1. Overview
The Omron CP1H series PLC supports both Modbus RTU master and slave functions through its built-in serial communication ports. Based on Omron's official technical documentation, this article explains the Modbus address mapping rules of the CP1H in detail.
2. Modbus Address Type Description
| Modbus Address Area | Function Code | Read/Write | Corresponding CP1H Memory Area |
|---|---|---|---|
| 0xxxx (Coils) | 01/05/15 | Read/Write | CIO area / W area / M area |
| 1xxxx (Discrete Inputs) | 02 | Read-only | CIO input area |
| 3xxxx (Input Registers) | 04 | Read-only | AR area / special area |
| 4xxxx (Holding Registers) | 03/06/16 | Read/Write | DM area / Holding area |
3. CP1H Modbus Address Mapping Table
3.1 DM Data Area → 4xxxx Holding Registers
| Modbus Address | CP1H Address | Description |
|---|---|---|
| 40001 | D0 | 0th word of the DM area |
| 40002 | D1 | 1st word of the DM area |
| 40003 | D2 | 2nd word of the DM area |
| ... | ... | And so on |
| 432768 | D32767 | Maximum address of the DM area |
Calculation formula: Modbus address = 40000 + D number + 1
3.2 CIO Area → 0xxxx Coils / 1xxxx Discrete Inputs
| Modbus Address | CP1H Address | Description |
|---|---|---|
| 00001 | CIO0.00 | Channel 0, bit 0 of the CIO area |
| 00002 | CIO0.01 | Channel 0, bit 1 of the CIO area |
| ... | ... | And so on |
3.3 W Work Area → 0xxxx Coils
The W area (work area) is also mapped to the coil area and can be read and written.
4. Modbus-RTU Simple Master Function
The CP1H Modbus master function is configured through fixed DM areas:
- Serial port 1: D32200 to D32299
- Serial port 2: D32300 to D32399
Fixed allocation area description:
| DM Address | Description |
|---|---|
| D32200 | Execution trigger (0 = not executed, 1 = execute) |
| D32201 | Slave address |
| D32202 | Function code |
| D32203-D32249 | Send data area |
| D32250-D32299 | Receive data area |
5. FAQ and Troubleshooting
- Check whether the D32200 execution trigger is fired correctly
- Confirm the slave address and function code settings
- Check the communication format (baud rate, parity)
- Make sure the fixed DM allocation area does not conflict with the program
6. Summary
Modbus address mapping rules for the Omron CP1H:
- 4xxxx Holding Registers → DM data area (D0-D32767)
- 0xxxx Coils → CIO area / W area / M area
- 1xxxx Discrete Inputs → CIO input area
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