IEC

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60870-5-104 communication protocol

Supported device types and versions
Communication partners
Communication line configuration
Communication station configuration
Tell TELL commands
I/O tag configuration
Literature
Document revisions

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Supported device types and versions

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The protocol (known also as IEC 870-5-104 or IEC-104) allows reading and writing data, operating on the basis of TCP network communication. Implementation is, according to the IEC870IEC 60870-5-104 standard, as follows:

• Originator ASDU address is 1 byte, it is defined as the line number.
• ASDU address is 2 bytes, it is defines defined as the station address. ASDU addresses of all stations on one line must be different.
• Cause of transmission is 2 bytes (contains also Originator ASDU address).
• Information object address is 3 bytes, it is defined as an I/O tag address.
• The following ASDU types are implemented in the monitoring course (from controlled station to the D2000 system and also vice-versa in balanced mode):

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Note: Single bites bits of the byte, which informs us on quality (SIQ for ASDU 1,2,30; DIQ for ASDU 3,4,31; QDS for 5..14,20,32..36) are mapped into the flags FLA A (0.bit), FLB B (1.bit) .. FLH H (7.bit) except flags except the bits that are directly set by the value of the variable ( SCO bit 0, DCO and RCS bity bits 0-1). After receiving the answer (a positive/negative one), the flags FLAA .. FLH are H flags are set according to bits of "status" byte.

For example:
for ASDU 4: FLAA=DPI bit 0, FLBB=DPI bit 1, FLCC=0, FLDD=0, FLEE=BL bit, FLFF=SB bit, FLGG=NT bit, FLHH=IV bit.
for ASDU 16: FLAA .. FLE E Sequence number bity bits 0..4, FLFF=CY bit, FLGG=CA bit, FLHH=IV bit.

Moreover:

• if a bit is set to IV (Invalid), the value state will be Invalid
• if some of the bits are set to NT (Not topical), SB (Substituted), BL (Blocked), OV (Overflow), CA (Counter adjusted), CY (Counter overflow) for corresponding ASDU types, the value state will be Weak.

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* - T-bit of the value of these ASDU types is in the FI I flag, a number within -64 .. +63 is in a variable of Ci/Ai type.

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** - ASDU 17 and 38: SEP byte is in the flags FLA  A (0.bit), FLB B (1.bit) .. FLH H (7.bit), the following 2 bytes (CP16Time2a) are in a variable of Ci/Ai type as a positive number (0-60 000) or they are in a variable of TiR type as a relative time (0-60 seconds).

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*** - ASDU 18, 39 and 40: SPE(ASDU 18,39) byte respectively OCI (ASDU 40) byte is in the flags FLI  I (0.bit), FLJ J (1.bit) .. FLP P (7.bit), QDP byte is in the the flags FLA A (0.bit), FLB B (1.bit) .. .FLH H (7.bit), the following 2 bytes (CP16Time2a) are in a variable of Ci/Ai type as a positive number (0-60 000) or they are in a variable of TiR type as a relative time.

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To set the bites bits of "status" byte (SCO for ASDU 45,58; DCO for ASDU 46,59; RCO for ASDU 47,60; QOS for ASDU 48..50,61..63), there are used the flags FLA  A (0.bit), FLB B (1.bit) .. FLH H (7.bit) are used, except the bitesbits, which are directly set by the variable value (SCO bit 0, DCO and RCS bites bits 0-1). Having received a response (positive/negative), the flags FLAA .. FLH are H flags are set according to the bites bits of the "status" byte.

When sending commands (ASDU 45-64), the value of 6 [Activation] is send sent as a CauseOfTransmission. Expecting a The expected response from the controlled station depends on the parameter the Command Confirm parameter. There are the following possibilities:
- writing is successful , if the packet with RSN confirming the SSN packet with the logwrite command
- writing is finished, if there is a response with CauseOfTransmission=7 [Activation Confirmation] and/or with 10 [Activation Termination]. Success/Unsuccess failure depends on the setting of the P/N bite in bit in CauseOfTransmission.

