Modbus Protocol
Table of Contents
- Overview
- Quick Link
- Key Features
- Supported Functions
- Communication Methods
- Data Types
- Error Codes
Overview
Modbus is a widely used communication protocol in industrial automation. It operates on a master-slave architecture and supports data exchange between various industrial equipment.
Quick link
Related Protocols: SECS/GEM | EtherNet/IP | OPC UA | RTSP
Key Features
- Simplicity: Simple and easy-to-understand protocol structure
- Openness: Open standard supported by various vendors
- Reliability: Error detection and recovery capabilities
- Scalability: Usable in various network environments
Supported Functions
| Function |
Description |
| Read Coils |
Read digital output status |
| Read Discrete Inputs |
Read digital input status |
| Read Holding Registers |
Read holding registers |
| Read Input Registers |
Read input registers |
| Write Single Coil |
Write single coil |
| Write Single Register |
Write single register |
| Write Multiple Coils |
Write multiple coils |
| Write Multiple Registers |
Write multiple registers |
Communication Methods
| Method |
Description |
Characteristics |
| Modbus RTU |
Serial communication |
Binary encoding, high efficiency |
| Modbus ASCII |
Serial communication |
ASCII encoding, easy debugging |
| Modbus TCP |
Ethernet communication |
TCP/IP based, high-speed communication |
Data Types
| Type |
Description |
Range |
| Coil |
1-bit read/write |
0 or 1 |
| Discrete Input |
1-bit read-only |
0 or 1 |
| Holding Register |
16-bit read/write |
0-65535 |
| Input Register |
16-bit read-only |
0-65535 |
Error Codes
| Code |
Description |
| 01 |
Illegal Function |
| 02 |
Illegal Data Address |
| 03 |
Illegal Data Value |
| 04 |
Slave Device Failure |
| 05 |
Acknowledge |
| 06 |
Slave Device Busy |
| 08 |
Memory Parity Error |
| 0A |
Gateway Path Unavailable |
| 0B |
Gateway Target Device Failed to Respond |