Help with modbus addressing-Solved

[viktor_au]

Thanks Steve

I think the main problem with studying the Modbus protocol is that the different industries use the different titles.

I found the next line on www:

Documentation for Modbus is not well standardized. Actually there is a standard, but not well followed when it comes to documentation.

From now on I have to use FC8 modbus Master as it is without thinking too much about 40001, 40002, etc, as those numbers (correct me) are important only for some industrial setups.
I will try to use in my Weather station the Master setup with 1st Modbus Map Address as N0 (40001) and will use it as a default (mapping scheme?) to communicate with all 5 or 6 station Nodes.

I still have some interest to find out the difference between Master register name, register number and register type.
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Found some answers

Register types: Coil, Discrete Input, Input Register, Holding Register.
Register range: 00001-09999 with adding at frong: 0,1,2,3 to change the type.
know the difference between holding register 40001 and coil 40001. If coil 40001 is the target, it must appear as 040001.

More answers, what explain a good move of Matrix team to re-calculate/hide the 40001 scheme to use/show the Zero indexed scheme


Difference in modbus mapping/scheme


There are generally three standards for this mapping, but even that gets messed up by manufacturers.
Here are the three:
1. Zero indexed mapping.
2. 40001 mapping - original scheme.
3. 400001 (extended) mapping

AzeoTech, 2016: "40001 mapping. This is the original mapping scheme of Modbus created way back when. In this case, the digit in the 10,000's place indicates what type of register you want. no digit (0) = coil, 1 = input status, 3 = input register, and 4 = holding register. The funny part is that those numbers don't line up with the corresponding function code. For example, to read an input register you usually use function code 4, and to read a holding register you use 3. Go figure! Other than indicating the function to use, the 10,000's place has no meaning to the actual address so gets stripped off. "

Read more:
https://support.azeotech.com/topic/5909 ... ess-limit/

[Steve001]

there is a standard - I will put something together later for you

modbus was developed in 1979 by modicon for there PLC's and is widely utilised

have a look at Modbus.org

Steve