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**** - ASDU 250 can be used for communication with Ipesoft 870-5-104 Server. The command will ask for historical values (within any specified interval) from the server, which get back will arrive as ASDU 251 (or newer ASDU 249 that use 64-bit values for improved precision, if the protocol parameter D2H64 is enabled on the server). The reading of the archive values can be executed by means of the TELL GETOLDVAL command GETOLDVAL with the parameter containing the name of the I/O tag or station (in this case, there are read the values of all I/O tag in successive stepsare read gradually, i.e. reading another of the next tag starts after termination the reading of currently read current tag is done).
Response for ASDU 250 is again ASDU 250 (with CauseOfTransmission=7) and with the return code:

• 0 - the successful start of reading the history
• 1 - the history for the required tag doesn't existsexist
• 2 - the history for the required tag is not available (the archive does not run)

Further follows Next (is the return code was 00) the ASDU 251 with archive data will be sent and the termination ASDU 250 with CauseOfTransmission=10.

Establishing a connection:

process The D2000 KOM process is connecting to the TCP port and sends a StartDT Act U-frame StartDT Act, then a StartDT Con U-frame is waited expected as a reply.

For all the stations with a defined synchronization (see the article below), there is send an ASDU type 103 [Clock synchronisation command] with CauseOfTransmission=6 [Activation] is sent, there is expected and a reply in dependence (depending on the Command Confirm parameter) is expected.

Then there is sent a sequence of 0 up to N I-frames with ASDU 100 [Interrogation Command] and ASDU 101 [Counter Interrogation Command] is sent, both with CauseOfTransmission=6 [Activation]. The I-frames are sent for each station with at least one input I/O tag (i.e. Ai, Di, Qi, Ci). As a response, there is expected (The expected response (in any order) is:

• receiving reception of frames with ASDU 100 [Interrogation Command] and with CauseOfTransmission=7 or 10 (depends depending on the Command Confirm parameter)
• receiving reception of frames with ASDU 101 [Counter Interrogation Command] and with CauseOfTransmission=7 or 10 (depends depending on the Command Confirm parameter)
• receiving reception of current values of all I/O tags.

The other side can also sent send frames with ASDU TypeIdentificator=100 and CauseOfTransmission=10 [Activation Termination]. However, but the process D2000 KOM process does not consider it to be an error , if such no frames will not receive. are received. The order of sending ASDU 100 and 101 sending order as well as disabling their sending is defined by the parameters Order of IC and Order of Counter IC parameters.

Clock synchronisation: Sending ASDU type 103 [Clock synchronisation command] is performed during initialization (after sending StartDT and before sending Interrogation Command). The synchronization is sent for the stations, with the checked parameter Enable in the tab Enable parameter checked in the Time parameters tab. ASDU type 103 is sending sent regularly with a defined period.

Forced disconnection: If all stations on the line are in the simulation mode or the communication is stopped for them, the line will be disconnected (the communication socket will be closed). If the simulation is disabled for at least one station and the communication is not stopped for it (the the Parameters tab Parameters of Station type object), the line will be connected again (and there will be sent Interrogation Command and/or Counter Interrogation Command will be sent to the active station). After turning on every next stationenabling communication for further stations, Interrogation Command and/or Counter Interrogation Command will be sent to the stationthese stations, see the next articleparagraph.

Forced sending of Interrogation Command and/or Counter Interrogation Command: If a station is in the simulation mode, and the communication is not stopped for it (the the Parameters tab Parameters of Station type object), the process D2000 KOM process sends Interrogation Command and/or Counter Interrogation Command (see the parameters Order of IC, Order of Counter IC).

The D2000 system also supports the a balanced mode. In the this mode, the task of controlled and control stations is changed. That time, symmetrical. In this mode, the D2000 system receives commands and confirms them. The balanced mode may be used only when it is supported by the partner station. An advantage is that the D2000 system sends the current status of output I/O tags (defined as ASDU 1-40) as a reply to ASDU 100 [Interrogation Command] and 101 [Counter Interrogation Command] requests. It is still suitable to configure single-shot commands as ASDU 45 - 64; they are not repeated after re-establishing the connection.
As the protocol supports the balanced mode (partly it is a server), there are valid the rules of server protocols apply to it.
The output tags, which are configured as ASDU 1-40, do not switched to go through the Transient status (i.e. they are considered as if in the configuration of I/O tag, tab Output controlcontrol tab, the I/O tag output mode is set on to Command). The record writing is considered to be successful if there is the a connection with the server at the time of recordwriting, otherwise, the record writing is unsuccessful.

