IEC 60870-5-101 : 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 60870-5-101 : Telecontrol equipment and systems>
( English version EN 60870-5-101:2003 ).

 

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 procedures>
( 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

Unbalanced 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 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.

 

Functions code ( FCT ) :

The function codes are described in the chapter <IEC 60870-5-101 : Simulation> later in this document.

 

Link address fields :

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.

 

Process information in monitoring direction :

 

1 Single point information M_SP_NA_1
2 Single point information with time tag M_SP_TA_1
3 Double point information M_DP_NA_1
4 Double point information with time tag M_DP_TA_1
5 Step position information M_ST_NA_1
6 Step position information with time tag M_ST_TA_1
7 Bit string of 32 bit M_BO_NA_1
8 Bit string of 32 bit with time tag M_BO_TA_1
9 Measured value, normalized value M_ME_NA_1
10 Measured value, normalized value with time tag M_ME_TA_1
11 Measured value, scaled value M_ME_NB_1
12 Measured value, scaled value with time tag M_ME_TB_1
13 Measured value, short floating point value M_ME_NC_1
14 Measured value, short floating point value with time tag M_ME_TC_1
15 Integrated totals M_IT_NA_1
16 Integrated totals with time tag M_IT_TA_1
17 Event or protection equipment with time tag M_EP_TA_1
18 Packed start events of protection equipment with time tag M_EP_TB_1
19 Packed output circuit information of protection equipment with time tag M_EP_TC_1
20 Packed single point information with status change detection M_PS_NA_1
21 Measured value, normalized value without quality descriptor M_ME_ND_1

 

Process telegrams with long time tags ( 7 octets ) :

 

30 Single point information with time tag CP56Time2a M_SP_TB_1
31 Double point information with time tag CP56Time2a M_DP_TB_1
32 Step position information with time tag CP56Time2a M_ST_TB_1
33 Bit string of 32 bit with time tag CP56Time2a M_BO_TB_1
34 Measured value, normalized value with time tag CP56Time2a M_ME_TD_1
35 Measured value, scaled value with time tag CP56Time2a M_ME_TE_1
36 Measured value, short floating point value with time tag CP56Time2a M_ME_TF_1
37 Integrated totals with time tag CP56Time2a M_IT_TB_1
38 Event or protection equipment with time tag CP56Time2a M_EP_TD_1
39 Packed start events of protection equipment with time tag CP56time2a M_EP_TE_1
40 Packed output circuit information of protection equipment with time tag CP56Time2a M_EP_TF_1

 

Process information in control direction :

 

45 Single command C_SC_NA_1
46 Double command C_DC_NA_1
47 Regulating step command C_RC_NA_1
48 Set point command, normalized value C_SE_NA_1
49 Set point command, scaled value C_SE_NB_1
50 Set point command, short floating point value C_SE_NC_1
51 Bitstring 32 bit C_BO_NA_1

 

Command telegrams with long time tag ( 7 octets ) :

 

58 ( IEC 104 ) Single command with time tag CP56Time2a C_SC_TA_1
59 ( IEC 104 ) Double command with time tag CP56Time2a C_DC_TA_1
60 ( IEC 104 ) Regulating step command with time tag CP56Time2a C_RC_TA_1
61 ( IEC 104 ) Set point command, normalized value with time tag CP56Time2a C_SE_TA_1
62 ( IEC 104 ) Set point command, scaled value with time tag CP56Time2a C_SE_TB_1
63 ( IEC 104 ) Set point command, short floating point value with time tag CP56Time2a C_SE_TC_1
64 ( IEC 104 ) Bitstring 32 bit with time tag CP56Time2a C_BO_TA_1

 

System informationen in monitoring direction :

 

70 End if initialization M_EI_NA_1

 

System information in control direction :

 

100 (General-) interrogation command C_IC_NA_1
101 Counter interrogation command C_CI_NA_1
102 Read command C_RD_NA_1
103 Clock synchronization command C_CS_NA_1
104 Test command C_TS_NB_1
105 Reset process command C_RP_NC_1
106 Delay acquisition command C_CD_NA_1
107 ( IEC 104 ) Test command with time tag CP56Time2a C_TS_TA_1

