Modbus

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.

External links:

• protocol description
• Modbus-IDA site
• Schneider Automation site

Free software exists for modbus:

• search freshmeat
• search sourceforge