Modbus
What this tool does
Build an RTU request for function codes 01 through 06, 15, and 16, and append the CRC. This page says what the tool is for, in plain language. The working formula stays on the signed-in tool.
When to use it
Open Modbus RTU frame builder when this is the job: Build an RTU request for function codes 01 through 06, 15, and 16, and append the CRC. That is usually a capture from the wire, a register you cannot decode, or a frame you are about to send.
Step-by-step
- Open Modbus RTU frame builder from the tool list.
- Fill Slave address, Function, Protocol address, Quantity from the instrument, the drawing, or the job record. Use the unit shown beside each field.
- Fill the remaining fields the same way. Skip a field only when the screen marks it optional.
- Run Calculate when that control is on the page, then read every result row and any warning.
- Check the result against the site procedure and the manufacturer data before you change a range, a wire, a setpoint, or a weight.
- This help page is public. Opening the tool still requires a Pro session.
Inputs
- Slave address
- 0 is broadcast. 1 through 247 are unicast. 248 through 255 are reserved.
- Function
- Choose the Function that matches the instrument, the drawing, or the job. Choices include 01 Read Coils, 02 Read Discrete Inputs, 03 Read Holding Registers, 04 Read Input Registers, 05 Write Single Coil, 06 Write Single Register.
- Protocol address
- The 0-based address in the frame. Holding reference 40001 is address 0.
- Quantity
- Reads and multiple writes. Ignored for functions 05 and 06.
- Write value
- Function 05: on or off. Function 06: one register, decimal or hex.
- Write payload hex
- Functions 15 and 16. Packed coil bytes, or register bytes in wire order.
Results
- Result
- The reported value for Modbus RTU frame builder. Use the unit printed on that row.
- Warnings
- A warning means an entry is incomplete or outside what this tool will stand behind. Recheck the inputs and the site procedure.
Common mistakes
- Pasting a frame that already includes the check bytes into a field that wants the frame without them.
- Using a holding-register reference where the frame wants the zero-based address.
- Assuming a 32-bit value is in the same word order the controller uses.
- Do not treat a result from Modbus RTU frame builder as a substitute for the site procedure or the manufacturer data.
Standards references
These are the standards and public references named on this tool. Clause numbers appear only when the catalog already cites them.
- Modbus Application Protocol Specification V1.1b (function codes 01–06, 15, and 16)
A citation that includes calculation detail stays in the signed-in workspace.
Offline and access
This engine can run offline after the server has cached it for the signed-in account.
A free session can read this help page. The tool card shows the name and the short summary. Opening the tool requires Pro.