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Communication partners

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• Communication line category: TCP/IP-TCP or TCP/IP-TCP Redundant.
• TCP parameters - server parameters are mandatory:
  • Host: string containing at most 80 characters – server name in form of INET (name or numerical address a.b.c.d). In the case of redundant systems, multiple names/addresses separated by commas can be entered.
  • Port: TCP port number (0..65535)
  • Line number: is to be used as the Originator ASDU address (1 byte, 0-255)

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• Communication protocol: IEC870-TCP.
• Station address: a decimal number within the range of 0..65535 , defines the ASDU address. It can be specified as a decimal number or as a hexadecimal number with a hash at the beginning (e.g. #0A).

Note 1: After saving a station in process D2000 CNF, the process D2000 KOM automatically sends ASDU 100 and ASDU 101 (Interrogation and Counter Interrogation Commands) to this station, if enabled.

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Note 3: Starting with D2000 version 7.02.004 if a TCP Redundant line category is used, the C and D flags FLC and FLD are used in the value of communication stations for an indication of the functionality of primary (FLCC) and secondary (FLDD) communication pathpaths. If these flags are set, the respective communication path is non-functional. For example, if the value of the communication station is StON and the C flag FLC is  is set it means that only the secondary communication path is functional.
For lower versions of D2000 only partial detection of a broken communication path is available when using the parameter the Strict Redundancy Connection Signalisation.

Station protocol parameters

Table 3

 parameter.

The Browse button opens a browsing dialogue for the station address. If the communication is functional, a dialogue with the ASDU addresses received so far is displayed. The Refresh button can be used to clear the list of received ASDU addresses.

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Station protocol parameters

Table 3

Defined parameters, except for Order of IC, Order of Counter IC, and Force Slave Time, are valid for the entire line - i.e. it is enough to define them for one station on the line.

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TELL commands

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Table 4

Examples of configurations

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Example 1: Client communicating with the server SrvA

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on a redundant network.

If a communication segment drops out (e.g. IPA1 failure) the client establishes a connection with the server SrvA using the address IPA2.

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The client communicates both with the hot server and with the standby active and passive server, connection with the standby passive server continues to be open, but new values are send sent by the hot active server only.
Note: If a symbolic name myName is used in the configuration of the IEC104 Server, it should be defined as IPA in the hosts file of the 1-st server and as IPA and IPB in the hosts file of the 2-nd server as IPB.

Example 3: Client communicating with the redundant servers SrvA, SrvB

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on a redundant network.

The client communicates with both the servers. If one network segment drops out (e.g. IPA1 failure), the client establishes a connection with the SrvA server SrvA using the IPA2 address IPA2.

Example 4: The redundant clients ClientC, ClientD communicating with the redundant servers SrvA,

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SrvB on a redundant network.

The clients communicate with both the servers. If one network segment drops out (e.g. IPA1 failure), the clients establish a connection with the SrvA server SrvA using the IPA2 address IPA2. After switching the hotactive/standby passive statuses of the clients ClientC and ClientD clients, they keep communicating with the servers, but however, only the active client only sends commands. New values are sent by the active server.

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• I/O tag address is mapped on to the Information object address, i.e. it has 3 bytes and must be within the range of 0..16777215. It can be specified as a decimal number or as a hexadecimal number with a hash at the beginning (e.g. #0A).
  The I/O tag with an address starting with %IGNORE will be ignored.
  
• Input tags must be of particular types (Ai, Ci, Di, Qi) for received ASDU, see the see table 1 and also the also table 2 in the balanced mode.
• For a particular type of output tag (Ao, Dout, Co), it is necessary to set a an ASDU type, that has to be used, see the see table 2.
• Archive for providing historical values: if the client asks for historical values through ASDU 250, the server sends:
  1. the values of the historical value specified by this input entry field,
  2. if the input entry field is not filled, then the values of the historical value that archives the I/O tag,
  3. if given the specified historical value does not exist, then the values of the I/O tag that archives the control object of given the specified I/O tag,
  4. if the control object does not exist (or the archive is not available), the server returns an error.
  Specification of a historical value allows user to set configuring e.g. sending 10-minutes averages instead of sending all changes of given I/O tag.

