Modbus

Modbus Configuration

This page displays the current Modbus configuration for the Cassandra system, including coils and registers organized by component groups.

Table of Contents

• Overview
• Coils
• Registers
• Function Types
• Enum and Flag Values
• References

Overview

The Modbus configuration defines all the coils and registers available in the Cassandra system. Each entry shows the address, name, component, and function type. For registers with enumerated values or flags, the possible values are displayed with their meanings.

Coils

The following table shows all configured coils grouped by their components:

Registers

The following table shows all configured registers grouped by their components:

Function Types

The tables display different Modbus function types with color-coded badges:

• 🔵 Holding Registers (FC3/FC6/FC16): Blue badges - for read/write data storage
• 🟢 Input Registers (FC4): Green badges - for read-only sensor data
• 🟠 Coils (FC1/FC5/FC15): Orange badges - for binary outputs and control
• 🟣 Discrete Inputs (FC2): Purple badges - for binary inputs and status

Enum and Flag Values

For registers with enumerated values or flags, the meanings are displayed below the register name:

• Enums: Show possible states (e.g., Status: IDLE, RUNNING, STOPPED)
• Flags: Show bit flags that can be combined (e.g., Error flags, Control flags)

Each enum or flag value shows both the numeric value and its human-readable meaning.

References

Official Documentation

• Modbus Organization - The official Modbus organization website with protocol specifications and standards
• Modbus TCP Toolkit - Official toolkit with documentation, diagnostic tools, and sample code for Modbus TCP/IP development
• Modbus Application Protocol Specification - The official protocol specification document (PDF)

Educational Articles

• Modbus Protocol Tutorial - Comprehensive tutorial covering Modbus RTU, ASCII, and TCP protocols
• Modbus Tools and Applications Guide - Detailed article by Chipkin Automation Systems about Modbus tools and applications
• Understanding Modbus Function Codes - Detailed explanation of Modbus function codes and their usage

Software Tools

Commercial Tools

• Modbus Poll - Professional Modbus master simulator for testing and debugging slave devices
• Modbus Slave - Simulator for up to 32 slave devices in separate windows
• ModScan - Diagnostic tool for testing and debugging Modbus slave devices
• ModSim - Modbus slave simulator for testing master applications

Free and Open Source Tools

• CAS Modbus Scanner - Free utility to retrieve registers from Modbus devices
• SCADACore Modbus Tools - Free tools for analyzing and debugging Modbus devices
• ModbusTools (GitHub) - Cross-platform open-source Modbus simulator with GUI support
• QModBus - Free Qt-based Modbus master application
• libmodbus - Free software library to send/receive data according to the Modbus protocol

Online Tools

• Modbus CRC Calculator - Online tool for calculating Modbus CRC checksums
• Modbus RTU Frame Calculator - Online calculator for Modbus RTU frame structure

Development Libraries

• pymodbus - Python Modbus library for client and server implementations
• node-modbus - Node.js implementation of Modbus TCP and RTU
• modbus-tk - Python toolkit for building Modbus applications
• jamod - Java implementation of the Modbus protocol