 

Parameter in control direction :

 

110 Parameter of  measured value, normalized value P_ME_NA_1
111 Parameter of  measured value, scaled value P_ME_NB_1
112 Parameter of  measured value, short floating point value  P_ME_NC_1
113 Parameter activation P_AC_NA_1

 

File transfer :

 

120 File ready F_FR_NA_1
121 Section ready F_SR_NA_1
122 Call directory, select file, call file, call section F_SC_NA_1
123 Last section, last segment F_LS_NA_1
124 Ack file, ack section F_AF_NA_1
125 Segment F_SG_NA_1
126 Directory F_DR_TA_1
127 ( IEC 104 ) QueryLog Request archive file F_SC_NB_1

 

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

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.

SQ = 1

A sequence of equal information objects ( e.g. measured values of identical format ) is addressed by the information object address. The information object address specifies the associated address of the first information element of the sequence. The following information elements are identified by numbers continuously by + 1 from this offset. The number of objects is binary coded ( number of elements ) and defines the number of the information elements. In case of a sequence of information elements only one information object per ASDU is allocated.

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.

 

P/ N

The P / N-bit indicates the positive or negative confirmation of an activation requested by a primary application function. In the case of irrelevance the P/N-bit is zero.

T

In addition to the cause the test-bit defines ASDUs which were generated during test conditions. The test bit is used e.g. to test transmission and equipment without controlling the process.

 

...    
1 periodic, cyclic  
2 background interrogation  
3 spontaneous  
4 initialized init
5 interrogation or interrogated req
6 activation act
7 confirmation activation actcon
8 deactivation deact
9 confirmation deactivation deactcon
10 termination activation actterm
11 feedback, caused by distant command  
12 feedback, caused by local command  
13 data transmission  
...    
20 interrogated by general interrogation inrogen
21 interrogated by interrogation group 1  
22 interrogated by interrogation group 2  
23 interrogated by interrogation group 3  
24 interrogated by interrogation group 4  
25 interrogated by interrogation group 5  
26 interrogated by interrogation group 6  
27 interrogated by interrogation group 7  
28 interrogated by interrogation group 8  
29 interrogated by interrogation group 9  
30 interrogated by interrogation group 10  
31 interrogated by interrogation group 11  
32 interrogated by interrogation group 12  
33 interrogated by interrogation group 13  
34 interrogated by interrogation group 14  
35 interrogated by interrogation group 15  
36 interrogated by interrogation group 16  
37 interrogated by counter general interrogation  
38 interrogated by interrogation counter group 1  
39 interrogated by interrogation counter group 2  
40 interrogated by interrogation counter group 3  
41 interrogated by interrogation counter group 4  
...    
44 type-Identification unknown  
45 cause unknown  
46 ASDU address unknown  
47 information object address unknown  
...    

 

Originator address :

The originator address directs mirrored ASDUs and interrogated ASDUs in monitor direction (e.g. interrogated by a general interrogation) to the source that activated the procedure ( in case of redundant systems ).

If the originator address is not used and there is more than one single source in a system defined, the ASDUs in monitor direction have to be directed to all relevant sources of the system. In this case the specific affected source has to select its specific ASDUs..

 

Common adddress of ASDU :

The common address is associated with all objects in 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 monitor direction by the address that is the specific defined common address ( station address ). According to the standard this parameter can consist of 1 or 2 octets.

 

Information object address :

The information object address is used as destination address in control direction and as source address in monitor direction.

The third octet is only used in case of structuring the information object address in order to define unambiguous addresses within a specific system. In all cases the maximum number of different object addresses is limited to 65 535 ( as for two octets ). If the information object address is not relevant ( not used ) in some ASDUs, it is set to zero.

 


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Manual LIAN 98


LIAN 98 Protocol Router, Simulator and Analyzer
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