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• Ver. 1.0 – July 30th 2003
• Ver. 1.1 – November 19th 2003: extension of supported ASDU, new parameters
• Ver. 1.2 – March 20th 2004: added ASDU for reading archive data
• Ver. 1.3 – June 20th 2004: extension - redundancy support
• Ver. 1.4 – December 1st 2004: extension - support of balanced mode
• Ver. 1.5 - December 12th, 2012 - updating, tell commands

Info
title Related pages:
Communication protocols

IEC 870-5-104 communication protocol

Supported device types and versions
Communication partners
Communication line configuration
Communication station configuration
Tell commands
I/O tag configuration
Literature
Document revisions

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The protocol allows reading and writing data, operating on the basis of TCP network communication. Implementation is, according to the IEC870-5-104 standard, as follows:

• Originator ASDU address is 1 byte, it is defined as the line number.
• ASDU address is 2 bytes, it is defines as the station address. ASDU addresses of all stations on one line must be different.
• Cause of transmission is 2 bytes (contains also Originator ASDU address).
• Information object address is 3 bytes, it is defined as an I/O tag address.
• The following ASDU types are implemented in the monitoring course (from controlled station to the D2000 system and also vice-versa in balanced mode):

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Moreover:

• if a bit is set to IV (Invalid), the value state will be Invalid
• if some of the bits are set to NT (Not topical), SB (Substituted), BL (Blocked), OV (Overflow), CA (Counter adjusted), CY (Counter overflow) for corresponding ASDU types, the value state will be Weak.

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The following ASDU types are implemented in the control course (from D2000 system to controlled station and also vice-versa in balanced mode):

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• 0 - successful start of reading the history
• 1 - the history for required tag doesn't exists
• 2 - the history for required tag is not available (the archive does not run)

Further follows (is the return code was 00) ASDU 251 with archive data and the termination ASDU 250 with CauseOfTransmission=10.

Establishing a connection:

process D2000 KOM is connecting to the TCP port and sends U-frame StartDT Act, StartDT Con is waited as a reply.

For all the stations with a defined synchronization (see the article below), there is send ASDU type 103 [Clock synchronisation command] with CauseOfTransmission=6 [Activation], there is expected a reply in dependence on the Command Confirm parameter.

Then there is sent a sequence 0 up to N I-frames with ASDU 100 [Interrogation Command] and ASDU 101 [Counter Interrogation Command], both with CauseOfTransmission=6 [Activation]. The I-frames are sent for each station with at least one I/O tag (i.e. Ai, Di, Qi, Ci). As a response, there is expected (in any order):

• receiving frames with ASDU 100 [Interrogation Command] and with CauseOfTransmission=7 or 10 (depends on Command Confirm)
• receiving frames with ASDU 101 [Counter Interrogation Command] and with CauseOfTransmission=7 or 10 (depends on Command Confirm)
• receiving current values of all I/O tags.

The other side can also sent frames with ASDU TypeIdentificator=100 and CauseOfTransmission=10 [Activation Termination], but the process D2000 KOM does not consider to be an error, if such frames will not receive. ASDU 100 and 101 sending order as well as disabling their sending is defined by the parameters Order of IC and Order of Counter IC.

Clock synchronisation: Sending ASDU type 103 [Clock synchronisation command] is performed during initialization (after sending StartDT and before sending Interrogation Command). The synchronization is sent for the stations, with the checked parameter Enable in the tab Time parameters. ASDU type 103 is sending regularly with a defined period.

Forced disconnection: If all stations on the line are in the simulation mode or the communication is stopped for them, the line will be disconnected (communication socket will be closed). If the simulation is disabled for at least one station and the communication is not stopped for it (the tab Parameters of Station type object), the line will be connected again (and there will be sent Interrogation Command or Counter Interrogation Command to the active station). After turning on every next station, Interrogation Command or Counter Interrogation Command will be sent to the station, see the next article.

Forced sending Interrogation Command or Counter Interrogation Command: If a station is in the simulation mode and the communication is not stopped for it (the tab Parameters of Station type object), the process D2000 KOM sends Interrogation Command and/or Counter Interrogation Command (see the parameters Order of IC, Order of Counter IC).

D2000 system also supports the balanced mode. In the mode, the task of controlled and control stations is changed. That time, D2000 system receives commands and confirms them. The balanced mode may be used only when is supported by partner station. An advantage is that D2000 system sends the current status of output I/O tags (defined as ASDU 1-40) as a reply to ASDU 100 [Interrogation Command] and 101 [Counter Interrogation Command] requests. It is still suitable to configure single-shot commands as ASDU 45 - 64; they are not repeated after re-establishing the connection.
As the protocol supports the balanced mode (partly it is server), there are valid the rules of server protocols.
The output tags, which are configured as ASDU 1-40, do not switched to Transient status (i.e. they are considered as if in the configuration of I/O tag, tab Output control, the I/O tag output mode is set on Command). The record is considered to be successful if there is the connection with server at the time of record, otherwise the record is unsuccessful.

