Recommendations
Depending on the usage scenario, limitations or flexibilities in the Modbus TCP slave, the data mapping will vary. Therefore, the following mapping is only the prefered mapping by NODA. As such, it can be changed in agreement with NODA to match the specific situation.
Modbus mapping for a typical building
Word Order: Big Endian
Byte Order: Little Endian
| Order | Value name | Encoding | Amplification | Unit | Direction | Function Code |
|---|---|---|---|---|---|---|
| 1 | Outdoortemp | uint16 | 1/100 | Celcius | Read | 3 |
| 2 | Outdoortemp Offset | uint16 | 1/100 | Kelvin | Write | 6 |
| 3 | Primary Flow (Supply) Temperature | int16 | 1/100 | Celcius | Read | 3 |
| 4 | Primary Return Temperature | int16 | 1/100 | Celcius | Read | 3 |
| 5 | Primary Flow Volume | int16 | 1/10* | l/h* | Read | 3 |
| 6 | Primary Side Volume | int16 | 1/10* | m3* | Read | 3 |
| 7 | Primary Heat Energy | int16 | 1/10* | MWh* | Read | 3 |
| 8 | Primary Heat Power | int16 | 1/10* | kW* | Read | 3 |
| 9 | Secondary Side (#1) Flow | int16 | 1/100 | Celcius | Read | 3 |
| 10 | Secondary Side (#1) Return | int16 | 1/100 | Celcius | Read | 3 |
| 11 | Secondary Side (#2) Flow | int16 | 1/100 | Celcius | Read | 3 |
| 12 | Secondary Side (#2) Return | int16 | 1/100 | Celcius | Read | 3 |
| ... | ... | ... | ... | ... | ... | ... |
| XX | Secondary Side (#n) Flow | int16 | 1/100 | Celcius | Read | 3 |
| XX | Secondary Side (#n) Return | int16 | 1/100 | Celcius | Read | 3 |
* Depends on specific circumstances
The structure outlined in the table can repeat if the Modbus TCP slave interfaces with several regulators and or control points.
NOTE: If additional secondary side circuits exist, they should be included.
NOTE: Holding register numbers are intentionally not outlined as they likely will vary from one Modbus TCP slave to another.