A remote-I/O station maps its first 16 commanded digital outputs as coils starting 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 coupler example uses Modbus function 01. 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 01 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 01 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 distinguish program request, output image, connection state, remote channel, field voltage and independent load feedback.
Written for controls learners proving a controller request through a remote output adapter to an interface device and observable load response.
Command owner, output tag, interlock, adapter identity, connection health, mapped data, channel type, field supply, interface load and feedback.
Program decision through output image, network connection, adapter data, output electronics, field conductor, interface device, load and return feedback.
A bounded command changes once at the controller, adapter and channel and produces the expected independently observed load state.
Connection loss, inhibited module, stale command, adapter restart, missing field power, shorted channel, wrong common, local override and controller restart.
A logic, output-image, connection, mapping, adapter, channel, supply, conductor, load or feedback mismatch.
The path commissioned with current module manuals, approved network behavior and target-machine fail-state tests.
The required fail state must be declared and verified for the exact adapter, connection and machine risk; do not assume every device clears outputs identically.
No. It indicates one channel boundary. Verify suitable electrical, actuator or process feedback when the physical result matters.