1. Overview
The Inovance H3U series PLC is a domestic (Chinese-made) high-performance compact PLC that supports Modbus RTU master/slave functions. Based on Inovance's official technical manual, this article explains the Modbus address mapping rules of the H3U in detail.
2. Modbus Address Type Description
| Modbus Address Area | Function Code | Read/Write | Corresponding H3U Memory Area |
|---|---|---|---|
| 0xxxx (Coils) | 01/05/15 | Read/Write | Bit devices such as Y/M/S |
| 1xxxx (Discrete Inputs) | 02 | Read-only | X input relays |
| 3xxxx (Input Registers) | 04 | Read-only | AIW analog inputs |
| 4xxxx (Holding Registers) | 03/06/16 | Read/Write | D data registers |
3. H3U Modbus Address Mapping Table
3.1 X Input Relays → 1xxxx Discrete Inputs
| Modbus Address | H3U Device | Description |
|---|---|---|
| 10001 | X0 | Input relay bit 0 |
| 10002 | X1 | Input relay bit 1 |
| ... | ... | X uses octal addressing |
3.2 Y Output Relays → 0xxxx Coils
| Modbus Address | H3U Device | Description |
|---|---|---|
| 00001 | Y0 | Output relay bit 0 |
| 00002 | Y1 | Output relay bit 1 |
| ... | ... | Y uses octal addressing |
3.3 D Data Registers → 4xxxx Holding Registers
| Modbus Address | H3U Device | Description |
|---|---|---|
| 40001 | D0 | 0th data register |
| 40002 | D1 | 1st data register |
| ... | ... | And so on |
Calculation formula: Modbus address = 40000 + D number + 1
4. Master Communication Instructions
When the H3U acts as a master, it uses the MODR/MODW instructions:
- MODR: Read slave data
- MODW: Write slave data
5. FAQ and Troubleshooting
- X/Y use octal addressing; do not calculate them in decimal
- Check the communication parameter settings (baud rate, parity)
- Confirm that the slave address and register address are correct
6. Summary
The Modbus address mapping of the Inovance H3U is similar to that of the Mitsubishi FX series:
- 0xxxx Coils → Bit devices such as Y/M/S
- 1xxxx Discrete Inputs → X input relays (octal)
- 4xxxx Holding Registers → D data registers
Leave a Reply