Five documents specify the base IEC 60870-5. The documents are:
- IEC 60870-5-1 Transmission Frame Formats
- IEC 60870-5-2 Data Link Transmission Services
- IEC 60870-5-3 General Structure of Application Data
- IEC 60870-5-4 Definition and coding of Information Elements
- IEC 60870-5-5 Basic Application Functions
The IEC Technical Committee 57 also generated a companion standard IEC 60870-5-101 especially for remote controlled units RTU, connected to a Controlling Station either via V24(RS232) or RS485 serial communication. The IEC 60870-5-101 is based on the five documents IEC 60870-5-1 to 5.
Interoperability between devices by different vendors is ensured by the interoperability list, which is defined by the standard. In the list, the function range is defined for each device by marking the applicable functions. The common denominator between different vendor lists limits the possible function range.
As the original standard left more room for interpretation, there were many different implementations on a wide range of different devices many of which are mutually incompatible. To remedy this situation, major energy utilities, such as RWE, Bayernwerke (E.ON), have developed their own
IEC 60870-5-101 based standards. The "Norwegian IEC 870-5-101 User Convention", managing line redundancy in particular, has found wide acceptance in Scandinavian countries.
IEC 60870-5-101
is known for the resilience of its link layer and for its simply structured application layer. The main focus was placed on on performance definition, so that some information needed for data decoding is not transmitted. For data decoding to work, parameter settings such as information object length, ASDU address length etc. need to be correct. This is not much of a problem, as interoperability lists help to achieve this.
