TcIEC870_5_101Link: IEC 60870-5-101 Serial Link Interface (master/slave)

‘Low level’ interface: IEC 60870-5-101 Serial Link Interface

This interface starts lower down on the protocol stack and enables the sending and/or receipt of individual frames (ASDUs).

Pro: Very flexible; all properties in the ASDU frame can be changed (e.g. an own time stamp, Select/Execute or a special command execution etc.); high performance can be achieved because only the necessary services are implemented; high performance if there are many data points;

Contra: Larger amount of programming work; all services, such as general query, counter query, time synchronisation, command execution, spontaneous data transmission etc. must be implemented by the PLC programmer himself (programmed out); the PLC programmer must be familiar with the protocol standard.

This interface is recommended if you:

• are familiar with the protocol standard;
• are implementing a protocol converter application;
• are implementing virtually all available standard functions in the application;
• are using special functions, such as the relaying of the time stamp from a Modbus device or the gaining of control over the command execution;
• require functions that are not supported according to the compatibility list;
• have many data points (>1000) and need high performance;

This interface is placed inside the protocol structure above the link layer (2) and implements necessary transport functions and frame formats. Application functions like for example the general interrogation, time synchronisation or counter interrogation are not implemented in the interface, but the user can implement them by himself.

Protocol structure of endsystem:

Requirements

Remark: The layers 3..6 are not used.