IEC 60870-5-102 : 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 60870-5-102 : Telecontrol equipment and systems>
( English version EN 60870-5-102:1996 ).

 

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 hight 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 60870-5-102 : 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 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 with time tag M_SP_TA_2
2 Accounting integrated totals, 4 octets each M_IT_TA_2
3 Accounting integrated totals, 3 octets each M_IT_TB_2
4 Accounting integrated totals, 2 octets each M_IT_TC_2
5 Periodical reset accounting integrated totals, 4 octets each M_IT_TD_2
6 Periodical reset accounting integrated totals, 3 octets each M_IT_TE_2
7 Periodical reset accounting integrated totals, 2 octets each M_IT_TF_2
8 Operational integrated totals, 4 octets each M_IT_TG_2
9 Operational integrated totals, 3 octets each M_IT_TH_2
10 Operational integrated totals, 2 octets each M_IT_TI_2
11 Periodical reset optional integrated totals, 4 octets each M_IT_TK_2
12 Periodical reset optional integrated totals, 3 octets each M_IT_TL_2
13 Periodical reset optional integrated totals, 2 octets each M_IT_TM_2

 

System information in monitor direction :

 

70 End if initialization M_EI_NA_2
71 Manufacturer and product specification of integrated total DTE P_MP_NA_2
72 Current system time of integrated total DTE M_TI_TA_2

 

System information in control direction :

 

100 Read manufacturer and product specification C_RD_NA_2
101 Read record of single point information with time tag C_SP_NA_2
102 Read record of single point information with time tag of a selected time range C_SP_NB_2
103 Read current system time of integrated total DTE C_TI_NA_2
104 Read accounting integrated totals of the oldest integration period C_CI_NA_2
105 Read accounting integrated totals of the oldest integration period and of a selected range of addresses. C_CI_NB_2
106 Read accounting integrated totals of a specific past integration period C_CI_NC_2
107 Read accounting integrated totals of a specific past integration period and of a selected range of addresses. C_CI_ND_2
108 Read periodical reset accounting integrated totals of the oldest integration period. C_CI_NE_2
109 Read periodical reset accounting integrated totals of the oldest integration period and of a selected range of addresses. C_CI_NF_2
110 Read accounting integrated totals of a specific past integration period.  C_CI_NG_2
111 Read accounting integrated totals of a specific past integration period and of a selected range of addresses.  C_CI_NH_2
112 Read operational integrated totals of the oldest integration period.  C_CI_NJ_2
113 Read operational integrated totals of the oldest integration period and of a selected range of addresses.  C_CI_NK_2
114 Read operational integrated totals of a specific past integration period.  C_CI_NL_2
115 Read operational integrated totals of a specific past integration period and of a selected range of addresses.  C_CI_NM_2
116 Read periodical reset operational integrated totals of the oldest integration period. C_CI_NN_2
117 Read periodical reset operational integrated totals of the oldest integration period and of a selected range of addresses.  C_CI_NO_2
118 Read periodical reset operational integrated totals of a specific past integration period. C_CI_NP_2
119 Read periodical reset operational integrated totals of a specific past integration period and of a selected range of addresses.  C_CI_NQ_2
120 Read accounting integrated totals of a specific past integration period of a selected time range and of a selected range of addresses.  C_CI_NR_2
121 Read periodical reset accounting integrated totals of a specific past integration period of a selected time range and of a selected range of addresses.  C_CI_NS_2
122 Read operational integrated totals of a specific past integration period of a selected time range and of a selected range of addresses.  C_CI_NT_2
123 Read periodical reset operational integrated totals of a specific past integration period of a selected time range and of a selected range of addresses.  C_CI_NU_2

 

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.

 

Further implemented ASDU's in the private range :

The TypeID numbers 128 up to 255 in the private range are for special use and are not defined in the standard. The following telegrams out of the "Spanish Red Electrica Specification" are additionaly implemented in LIAN 98.

 

128 Request of the electronic signature associated with the data ( reading integrals absolute ) M_DS_TA_2
129 Parameters of the measuring point P_ME_NA_2
130 Electronic signature associated with the measurement data ( integral part ) M_DS_TB_2
131 Date and time of change daylight savings time M_CH_TA_2
132 Loading private key signature C_PK_2
133 Read tariff information ( current values ) C_TA_VC_2
134 Read tariff information ( stored values ) C_TA_VM_2
135 Tariff information ( current values ) M_TA_VC_2
136 Tariff information ( stored values ) M_TA_VM_2
137 Close accounting period C_TA_CP_2
...    
139 Block of operational integrated totals ( absolute values ) M_IB_TG_2
140 Block of periodical reset operational integrated totals ( increment values ) M_IB_TK_2
141 Read configuration data of the meter device C_RM_NA_2
142 Configuration data of the meter device M_RM_NA_2
143 Change configuration data of the meter device C_MR_NA_2
144 Read the powers of current contract C_PC_NA_2
145 Powers of current contract expressed in watts M_PC_NA_2
146 Changing the power contract C_MC_NA_2
147 Reading holidays C_DF_NA_2
148 Sending holidays M_DF_NA_2
149 Changing holidays C_MF_NA_2
...    
180 Request of the electronic signature associated with the data ( reading integrals absolute ) C_DS_TA_2
181 Change date and time ( time synchronization ) C_CS_TA_2
182 Read parameters of the measuring point C_PI_NA_2
183 Start session and send access key ( LOGIN ) C_AC_NA_2
184 Request of the electronic signature associated with the data ( reading integrals partial ) C_DS_TB_2
185 Read date and time of change daylight savings time C_CH_TA_2
186 Request to amend the date and time of change daylight savings time C_MH_TA_2
187 Finish session ( LOGOUT ) C_FS_NA_2
188 Reserved for future versions of the protocol RM-CM C_MP_NA_2
189 Read a block of operational integrated totals of a time period and a selected address. C_CB_NT_2
190 Read a block of periodical reset operational integrated totals of a time period and a selected address. C_CB_UN_2
...    

 

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 increasing 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 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 not used  
2 not used  
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 not used  
12 not used  
13 data list not available   
14 ASDU-type not available  
15 Record address unknown  
16 ASDU address unknown   
17 Information object address unknown  
18 Measuring period not available  
...    

 

Common address of ASDU :

Octet 4 and optional 5 of the data unit identifier of the data unit define the integrated total Data Terminal Equipment. The address of the integrated total DTE is the "common address" associated with all objects of an ASDU. According to standard this parameter can consist of 1 or 2 octets. 

 

Record address :

The record address is used either as a "record address of an integration period" or a " record address of a single point information". 

 

Information object address :

The information object address is the address of an integrated total or a single point information and consists of one octet. 

In all cases the maximum number of different object addresses is limited to 255. If the information object address is not relevant ( not used ) in some ASDU's, it is set to zero.  

 

Signature :

The signature is only provided for accounting integrated totals ( TypeID 2 up to 7 ). It is the arithmetic sum modulo 256 over all octets of an integrated total and its associated identification field. This function is optional and must be parameterized analogously. 

 


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Manual LIAN 98


LIAN 98 Protocol Router, Simulator and Analyzer
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