IEC 60870-5-101:1995/AMD2:2001

Amendment 2 - Telecontrol equipment and systems - Part 5-101: Transmission protocols - Companion standard for basic telecontrol tasks

General Information

• Status: Published
• Publication Date: 24-Oct-2001
• ICS: 33.200 - Telecontrol. Telemetering
• Technical Committee: TC 57 - Power systems management and associated information exchange
• Drafting Committee: WG 3 - TC 57/WG 3
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 07-Feb-2003

Relations

• Amends: IEC 60870-5-101:1995 - Telecontrol equipment and systems - Part 5: Transmission protocols - Section 101: Companion standard for basic telecontrol tasks
• Effective Date: 05-Sep-2023
• Revised: IEC 60870-5-101:2003 - Telecontrol equipment and systems - Part 5-101: Transmission protocols - Companion standard for basic telecontrol tasks
• Effective Date: 05-Sep-2023

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
60870-5-101
AMENDMENT 2
2001-10
Amendment 2
Telecontrol equipment and systems –
Part 5-101:
Transmission protocols –
Companion standard for basic telecontrol tasks

 IEC 2001  Copyright - all rights reserved
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International Electrotechnical Commission
For price, see current catalogue

– 2 – 60870-5-101 Amend. 2 © IEC:2001(E)

FOREWORD
This amendment has been prepared by IEC technical committee 57: Power system control and

associated communications.
The text of this amendment is based on the following documents:

FDIS Report on voting
57/535/FDIS 57/551/RVD
Full information on the voting for the approval of this amendment can be found in the report on

voting indicated in the above table.
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until 2003. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
_____________
Page 7
1 Scope and object
Add, after the third paragraph, the following new text:
Although this companion standard defines the most important user functions, other than the
actual communication functions, it cannot guarantee complete compatibility and interoperability
between equipment of different vendors. An additional mutual agreement is normally required
between concerned parties regarding the methods of use of the defined communication
functions, taking into account the operation of the entire telecontrol equipment.
2 Normative references
Insert, in the list, the titles of the following standards:
IEC 60870-5-103:1997, Telecontrol equipment and systems – Part 5-103: Transmission
protocols – Companion standard for the informative interface of protection equipment
ISO/IEC 8824-1:2000, Information technology – Abstract Syntax Notation One (ASN.1):
Specification of basic notation

Page 17
5 Physical layer
5.1 Selections from ISO and ITU-T standards
Add, on page 19, after 5.1.3, the following new subclause:
5.1.4 Other compatible interfaces
Physical interfaces other than those which are recommended in the IEC 60870-5 series may be
used, according to agreement between user and vendor. However, if other interfaces are used,
it is the responsibility of the user and the vendor to prove their functionality and interoperability.

60870-5-101 Amend. 2 © IEC:2001(E) – 3 –

Page 21
6 Link layer
6.1 Selections from IEC 60870-5-1: Transmission frame formats

Add, after the notes, the following new text:

Transmission rule R3 states that no idle line intervals are admitted between characters. This
may not be possible to achieve in some practical implementations, particularly with high bit rate
transmission, because of unavoidable hardware or software delays.
However, annex B demonstrates that a line idle interval between characters that has a duration
not longer than one transmitted bit time does not reduce the frame integrity. Therefore,
transmission rule R3 may be relaxed to allow line idle intervals of up to one transmitted bit time
duration between characters. The line idle intervals between characters extend the
transmission time of time critical information (for example, clock synchronization) which may
reduce the accuracy of clocks in controlled stations.
There is no requirement for the receiver to measure line idle intervals between characters. For
example, the receiver may be implemented using an industry standard UART circuit alone,
without any special hardware or software concerned with the duration of gaps between
characters in a received frame.
6.2 Selections from IEC 60870-5-2: Link transmission procedures
Add, after the third paragraph, the following new subclause:
6.2.1 State transition diagrams
This subclause adds more detail to the base definitions of link transmission procedures given
in IEC 60870-5-2. State transition diagrams are used to define the procedures more exactly so
that link layers implemented by different manufacturers can be made fully interoperable. State
transition diagrams represent the states (in this case of the link layer defined in IEC 60870-5-2)
and the transitions from one state into another. The actions (send Tx and receive Rx) are
included. In addition to the states, important internal processes are described.
The state transition diagrams are presented in the format defined by Grady Booch/Harel. The
explanation of the particular elements is shown in figure 75.

State 1 State 2
Event[condition]/action B
in: action A
IEC  1612/01
Figure 75 – State transition diagram by Grady Booch/Harel
The word "in" describes an action which is triggered when a transition into a new state occurs.
The transition to the next state may be triggered by the termination of the current state, in the
case where there is no defined event to cause the transition.

