Modbus RTU Online Tools
Professional Modbus RTU online tool suite providing command generation, message parsing, online debugging, and CRC verification functions. Installation-free, supports browser direct serial connection, the essential tool for industrial automation development and debugging.
šÆ Modbus RTU One-Stop Solution
Integrated professional Modbus RTU tool suite combining command generation, message parsing, online debugging, and CRC verification. Supports all standard function codes, multiple data types and byte orders, making your Modbus development and debugging more efficient.
ā Why Choose Our Modbus RTU Tools?
šÆ Main Application Scenarios
Industrial Automation Debugging
Debug PLCs, frequency converters, instruments and other Modbus devices
- Device Communication Testing
- Parameter Reading Configuration
- Fault Diagnosis Troubleshooting
Device Integration Development
Develop Modbus master or slave programs
- Protocol Verification Testing
- Data Format Confirmation
- Compatibility Testing
System Maintenance Operations
Production line equipment maintenance and data collection
- Regular Data Collection
- Device Status Monitoring
- Historical Data Analysis
š Get Started Now
No registration required, no download needed, open your browser to use the complete Modbus RTU tool suite. Supports direct serial connection, making your device debugging simpler and more efficient.
š Modbus RTU Protocol Knowledge
Modbus RTU (Remote Terminal Unit) is a serial transmission mode of the Modbus protocol, using binary encoding and CRC verification, characterized by high transmission efficiency and strong error detection capability. It is widely used for communication between devices in industrial automation systems.
Key Features:
- Binary data format, high transmission efficiency
- CRC16 verification, strong data reliability
- Supports RS485 multi-point communication
- High standardization, good compatibility
A standard Modbus RTU frame consists of the following parts:
[Slave Address][Function Code][Data Area][CRC Checksum]- Slave Address: 1 byte, identifies the target deviceļ¼
- Function Code: 1 byte, specifies the operation typeļ¼
- Data Area: N bytes, contains address and dataļ¼
- CRC Checksum: 2 bytes, ensures data integrityļ¼
- 01: Read Coil Status
- 02: Read Discrete Inputs
- 03: Read Holding Registers
- 04: Read Input Registers
- 05: Write Single Coil
- 06: Write Single Register
- 15: Write Multiple Coils
- 16: Write Multiple Registers
Modbus RTU uses the CRC-16 verification algorithm with polynomial 0xA001. The verification process ensures data transmission reliability and is an important component of the Modbus RTU protocol.
Verification Features:
- 16-bit cyclic redundancy check
- Polynomial: 0xA001
- Initial value: 0xFFFF
- Low byte first transmission
In Modbus projects, data types (integers/floats) and byte orders (ABCD/DCBA/BADC/CDAB) directly affect how register values are parsed and displayed. The points below help you read/write correctly:
- Signed integers use two's complement: MSB is the sign bit; negatives = bitwise NOT + 1. When parsing HEXāINT, sign-extend to the target bit width
- Floats follow IEEEā754: FLOAT32 = 1 sign + 8 exponent + 23 fraction (bias 127); FLOAT64 = 1 sign + 11 exponent + 52 fraction (bias 1023). Supports Ā±0, Ā±ā, NaN and subnormals
- Four common byte orders: ABCD (bigāendian) / DCBA (littleāendian) / BADC (16ābit word swap) / CDAB (32ābit group swap). For 16ābit data, usually only ABCD/DCBA matter
- Byte endianness vs word order: endianness describes byte order; word order describes the order of 16ābit registers. For 32/64ābit data both often apply
- 64ābit integers and JS safe integers: browser Number is IEEEā754 double; safe integers are Ā±(2^53ā1). Tool uses BigInt for 64ābit; outāofārange or precision risk shows '-'
- Normalize HEX input: strip nonāHEX, uppercase, pad leading 0 to even length, and display grouped every 2 chars for readability
- Decimal with fraction: if input has a decimal point and target is an integer type, show '-'. Only FLOAT32/FLOAT64 accept fractions
- Debug tip: if unsure about byte order, try all four patterns with a known value and compare; always follow device documentation