Modbus RTU Frame Tools
Generate requests and responses, parse Modbus RTU frames, and calculate CRC-16 checksums.
Modbus RTU Request Generator
Modbus RTU Response Generator
Data Type
Byte Order
Value(Enter a decimal value)
Modbus RTU Frame Parser
Parsing Rules
Byte Offset
Data Type
Original Bytes
Byte Order
Reordered Bytes
Parsed Frame
Actions
Add a rule to decode values from the payload.
Modbus CRC-16 Calculator
How to Use the Frame Tools
Serial and RTU troubleshooting
Read article: Modbus RTU Guide: Frames, CRC and Register Values · CRC-16 check · Register addresses and offsets
Generate and Inspect Frames
Create Modbus RTU requests and sample responses, check CRC-16, and decode captured register data. Choose a data type and byte order that match your device.
What you can do:
- Generate requests for the eight common read and write function codes.
- Build sample response frames for tests and comparison.
- Decode payload values using byte offsets, numeric types and byte orders.
Build a Request
- Device address: use 1–247 for a serial device. Address 0 is broadcast and receives no reply; 248–255 are reserved.
- Function code: choose 01/02/03/04/05/06/15/16 in decimal; 15 and 16 are 0x0F and 0x10.
- Start address: the zero-based protocol offset, not a reference number such as 40001.
- Quantity: number of bits or 16-bit registers to read or write.
- RTU request examples:
- 01 03 00 00 00 02 C4 0B — read two holding registers starting at address 0.
- 01 06 00 00 00 01 48 0A — write 1 to holding register address 0.
Build a Sample Response
- Choose the same function code as the request.
- Add register values using signed, unsigned or IEEE 754 types.
- Choose ABCD, DCBA, BADC or CDAB to match the device.
- RTU response examples:
- 01 03 04 00 01 00 02 2A 32 — two registers containing 1 and 2.
- 01 06 00 00 00 01 48 0A — a successful single-register write echoes the request.
Decode a Captured Frame
- Paste a complete frame from the selected Modbus format.
- Add a rule for each value you want to read from the payload.
- Choose the signed, unsigned or IEEE 754 type from the register map. Hex Converter
- Select the byte order used by the device.
- For saved RTU read responses, open the serial debugger and choose File as the parsing source.