A coupler maps sixteen field input states as discrete inputs beginning at protocol address 0. The linked sandbox opens the exact unit, function, address, quantity and value so the reader can verify the PDU rather than copy an unexplained hex string.
Follow the workflow
This Remote-I/O digital-input module example uses Modbus function 02. Select the function from the documented object type and whether the operation is a read or write—not because two register names look similar.
Do this in the product
Open the preconfigured request and confirm the function-code label before running it.
Open the exerciseThe request transmits protocol address 0. Human-facing 0xxxx, 1xxxx, 3xxxx and 4xxxx references are notation, not values to paste blindly into the 16-bit address field.
Do this in the product
Compare the address field with the expected PDU 02 00 00 00 10.
Open the exerciseThe request quantity is 16 and the training value is 0. Multiword data, signed values, enums and decimal scales remain application-map concerns beyond the core Modbus frame.
Do this in the product
Run the server grader and read each function-specific limit check before copying the request.
Open the exerciseA normal Modbus response proves that a server accepted the request format. It does not by itself prove that a motor moved, a valve reached position or a process value is correctly scaled.
Do this in the product
Save the known-good request, then use a paid project to retain later fault and commissioning evidence.
Open the exerciseCore concepts
The simulator creates a repeatable result; these concepts make that result transferable to real vendor software and supervised practical work.
The transmitted address is a zero-based 16-bit field unless the specific device manual states a different table convention.
The expected request begins 02 00 00 00 10; TCP adds MBAP framing while RTU adds unit address, timing and CRC.
Function, address and response can be valid while units, signedness, scale or machine permissions remain wrong.
Continue in the workspace
Run the foundation exercise publicly, then use a subscription for advanced challenges, saved configurations, full attempt history, sharing, assigned paths and team reporting.
Related learning surfaces
Competency and practice field guide
Direct answer
The learner can separate field state, channel indication, adapter health, connection state, mapped data and program use, then identify the first missing transition.
Written for controls learners proving a field contact through a remote input island, industrial network connection and controller tag.
Field device, input type, supply and common, channel, adapter identity, assembly or module mapping, connection status, controller tag and data quality.
Physical contact through wiring, remote module electronics, adapter data, network transport, controller input image, alias or mapped tag and program condition.
A known open-to-closed change appears once at every declared boundary with coherent quality and timing.
Loss of field power, wrong common, duplicate address, adapter restart, stale connection, inhibited module, mismatched assembly, forcing and controller restart.
A device, conductor, channel, adapter, network, connection, mapping, tag or program-ownership mismatch.
The path commissioned with current module manuals, approved topology, cybersecurity controls and target-controller diagnostics.
Create a known safe field change and compare device, channel, adapter, network connection, controller tag and logic state in order, retaining the first boundary that fails to agree.
The input is process data; connection health indicates whether that data is current and trustworthy. Logic should not silently treat stale data as confirmed field state.