LIAN 98(en) : Protocol IEC 60870-5-103, Telegram structure

IEC 60870-5-103 : Telegram structure

The LIAN 98 manual can and may not contain the complete IEC documentation, caused by legal position. Only all knowledge that is essential necessary for the LIAN 98 software operation is specified in parts in this manual.

Detailed information to the protocol you will find in the IEC-Standard-Documentation
<IEC 60870-5-103 : Telecontrol equipment and systems>
( English version EN 60870-5-103:1998 ).

Telegram format with variable length

The telegram with variable length is used for the data transmission of the user data between the controlling station and the controlled station and in the reversed direction.

Telegram format with fixed length

The telegram with fixed length is normally used for link layer services. In special cases this format with fixed length can also be used as an acknowledgement instead of a single character.

Single character

The single character is normally used in order to confirm data link services and user data.

E5H = ACK : Positive acknowledge
A2H = Not used !

Link control field :

You will find more information to the link control field in the standard documentation.
<IEC 60870-5-2 : Link transmission procedurest>
( English version EN 60870-5-2:1993 ).

RES/ DIR	Unbalanced Transmission : Reserved Balanced transmission : Physical transmission direction ( direction ) DIR = 1 : Data from controlling ( Master ) to controlled ( Slave ) station. DIR = 0 : Data from controlled ( Slave ) to controlling ( Master ) station.
PRM	Primary message : Primary bit ( primary message ) 0 = message from a secondary ( controlled ) station. 1 = message from a primary ( controlling ) station.
FCB	Primary message : frame count bit Alternating bit for consecutive SEND/ CONFIRM or REQUEST/ RESPOND messages per station. The primary station alternates the FCB bit for each new SEND/ CONFIRM or REQUEST/ RESPOND transmission service directed to the same secondary station. If an expected reply is timed out ( missing ), then the same SEND/ CONFIRM and REQUEST/ RESPOND service is repeated with the same frame count bit. In case of a reset command the FCB bit is always zero, and upon receipt of these commands the secondary station expects always that the following primary message is set with FCV = valid ( FCV = 1 ) in order to have the opposite value of FCB ( i.e. FCB = 1 ).
FCV	Primary message : frame count bit valid ) 0 = alternating function and FCB bit is invalid 1 = alternating function and FCB bit is valid SEND/ NO REPLY services, broadcast messages and other transmission services that tolerate the duplication or the deletion of information output do not alternate the FCB bit and indicate this by a cleared FCV bit.
ACD/ RES	Balanced transmission : Reserved Balanced transmission : Access demand Secondary message : Access demand There are two classes of message data provided, namely class 1 and class 2. Secondary stations indicate the primary station with it that data of class 1 are ready for transmission. 0 = no access demand on transmission of data class 1 1 = access demand on transmission of data class 1 The transmission of data class 1 is normally used for for events or for messages with high priority. Class 2 data transmission is normally used for cyclic transmission or for low priority.
DFC	Secondary message : data flow control 0 = more messages are accepted 1 = further messages can cause a data overflow Secondary ( responding ) stations indicate with this message to the initiating ( primary ) station that an immediate succession of a further message may cause a buffer overflow.

Funktion code ( FCT ) :

The function codes are described in the chapter <IEC 60870-5-103 : Simulation> later in this document.

Link address field :

Transmission procedures of the link layer are using the control field and an optional link address field.

The link address is a number for a communication interface that is used from a controlling station for the connection. It is only used as address in the communication network itself and shall not be part of the total address of a data point.

According to the standard this parameter can consist of 0, 1 or 2 octets. 0 is only valid for balanced transmission.

Type-identification ( TypeID ) :

The value ZERO is not used. The range of numbers 1 up to 127 is used for standard definitions from IEC 60870-5-101 standard. The range 128 up to 135 is reserved for routing of messages. The numbers 136 up to 255 are used for special use.

The range of numbers 128 to 255 is private and not defined in the standard, but it is recommended that the data unit identifier fields of private ASDUs have the same format as standard ASDUs.

The following table shows the definition of Type-identification numbers for process and system information in monitor and control direction.

Information in monitoring direction :

1	Time-tagged message
2	Time-tagged message with relative time
3	Measurands I
4	Time-tagged measurands with relative time
5	Identification
6	Clock synchronization
...
8	End of general interrogation
9	Measurands II
10	Generic data
11	Generic identification
...
23	List of recorded disturbances
...
26	Ready for transmission of disturbance data
27	Ready for transmission of a channel
28	Ready for transmission of tags
29	Transmission of tags
30	Transmission of disturbance values
31	End of transmission

Information in control direction :

6	Clock synchronization
7	General interrogation
...
10	Generic data
...
20	General command
21	Generic command
...
24	Order for disturbance data transmission
25	Acknowledgement for disturbance data transmission

LIAN 98 is able to process user-defined messages of non standard types up to 255, provided they have the same general telegram structure as IEC 60870-5-101 standard telegrams.

Variable structure qualifier :

The SQ bit specifies the method of addressing of the following information objects or elements.

SQ = 0
SQ = 1	Each single element or a combination of elements is addressed by the information object address. The ASDU may consist of one or more than one equal information object. The number of objects is binary coded ( number of objects ) and defines the number of the information objects.

number objects/
elements

= 0 : ASDU contains no information object
> 0 : ASDU contains one or more ( number ) information objects or elements

Cause of transmission ( COT ) :

The cause of transmission directs the ASDU to a specific application task ( program ) for processing. ASDUs in control direction are confirmed application services and may be mirrored in monitor direction with different causes of transmission. The value ZERO is not used.

...
1	spontaneous
2	cyclic
3	Reset frame count bit ( FCB )
4	Reset communication unit ( CU )
5	Start/ restart
6	Power ON
7	Test mode
8	Time synchronization
9	General interrogation
10	End of general interrogation
11	Local control
12	Distant control
...
20	Command "ACK positive"
21	Command "ACK negative"
...
31	Transmission disturbance data
...
40	Generic write command with ACK positive
41	Generic write command with ACK negative
42	Generic read command data valid
43	Generic read command data invalid
44	Generic write conformation
...

Common address of ASDU :

The "Common address" ( station address ) is equal to the link address and is valid for all objects of an ASDU.

The global address is a broadcast address directed to all stations of a specific system ( broadcast address ). ASDUs with a broadcast address in control direction have to be answered in monitoring direction by the address that is the specific defined common address ( station address ).

According to the standard this parameter can consist of 1 octets.

Function type :

The first octet in the "information object identifier" indicates the function type in the protection equipment.

128	distance protection
...
160	overcurrent protection
...
176	transformer differential protection
...
192	line differential protection
...
254	generic function type
255	global function type

Information number :

The second octet in the "information object identifier" indicates the information number within a function type. The information number is used independently in control direction and monitoring direction.

Monitoring direction :

0... 15	System functions
16... 31	State
32... 47	Supervision
48... 63	Accidental ground
64... 127	Short circuit
128... 143	Autoreclosure
144... 159	Measurands
...
240... 255	Generic Functions

Control direction :

0... 15	System functions
16... 31	General commands
...
240... 255	Generic functions

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Manual LIAN 98