Pretends to be a Modbus RTU device on a serial port, so the Modbus RTU Explorer can be exercised without hardware. It answers all eight standard function codes from an editable data set, and it can be told to misbehave in specific, reproducible ways — a device that answers slowly, or with a bad CRC, or not at all — which is the point of having it.
version · internal test instrument, not for customer use
This page has to sit on the other end of a serial link from the Explorer. Two ways to arrange that:
| Linked virtual pair (no hardware) |
Install com0com on
Windows and create a pair such as COM3 ↔ COM4. Open
COM4 here and COM3 in the Explorer. Anything written to one appears
on the other. |
|---|---|
| Two adapters | Two USB serial adapters joined by a null-modem cable, TX and RX crossed. Slower to set up, but it exercises a real UART, real baud rates and real framing errors. |
Open this page and the Explorer in separate browser windows. A serial port can only be held by one page at a time.
Everything here is off by default, so the simulator behaves like a well-mannered device until you ask it not to.
Set Highest valid holding register above zero to make everything past it answer with exception 2, Illegal Data Address — which is what a real device does when you read past the end of its map.
Seeded with values chosen so every decoder in the Explorer has something recognisable to show. Edit any cell to change what the device reports; writes arriving from the Explorer update this table live.