Data Link

• IEC 870-5 Defines 4 different frame types

  • FT1.1, FT1.2, FT2, FT3

• IEC profiles 101, 102 and 103 specify FT1.2

• Hamming distance and residual error probability provide a measure of the reliability of the communications link

Previous slide

Next slide

Back to first slide

View graphic version

Slide 11 of 30

• Receive goes up the stack, transmit goes down the stack.
• Size of data transmitted/received may fit into one data link frame. So do not require multi-frame fragments or multi-fragment messages.
• A single DNP application function is usually sent as a single application layer message, which can consist of many data link frames.
• IEC 870-5 has no transport layer. Each data link frame containing application data is a complete application message. A single application function (e.g.: interrogation) may require that several messages are sent to complete the function.