– 4 – 60870-5-101 Amend. 2 © IEC:2001(E)

The notation used in the following state transition diagrams is:

FC0 to FC15 = function code number 0 to 15, see tables 1 to 4 of IEC 60870-5-2

FCB = frame count bit
FCV = frame count bit valid
DFC = data flow control
ACD = access demand
PRM = primary message
SC = single character
Replace the heading "UNBALANCED TRANSMISSION" by:
6.2.1.1 Unbalanced transmission procedures
Add, after the fourth paragraph of 6.2.1.1, the following new text:
The SEND/NO REPLY service is used when issuing a user data message to all stations
(broadcast address).
Add, after the second sentence of the sixth paragraph, the following new text:
The assignment of the causes of transmission to the two classes is defined in 7.4.2.
Add, after the sixth paragraph, the following new text:
Table 10 shows the permissible combinations of the unbalanced link layer procedures.
Table 10 – Permissible combinations of unbalanced link layer services
Function codes and services Permitted function codes and services
in the primary direction in the secondary direction
<0> Reset of remote link <0> CONFIRM: ACK or
<1> CONFIRM: NACK
<1> Reset of user process <0> CONFIRM: ACK or
<1> CONFIRM: NACK
<3> SEND/CONF user data <0> CONFIRM: ACK or
<1> CONFIRM: NACK
<4> SEND/NO REPLY user data No reply

<8> REQUEST for access demand <11> RESPOND: status of link
<9> REQUEST/RESP request status of link <11> RESPOND: status of link
<10> REQUEST/RESP request user data class 1 <8> RESPOND: user data or
<9> RESPOND: requested data not available
<11> REQUEST/RESP request user data class 2 <8> RESPOND: user data or
<9> RESPOND: requested data not available
Responses <14> Link service not functioning or <15> Link service not implemented are also
permitted. The single control character E5 may be used instead of a fixed length CONFIRM
ACK (secondary function code <0>) or fixed length RESPOND NACK (secondary function code
<9>) except when there is an access demand for class 1 data (ACD = 1) or further messages
may cause an overflow (DFC = 1). This is shown in figures 77 and 78. The single character A2
must not be used.
60870-5-101 Amend. 2 © IEC:2001(E) – 5 –

For unbalanced transmission procedures: The primary station contains only a primary link layer

and the secondary station contains only a secondary link layer (see figure 76). More than one

secondary station may be connected to one primary station. Compatible communication

between the primary station and a particular secondary station relies on these two stations

alone. The polling procedure for requesting data from multiple secondary stations is a local

internal function of the primary station and need not be shown in figures 76 to 78.
Consequently, these diagrams only show the primary station and a single secondary station. In
the case of more than one secondary station, the primary station has to remember the current

state of each secondary station.

STATION A
Link layer is primary only
Link layer
primary
PRM = 0 PRM = 1
Receiver Transmitter
Transmitter Receiver
PRM = 1
PRM = 0
Link layer
secondary
STATION B
Link layer is secondary only
IEC  1613/01
Figure 76 – Unbalanced transmission procedures, primary and secondary stations
Figure 77 shows the state transition diagram of the primary station, figure 78 that of the
secondary station.
– 6 – 60870-5-101 Amend. 2 © IEC:2001(E)

NOTE 1 The primary link layer NOTE 4 The service FC1 (sent from
refers to a particular station primary) is not presented,

A, the secondary link layer since the use has to be
Reset of the
refers to the partner station
defined according to the
B in this figure. primary link
specific application.
layer
NOTE 2 IND means an indication to
NOTE 5 T0 is the time out
the service user.
for repetition of
frames, Trp is the
NOTE 3 The single character may

repetition timer or
be used instead of a FC0
retry mechanism.
or FC9 except ACD=1 or
[]/
DFC=1.
A
Waiting for a REQ
from the service
user
REQ[]/start Trp
Execute
request status of link
in: Tx: FC9
Rx[error]/ and Trp not time out T0 time out[]/CON(error status)
(request status of link)
or: Rx[FC14 or FC15]/ or: Trp time out[]/CON(error status)
or: Rx[FC11,DFC=1]/
Rx[FC11,DFC=0]/
Execute
reset secondary link
A
T0 time out[]/CON(error status)
in: Tx: FC0
or: Trp time out[]/CON(error status)
Rx[error]/and Trp not time out
(reset of remote link)
or: Rx[FC1(NACK)]/
or: Rx[FC14 or FC15]/
Rx[FC0(Ack)]/IND("station responds again")
Link layer primary
REQ[send data with no reply]/
and secondary
Tx: FC4(send/no reply)
available
REQ[send/confirm]/start of timer Trp
REQ[request class 1 or class 2
or status of link]/start of timer Trp

