A training pump controller accepts a run command at coil protocol address 10 after local permissives are satisfied. 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 Pump controller example uses Modbus function 05. 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 10. 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 05 00 0A FF 00.
Open the exerciseThe request quantity is 1 and the training value is 1. 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 05 00 0A FF 00; 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 network write, application request, PLC permission, final output and physical or simulated pump feedback and diagnose the first mismatch.
Written for pLC and industrial-communications learners issuing a bounded simulated pump request through a documented coil point.
Authorized client, server and point identity, write function, coil offset, requested state, command ownership, mode, process permissives, pump availability, final output, run feedback and timeout.
Network write through server coil and PLC request handling to permissives, motor command, pump rotation, flow or pressure response and returned status.
One authorized run request starts the permitted simulated pump and stop removes the command with coherent run and process feedback.
Wrong mode, no permissive, competing owner, invalid coil, pump trip, no run feedback, no flow, timeout, duplicate request, communication loss and restart.
An authority, identity, point, network, owner, mode, permissive, output, pump, feedback or process mismatch.
The real command path reviewed and tested under approved process, electrical, network and operating procedures.
Not necessarily. The written point should normally become a request that still passes through mode, permissive, interlock, output and equipment-feedback logic.
Read back the request and controller status, then confirm motor run and the required process response such as flow or pressure independently.