Quantum w/NOE and addressing question

R

Thread Starter

Rob

Hi,

I have a 3rd party Modbus TCP device connected to a Quantum System through a NOE module. When I try to read the holding registers down at the lower addresses around 40001, everything works fine and the data is passed between the device and the Quantum and shows up in the Quantum memory map. The 3rd party device has some registers that are at the 41000, 42000 and 43000 areas of the holding registers and when I try to read these addresses, the Quantum system doesn't show the transferred data. Looking at the packet captures, I can see the Quantum request and the devices response containing the correct data, but yet the data never moves into the Quantum memory map. There are no communication errors shown by the Quantum so it believes everything is OK and yet no data. Any ideas of what's going on? Is there some limitation that the Quantum has for the addressing scheme? I'm at a loss to explain this.

Thanks, Rob
 
If your Quantum reports no errors, then we can assume that either it is not configured correctly (no offense, and no...I'm not a Quantum guru but I know Modbus alright) - or the 3rd party device responds in a way that is not proper error response. Modbus has a lot built in that several (in my experience) 3rd party vendors often don't 'bother' to implement. For example, I've dealt with devices that simply ignore (rather than replying with the proper error code) messages with screwed up checksums.

that's my .02
 
B

Bruce Durdle

How many holding registers have you configured into the Quantum PLC? - Check the Configuration screen.

Bruce
 
B
I have not heard of this issue. Have you checked to see if the data that is expected in 401000 is not in fact goint to 410000. Perhaps there is a "misundertanding" with the target's understanding of 5 vs 6 digit addressing. 400001 and 40001 would be OK, but higher address references may not be.
 
When I use a packet sniffer, I can see the response along with the correct data being sent back to the Quantum, so it's not an addressing or error problem.
 
There was a new firmware release in January for the Quantum and that fixed the problem. Per Modicon, "Don't even think of using the older firmware."
 
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