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• ABB MicroScada. Note: The value of the parameter Maximum message length in the ABB MicroScada settings must be changed from 253 similar to 230 (+/- a few bytes). Default value of the parameter causes rewriting the communication buffer and it is expressed by sending a corrupted message.
• PLC Bernecker & Rainer, protocol implementation: URAP-AUTOMATIZÁCIA s.r.o. (Ltd.)
• LFC terminals of Slovenské Elektrárne, a.s. (Inc.), protocol implementation: Energodata/ABB
• RS Unicon 4, UniControls

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• Communication line category: TCP/IP-TCP or TCP/IP-TCP Redundant.
• TCP parameters - server parameters are mandatory:
  • Host: string containing at most 80 characters – server name in form of INET (name or numerical address a.b.c.d). In case of redundant systems multiple names/addresses separated by commas can be entered.
  • Port: TCP port number (0..65535)
  • Line number: is to be used as the Originator ASDU address (1 byte, 0-255)

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• Communication protocol: IEC870-TCP.
• Station address a decimal number within the range of 0..65535, defines the ASDU address.

Note 1: After saving a station in process D2000 CNF, the process D2000 KOM automatically sends ASDU 100 and ASDU 101 (Interrogation and Counter Interrogation Commands) to this station, if enabled.

Note 2: The protocol supports sending long time stamps (CP56Time2a tag) in local time or UTC time with defined offset (see the parameter Use monotonic UTC time +).

Note 3: Starting with D2000 version 7.02.004 if a TCP Redundant line category is used, the flags FLC and FLD are used in the value of communication stations for indication of functionality of primary (FLC) and secondary (FLD) communication path. If these flags are set, the respective communication path is non-functional. For example, if the value of communication station is StON and flag FLC is set it means that only secondary communication path is functional.
For lower versions of D2000 only partial detection of broken communication path is available when using the parameter Strict Redundancy Connection Signalisation.

Station protocol parameters

Table 3

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• 0 - no detection: the first connection, that detects it is working via the same network, is to be disconnected
• 1 - if ASDU contains the least significant bit of the 3rd Control Field byte set to 1
• 2 - if ASDU in CauseOfTransmission contains a bit set to 8

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• 1.bit - displays a number of incoming values during General Interrogation
• 2.bit - displays all incoming values
• 3.bit - balanced mode: requesting Interrogation command was received

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• 1.bit - balanced mode: displays a number of outgoing values during General Interrogation
• 2.bit - displays all outgoing values

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• if Ignore Control Field 3 bit 0=False (default), ASDU content is to be processed
• if Ignore Control Field 3 bit 0=True, ASDU content is to be ignored

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• if Ignore Tests=0 (default), ASDU content is to be processed
• if Ignore Tests=1, ASDU content is to be ignored
• if Ignore Tests=2, weak attribute is to be set

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• If the Destination Column is configured, then the values received from the address configured at the I/O tag and above are stored in the corresponding items (e.g. objects with addresses 10, 11, 12 ... according to the number of rows of the destination structure).

Browse

For the I/O tags, it is possible to discover the list of objects, as long as the KOM process is running and communication with a station is established.
Clicking the Browse button opens the IEC870-5-104 Item Browser window and displays a list of objects that have been read so far. The object list is created dynamically as a result of received messages.

The list of objects is dynamic, i.e. when a new value arrives in the KOM process, it is updated. Filtering in individual columns is also supported, asterisks can be used in the mask (e.g. *Short*).

Double-clicking on a particular line will cause the Address parameter to be inserted into the configuration of I/O tag from which the IEC870-5-104 Item Browser window was opened.

The Refresh button clears the list of values in both the CNF and the KOM process.

The Value column contains the received value.

