5
ModBus
5.1 Introduction
Many protocols have been designed for the needs of industrial automation and metering. These protocols generally use simple query/response models and allow for extremely simple implementations. Many protocols derived from the frame formats defined by IEC 870-5 such as:
- T101 (IEC 870-5-101) that was generated by the IEC TC57 for electric utility communication between master stations and remote terminal units, it is also based on the IEC-870-5-x link layer, using frame format FT 1.2.
- DNP 3.0, a protocol originally designed by Westronic, Inc. that was released into the public domain in 1993, based on the IEC-870-5-x link layer with a few modifications (e.g., use of FT3 frames for asynchronous, rather than synchronous, communication, inclusion of both source and destination addresses).
- M-Bus (see Section 9.3)
- Profibus, a fieldbus initially designed by Siemens and later standardized as IEC 61 158 (“Digital Data Communication for Measurement and control, Fieldbus for use in industrial control systems” for versions DP-V0, DP-V1 and DP-V2) and IEC 61 784 (Communication Profile Family DPF3). The protocols user's association website is http://www.profibus.com/.
Other protocols developed independently into de-facto standards, such as ModBus, a very common protocol that is used in many industrial and HVAC installations.
5.2 ModBus Standardization
ModBus is a trademark of Modicon inc (Schneider Electric group), which also maintains the standard. The ModBus standard ...
