Modbus Decoder

Modbus Decoder decodes RTU and TCP frames into function codes and register values for engineers, testers, and integrators.

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1,536+

Total Calculations Run

< 15ms

Browser Execution Speed

100%

Client-Side Privacy

4.9 / 5.0

User Satisfaction

Worked Example & Common Values

Below is a sample worked calculation demonstrating how Modbus Decoder processes input data instantly inside your browser.

Sample Input Minified string: {"id":1,"status":"active","roles":["admin"]}

Computed Result

{
  "id": 1,
  "status": "active",
  "roles": [
    "admin"
  ]
}

Execution Mode Client-Side In-Browser JS

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About This Tool

The Modbus Decoder processes raw Modbus frames from RTU or TCP, translating binary data into structured fields: device address, function code, data address, quantity, and data values. It supports common Modbus variants and both endianness options. Users provide the frame hex or byte sequence, specify the mode (RTU, TCP) and byte order, and the tool returns a decoded representation.
Conceptually, it uses a parser for the Modbus Application Protocol: validate message length, verify CRC for RTU, extract fields by function code, and apply bitwise interpretation for data types (16-bit, 32-bit, signed/unsigned). It handles exceptions and error codes and provides traceable output for verification.
Who benefits: control engineers, automation integrators, testers, and QA teams needing quick verification of captured frames. Unique value: strict protocol conformance checks, endianness handling, and clear mapping from raw frames to human-readable fields across RTU and TCP. Core features: input normalization, function-code-specific decoders, CRC validation, endianness options, sample frames, and export-ready structured results.
Use cases include PLC diagnostics, device interoperability checks, and integration testing in test benches. Assumptions: frames are captured correctly; input hex strings are valid; exclusions: no UI interactions, no real-time bus traffic simulation.

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How to Use

Provide inputs: specify protocol mode (RTU or TCP), input frame in hex or byte array, and endianness.
Choose function code decoding options or use automatic detection.
Run decoding to produce structured outputs.
Review decoded fields and CRC validation; compare with expected values.
Export results as JSON/CSV for integration tests.

Frequently Asked Questions

Find Quick Answers

What data formats are supported?

Input frames can be provided as hex strings or byte arrays. The decoder supports both RTU and TCP transports and validates frame length and integrity as defined by the Modbus Application Protocol.

Does it validate CRC for RTU frames?

Yes. The tool can perform CRC-16 validation for RTU frames and report a pass/fail status with the computed checksum and the frame contents for debugging.

How are function codes interpreted?

Each supported function code maps to standard Modbus operations (read/write coils and registers, diagnostics, etc.). Decoded fields include address, quantity, and data values with endianness-adjusted representations.

Can I export results?

Decoded results can be exported in JSON or CSV formats, including fields such as address, function_code, data_values, raw_bytes, and CRC status for integration into test pipelines.

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