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

The TwinCAT PLC library  TcIEC870_5_101Link.Lib implements the transmission preocedures for the transport of the ASDUs via the serial interfaces of the pc and the Beckhoff KL6xxx/EL6xxx bus terminals.

 

‘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:

 

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

Selection of application functions from IEC 60870-5-5

Application process

Application layer (7)

Selection of ASDU (service data unit of application layer) from 

IEC 60870-5-3, IEC 60870-5-4 and IEC 60870-5-101

TwinCAT PLC Library: IEC 60870-5-101 Serial Link (low level) Transport Interface

N/A

Presentation layer (6)

Session layer (5)

Transport layer (4)

Network layer (3)

  unbalanced / balanced IEC 60870-5-2
IEC 60870-5-1 (FT 1.2)

Link layer (2)

EIA RS485, RS232 (V.24), Fibre Optics

Physical layer (1)

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