to read the "data addresses"?
(3)  Are the "data addresses" considered to be Holding Registers? Or Input Registers?
(4)  Do the "data addresses" really start at 4096 "Hex"? Or 4096 decimal?
« Last Edit: February 12, 2008, 09:37:45 AM by Greg »
There are two types of people in the world; those that can extrapolate from incomplete data sets.