Overview
This document defines the Modbus register map for communication between the Dilution Control System and PLC. Register addresses shown are configurable in the PLC Configuration dialog.
Address Convention
Addresses shown are 0-based register addresses. Some PLC software uses 1-based addressing. Add 1 if your system expects 1-based addresses.
Setpoint Registers
Valve position setpoints written by the control system to the PLC:
Float Format (Recommended)
| Register | Count | Type | Description | Range |
|---|---|---|---|---|
0 |
2 | FLOAT32 | Zone 1 Setpoint | 0.0 - 100.0 % |
2 |
2 | FLOAT32 | Zone 2 Setpoint | 0.0 - 100.0 % |
4 |
2 | FLOAT32 | Zone 3 Setpoint | 0.0 - 100.0 % |
| ... continues for all zones (2 registers per zone) | ||||
2×(N-1) |
2 | FLOAT32 | Zone N Setpoint | 0.0 - 100.0 % |
Integer Format (Alternative)
| Register | Count | Type | Description | Range |
|---|---|---|---|---|
0 |
1 | UINT16 | Zone 1 Setpoint | 0 - 32767 |
1 |
1 | UINT16 | Zone 2 Setpoint | 0 - 32767 |
| Scale: 32767 = 100% | ||||
Feedback Registers
Valve position feedbacks read from the PLC by the control system:
Float Format
| Register | Count | Type | Description | Range |
|---|---|---|---|---|
1000 |
2 | FLOAT32 | Zone 1 Feedback | 0.0 - 100.0 % |
1002 |
2 | FLOAT32 | Zone 2 Feedback | 0.0 - 100.0 % |
| ... continues for all zones (2 registers per zone) | ||||
Status Registers
Zone and system status information:
| Register | Count | Type | Description |
|---|---|---|---|
2000 |
1 | UINT16 | Zone 1 Status (see Status Codes) |
2001 |
1 | UINT16 | Zone 2 Status |
| ... continues for all zones | |||
2100 |
1 | UINT16 | Global Mode (0=Auto, 1=Manual) |
2101 |
1 | UINT16 | System Status |
2102 |
1 | UINT16 | Heartbeat Counter |
Control Registers
Control commands from PLC to Dilution Control System:
| Register | Count | Type | Description | Values |
|---|---|---|---|---|
3000 |
1 | UINT16 | Control Enable | 0=Disable, 1=Enable |
3001 |
1 | UINT16 | Flush Command | 1=Start Flush |
3002 |
1 | UINT16 | Reset Command | 1=Reset to Defaults |
Example 48-Zone Configuration
Register Layout Summary
| Setpoints (FLOAT32) | 0 - 95 |
96 registers (48 × 2) |
| Feedbacks (FLOAT32) | 1000 - 1095 |
96 registers (48 × 2) |
| Zone Status (UINT16) | 2000 - 2047 |
48 registers |
| System Registers | 2100 - 2110 |
Global status |
| Control Registers | 3000 - 3010 |
Commands |
Configuration Flexibility
All base addresses are configurable. Use the PLC Configuration dialog to set addresses that match your PLC program structure.