Registers show different values depending of the range of regist

Hey !!

Thank you for your response, its an honor to be talking to the main author of the class.. ;-)

Well, i made this example using the IP address that you have provide in your test file (195.6.140.177). But the same results are given when I try with other Modbus Devices in my LAN.

The class is working well, but sometimes, there are some weird query limitations, i have other issues, like this:

In my case, I am using modbus Devices that have 588 Holding registers. I must query them in a specific order, I mean, I can't query values from 400001 to 400005, instead of that, I must query them from 400001 to 400004; or query them from 400001 to 400008.

I'm trying to figure it out if there is a Modbus limitation, a class bug or a problem with my device. I will give you all the details when I got finished jus to clarify those issues.

One more thing. I cant read Holding register "0" I mean, the memory address 400-000.

Can you please explain me what are you meaning when you say "For me the values are changing in the device between the reading queries." ??

Thank you for all your help !!!

Hi,

What is your device ? brand ? reference ? have you the specification from this device ?
When I tell about values changing...Registers in a device could change..no ? like temperature, pressure, energy meters and so on...and between two reading queries the values change...
At the origin when I wrote this class, it was planed only for Modicon PLCs from Schneider..and the register 400000 doesn't exist!
but in Jbus yes..
This means, if you read in a Modbus device the register 400001, you get the value from register 400001, if you read the register 400001 in a Jbus device you get the value from the word or register "0".

The device is an Electrical network analyzer and its extended manual can be found on this link:

"http://lit.powerware.com/ll_download.asp?file=CVM-NRG96%20power%20analyzer%20manual.pdf"

You can see all the Modbus related info between pages 31 and 34.

There is a very good example in the page 34.

There you can see the difference between your original PLC and these type of devices.