Modbus
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Modbus is a communication protocol, designed by Modicon for use with its programmable logic controllers (PLC)s. It is almost a de facto standard communications protocol in industry since it represents the most commonly available means of connecting almost any industrial electronic devices, which permits great savings in wiring costs. A lot of the reason for the extensive use of Modbus instead of other communications buses is the fact that it is openly published. It allows for administration of a net of devices, for instance a system that records temperature and humidity and stores results in a computer. Versions for serial port and ethernet were created. Modbus is often used to connect a supervisory computer with a remote terminal unit RTU in SCADA systems.
An extended version, Modbus Plus, remains proprietary to Modicon.
External links:
- protocol description (http://www.modicon.com/techpubs/toc7.html)
- Modbus-IDA site (http://www.modbus.org)
- Schneider Automation site (http://www.modicon.com/Default.htm)
Free software exists for modbus:
- search freshmeat (http://freshmeat.net/search/?q=modbus§ion=projects&Go.x=0&Go.y=0)
- search sourceforge (http://sourceforge.net/search/?words=modbus)