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Old January 17th, 2018, 06:58 AM   #1
AClarke678
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Can't receive any data through modbus client

Hi everyone,

I am trying to read a Modbus register in an Intelipro Unit with a S7-1200 over Modbus TCP using MB_Client. But i'm not able to receive any data through modbus client function. I am getting 16#7006 status on my modbus block stating that info is being received but the done bit is never getting activated.

I have been on with both Siemens and Comap and both companies claim I have everything set up correctly either end.

I have attached screenshots of my setup. if anyone can spot something. Any help would be greatly appreciated.
Attached Files
File Type: docx Modbus comms with Intelipro.docx (358.9 KB, 11 views)
File Type: docx Modbus DB setup.docx (218.1 KB, 6 views)
File Type: docx Modbus recieved Data.docx (230.6 KB, 4 views)
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Old January 17th, 2018, 08:11 AM   #2
BryanG
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Remote port should be 502 and Local Port can be left as zero, unless you are doing something tricky with port mapping on a router.

If that doesn't fix it you need to be doing some diagnostics on the LAN to see if data is coming out of the PLC. Disconnect the Intelipro and set you laptop to use its IP address, then run Hyperterminal or similar connected to Port 502 so that you see the data coming out of the PLC.
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Old January 17th, 2018, 11:35 AM   #3
tragically1969
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Quote:
Originally Posted by AClarke678 View Post
Hi everyone,

I am trying to read a Modbus register in an Intelipro Unit with a S7-1200 over Modbus TCP using MB_Client. But i'm not able to receive any data through modbus client function. I am getting 16#7006 status on my modbus block stating that info is being received but the done bit is never getting activated.

I have been on with both Siemens and Comap and both companies claim I have everything set up correctly either end.

I have attached screenshots of my setup. if anyone can spot something. Any help would be greatly appreciated.
Personally I would prove using ModPoll or similar from a PC that the Intellipro was indeed serving data serving data before i got anywhere near a PLC
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Old January 18th, 2018, 04:32 AM   #4
AClarke678
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I have connected the Intelipro with ModScan and can read all values within the holding registers within the Intelipro.

The port is the Intelipro is port 23 which is why i have it set to that and I have also set local port to 0 and still no data.

When I disconnect the Intelipro from the PLC (unplug the cable) the status sits at 16#7002 (Immediate Call) and moves up to 16#7006 (Information being received) when I plug the Intelipro back in, so it is seeing a connection but just doesn't display values of the registers.

I have also connected my PLC with a modbus simulator within my PC and it doesn't display any of the values I have forced through the simulator.
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Old January 18th, 2018, 08:27 AM   #5
BryanG
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Which version of MB_CLIENT are you using. I had problems with V4.0, V4.1 seemed to fix things.


Quote:
I have also connected my PLC with a modbus simulator within my PC and it doesn't display any of the values I have forced through the simulator.
Does make it look like a PLC problem, though I would be happier if you used a terminal program rather than a Modbus simulator to be certain that no data is coming out of the PLC. It just removes a layer of complication. Or if the Modbus simulator has something that just tells you what data is coming in on that port. You did reset the port on the PLC to 502 or set the simulator to use 23?

Looking at your Modbus DB Setup file I can see that you have a StatusCap variable that I am assuming is a captured Status, this is showing 16#8380 and that error is "Received Modbus frame has incorrect format or too few bytes were received."
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File Type: jpg Modbus versions.JPG (18.0 KB, 17 views)
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Old January 18th, 2018, 10:21 AM   #6
BryanG
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Also you need to think about a firewall blocking port 23, it is the normal telnet port and is very likely to be blocked on your PC.
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