ABB Relion 620 Series Manual page 48

Section 3
IEC 60870-5-101/104 protocol implementation
42
A special assignment of ASDUs to class 2 messages is used as follows:
Type Identification
Note: In response to a class 2 poll, a controlled station may respond with class 1 data when
there is no class 2 data available.
8.5 Application Layer
Transmission mode for application data
Mode 1 (Least significant octet first), as defined in clause 4.10 of IEC 60870-5-4, is used
exclusively in this companion standard.
Common address of ASDU
(system-specific parameter, all configurations that are used are to be marked "X")
X One octet
Information object address
(system-specific parameter, all configurations that are used are to be marked "X")
X
One octet
X
Two octets
X Three octets
Cause of transmission
(system-specific parameter, all configurations that are used are to be marked "X")
X X
One octet Two octets (with originator address). Set to zero in case of no originator address.
Cause of Transmission
X Two octets
X
Structured
X
Unstructured
1MAC302441-MB A
RER620
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