This simulator was originally created around 1999 to allow testing of a driver for a Texas Instruments 500 series controller which I had limited access to while writing the driver. A year latter I re-wrote it to support modbus RTU and TCP, basically because the simulator had allowed me not only to learn the role of master, but also of slave. So that others could benefit from the kind of test I was able to set up, I published the modbus simulator on the web in 2002. It may be used as a "virtual" PLC for training and easily simulating for test or development purposes. This simulator was written to allow the testing of a MODBUS RTU serial driver without having to get 254 little MODBUS PLCs into one office. As such it fulfills the need very well, but is not, by any means, a full implementation of the protocol; it implements only the common functions used in MODBUS and other protocols supported here.
the app, "mod_rssim.exe" you will see the splash screen similar to above for a few moments. The simulator should open the 1st available serial/RS-232 port the first time it runs, select the desired protocol (if ethernet, no serial port
is used/needed), and then click on the Port Settings..." button to change any settings.
For details on command-line usage, see section CSV Import and misc .
The first menu is the Task/System menu. Right-click on the window title.
The normal ways of controlling a window are available here, highlighted is the About box, which gives program version and contact information
Always on top - ensures that the simulator window remains on top of other windows, select it again to turn the mode off
Advanced Emulation - Takes you to the advanced emulation settings dialog relevant to the protocol you are using.
CSV Import - Import CSV files containing register values
Read only - Turns the simulator into read-only mode, registers cannot be set.
Solid Window,Alpha blend % - set the transparncy of the window, (not for windows versions < Windows2000)
Port open/close - In Serial protocols this makes the sim release the serial port so other programs can access it. The simulator is effectively disabled in this mode.
Settings are saved to WindowsTM registry.
Note: If the station indicator button for a station is off, the simulator will not respond to data requests for that station ID, even though the client is connected.
User Documentation >