How to address tags in a Modbus device
The memory of Modicon systems is divided into four basic areas – discrete inputs, discrete outputs, input registers, holding registers. In Modicon systems, these areas are addressed absolutely (see the "Modicon addressing" column in the table below). In a Reliance project, tags are addressed relatively always starting at 0 (see the "Reliance addressing" column in the table below).
Addressing tags in a Modbus device
|
Memory area |
Modicon addressing |
Reliance addressing |
|
|
Register type |
Address |
||
|
1. Discrete outputs (Coils) |
from 00001 |
Outputs (Coils) |
from 0 |
|
2. Discrete inputs |
from 10001 |
Inputs |
from 0 |
|
3. Input registers |
from 30001 |
Input registers |
from 0 |
|
4. Holding registers |
from 40001 |
Holding registers |
from 0 |
Example
In a Reliance project, a tag at 40011 is configured this way:
Register type: Holding registers; Address: 10
For more information, go to the page with a description of Modbus Communication Driver.
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