Execute service Execute service
request/respond send/confirm
Rx[FC8]/CON(data)
Rx[FC0]/
or: Rx[FC9]/
or: Rx[FC1]/ IND("data not
in: Tx: FC9 or in: Tx: FC3
or: Rx[FC11]/
accepted") *
FC10 or FC11
or: Rx[FC14 or FC15]/
or: Rx[FC14 or FC15]/ IND("data
CON("error status")
not accepted") *
* Number of repetitions is
defined by the service user
A
T0 time out[Trp time out]/ IND("station does
not respond")
A
or: Rx[error, Trp time out]/ IND("station not
T0 time out[Trp time out]/ IND("station
responding correctly")
T0 time out[Trp not time out]/
does not respond")
T0 time out[Trp not time out]/
or: Rx[error]/ Trp not time out/
or: Rx[error, Trp time out]/IND("station
or: Rx[error]/ Trp not time out/
not responding correctly")
IEC  1614/01
Figure 77 – State transition diagram for unbalanced transmission primary to secondary

60870-5-101 Amend. 2 © IEC:2001(E) – 7 –

NOTE 1 The secondary link layer
NOTE 2 IND means an indication to
refers to a particular station
the service user.
Link layer secondary
B, the primary link layer
NOTE 3 The single character may
not reset
refers to the partner station
be used instead of a FC0
A in this figure.
or FC9 except ACD=1 or
DFC=1.
Rx[FC0 to 15 except 9
and 0]/no reply
Rx[FC9]/Tx FC11
Rx[FC0]/Tx FC0
Execute reset of
secondary link layer
in: FCB=0
Monitor line idle
between frames
[]/
A
Sufficient time idle
Link layer Rx[FC0]/Tx FC0
available
Rx[error]/
Rx[FC9]/Tx:FC11
or: Rx[FC not implemented]/Tx:FC15
Rx[FC4]/
IND(data)
Evaluate
Rx[FC3]/
request/respond
[further messages
[FCB not changed]/
are acceptable] Rx[FC10 or FC11]/
Tx(last message)
[changed FCB]/IND("request")
Waiting on RESP
Evaluate
of the service user
send/no reply
Evaluate
send/confirm
A
RESP[data]/Tx:FC8
[further messages
or: RESP[no data]/Tx:FC9
cause overflow]
A
[FCB not changed]/Tx FC0
[FCB changed, further messages [FCB changed, further messages are
cause overflow]/ TxFC0,DFC=1, acceptable]/ Tx:FC0, IND(Data)
IND(data)
Secondary link layer
A
busy
[further messages are acceptable again]/
Rx[error]
Rx[FC0]/Tx FC1, DFC=1
Monitor line idle
or: Rx[FC3]/Tx FC1, DFC=1
between frames
or: Rx[FC4]/IND("error")
or: Rx[FC10 or FC11, user data]/Tx FC8, DFC=1 *)
[sufficient time idle]
or: Rx[FC10 or FC11, requested data not available]/
Tx FC9, DFC=1 *
or: Rx[FC not implemented]/Tx FC15, DFC=1
* as evaluate request/respond after "link layer
available"
IEC  1615/01
Figure 78 – State transition diagram for unbalanced transmission secondary to primary

– 8 – 60870-5-101 Amend. 2 © IEC:2001(E)

Replace the heading "BALANCED TRANSMISSION" by:

6.2.1.2 Balanced transmission procedures

Add, after the first paragraph of 6.2.1.2, the following:

The following table shows the permissible combinations of the balanced link layer procedures

Table 11 – Permissible combinations of balanced link layer services

Function codes and services Permitted function codes and services

in the primary direction in the secondary direction
<0> Reset of remote link <0> CONFIRM: ACK or
<1> CONFIRM: NACK
<1> Reset of user process <0> CONFIRM: ACK or
<1> CONFIRM: NACK
<2>SEND/CONF test function for link <0> CONFIRM: ACK or
<1> CONFIRM: NACK
<3> SEND/CONF user data <0> CONFIRM: ACK or
<1> CONFIRM: NACK
<4> SEND/NO REPLY user data No reply
<9> REQUEST/RESP request status of link <11> RESPOND: status of link
Responses <14> link service not functioning or <15> link service not implemented are also
permitted. The single control character E5 may be used instead of a fixed length CONFIRM ACK
(secondary function code <0>) except when further messages may cause an overflow (DFC = 1).
Add, after the second paragraph, the following new text:
The link layers for balanced transmission procedures consist of two decoupled logical
processes, one logical process represents station A as the primary station and station B as the
secondary station and the other logical process represents station B as the primary station and
station A as the secondary station (each station is a combined station). Thus, two independent
processes exist in each station to control the link layer in the logical primary and in the
secondary direction. Figure 79 shows the typical arrangement of the link layer using balanced
transmission procedures.
NOTE The physical transmission direction is fixed defined by the bit DIR. The logical processes primary or
secondary may change from station A to B and vice versa. The primary message is defined by the bit PRM = 1, the

secondary message by the bit PRM = 0 (see 6.1.2 of IEC 60870-5-2).

60870-5-101 Amend. 2 © IEC:2001(E) – 9 –

STATION A
Link layer Link layer
secondary
primary
...