Modbus ASCII Frame Tools
Generate and parse Modbus ASCII requests and responses. Calculate LRC checksums and inspect frame fields.
Modbus ASCII Request Generator
Modbus ASCII Response Generator
Data Type
Byte Order
Value(Enter a decimal value)
Modbus ASCII 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 LRC Calculator
How to Use the Frame Tools
Generate and Inspect Frames
Create Modbus ASCII requests and sample responses, check LRC, and decode captured register data. Enter complete ASCII frames when using the parser.
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.