LIAN 98(en) : Protocol IEC 60870-5-101, Telegram structure

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 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 :

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