This is the home of the Free Modbus PLC Simulator

Quick-start

This free protocol simulator was originally designed to allow testing of modbus master devices over serial, hence the name: Why is it called MOD_RSSIM? Because it started out as a modbus RS232 simulator - but it grew as all applications do, and the name stuck. It also allows itself to be used as a "virtual" PLC for comms testing, training and limited use as a source-code resource. Please download it to try it out, if it works for you about 45 minutes later you will get a nag-screen, either mail me, or use my free registration-key request screen at the bottom of the page

An intuitive if not simple user-interface is my goal, next I will try guide you through how to use the simulator.

• The built-in help engine starts when you hit the universal "F1" key. You will need to have a default web-browser installed (no internet needed) to view the help.
• Setting up the simulation for use will cover it's configuration for different applications in detail. The first point we come to however is which media type the simulation should use.
• Screenshot showing Allen-Bradley MASTER protocol emulating a continuous coal miner. Selecting a different protocol opens up new options for setting up each protocol as relevant.

• Please follow the website menus to more information, like the FAQ and Help.

1. Download the simulator.
2. Run it, and select TCP/IP or serial protocol.
3. If you want serial, you can try using com0com (see the links page) to create a local loopback, and no need for a serial cable.
4. Select your serial port from the settings dialog (or if TCP/IP, simply point your HMI/SCADA to the local IP address) and connect.
5. Next you should click on the "Comms" button in the bottom-right to see the state of the communication link.

Registration Key here:  the key merely gets rid of the nag screen, click on the link to get it. It does not enable new features.

1. Download the file
2. Run it (Ignore the warning about this being unsafe)
   
3. Run the program
4. Enjoy
   

Support : If you have questions, comments or bugs to report, please fill in the form and ask your question in the comments field.

1. DOUBLE-Check your e-mail address as you type, and type your name as you like to see it. Please see the downloads page to download the simulator. If I am at home when I get the form-mail I normally respond the same evening. If not, I may be on holiday (I am also getting lots of downloads to wade through every day now),  if after a few days you get no response, check for mail quarantine, since the registration key file I will send you (a .REG file) may get munched by your mailserver, especially if it does not like my hotmail address.
   
2. Alternately mail me using this address in the graphic if I fail to respond on the form. If I detect that your mail is bouncing, I will try and sort it out without waiting for you to tell me about the problem.
   

This simulator is free, if you do like it and want to encourage it's development, please donate using the PayPal button below