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Literature

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Info
title An example of communication
The attached ZIP contains the configuration of the line, station and I/O tags for IEC104 communication. In the client subdirectory, there are line/station/I/O tag objects with the IEC 870-5-104 Client protocol, in the server subdirectory, there are line/station/I/O tag objects with the IEC 870-5-104 Server protocol, The server listens on port 2404 on the local interface (localhost). Several data and command ASDUs are configured to send the Sec and Min system tag values. View file name IEC104.zip height 150

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title Blog
You can read a blog about the IEC 870-5-104 protocol:  Communication – protocol IEC 104

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The parameter may be used to read archive values for communication with LFC terminals or other devices that support ASDU 250 defined by Ipesoft.

Unlike the primary use of ASDU 250, LFC terminal can only transmit one value for interval begin time, while the end time is ignored. The value is not to be received as ASDU 251 but as one of the standard ASDU with time stamp. What is more, the values (with the same time stamp) of other tags may be received along with the value of required tag. LFC terminal does not ASDU 250 (with CauseOfTransmission=7, 10) as part of the response and the process D2000 KOM treats the reading as done as soon as gets the value of the required IO/ tag. Reading archive values is considered as unsuccessful but connection to LFC terminal is not closed until the value is not received in the time defined by the parameter Wait Timeout T1.

If the values of other I/O tags are received along with the value of required I/O tag, they must be received before the value of required tag is received, otherwise they are not considered as archive values (because reading is consider to be done after the value of required I/O tag is done).
Example: After the request for the values of I/O tags with the addresses of 1,2..16, LFC terminal always sends the values of all the tags in the order of 1,2..16, therefore we must require for the value of the I/O tag with the address of 16.

If the parameter is not defined or LFC History=0, reading archive data are defined by Ipesoft (D2000 IEC104 Server partner is assumed).

If LFC History=1, then the value the time of which belongs into the time interval specified by the action GETOLDVAL (and transferred through ASDU 250) is considered to be historical one (it is to be stored in the archive and not I/O tag, etc.).

If LFC History=2 then see the description above for LFC History=1 except if the time of received value is later than the current value of the I/O tag, the received value is to be sent into the process D2000 Server as new one and not as historical one.

Note: When reading archive data of LFC terminal, the action GETOLDVAL may not contain station name (the parameter statIdent) but the I/O tag name. If the action contains a station name, ASDU 250 is to be sent for one I/O tag only.

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• I/O tag and station addresses
• value
• time
• flags (FA..FH)

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• number of unsuccessful connection attempts reaches the value of ST_HE or higher,
• an attempt to restore the communication lasts at least the time defined by the parameter Time filter (maximum value of all stations on line is taken into account),
• for redundant lines, the communication must be either failed for both TCP connections or there is a working TCP connection only to a standby-server (see the parameters Ignore Control Field 3 bit 0 and Ignore Tests), i.e. the data from the server are ignored.

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• if Strict Redundancy Connection Signalisation=False, the line is in order (TRUE), if at least 1 connection is working
• if Strict Redundancy Connection Signalisation=True, the line is in error state (FALSE), if both connections are working

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Defined parameters, except for Order of IC, Order of Counter IC and Force Slave Time, are valid for the entire line - i.e. it is enough to define them for one station on the line.

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Table 4

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Examples of configurations

Example 1: Client communicating with the server SrvA within redundant network.

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Server settings

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Client settings

• line: TCP (Host IPA1,IPA2, port 2404)
• protocol: IEC 870-5-104
• parameters: none

If a communication segment drops out (e.g. IPA1 failure) the client establishes connection with the server SrvA using the address IPA2.

Example 2: Client communicating with the redundant servers SrvA, SrvB.

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Servers' settings

• line: TCP/IP-TCP (Host myName or ALL, port 2404)
• protocol: IEC 870-5-104 Server
• parameters: SKO=TRUE; SWV=False; SSCF3=True;

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Client settings

• line: TCP/IP-TCP Redundant (Primary host IPA, Secondary host IPB, both ports 2404)
• protocol: IEC 870-5-104
• parameters: SKO=True;ICF3=True;

The client communicates both with the hot server and with the standby server, connection with the standby server continues to be open, but new values are send by the hot server.
Note: If symbolic myName is used, it should be defined in hosts file of 1-st server as IPA and in hosts file of 2-nd server as IPB.

Example 3: Client communicating with the redundant servers SrvA, SrvB within redundant network.

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Servers' settings

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Client settings

• line: TCP/IP-TCP Redundant (Primary host IPA1,IPA2, Secondary host IPB1,IPB2, both ports 2404)
• protocol: IEC 870-5-104
• parameters: ICF3=True

The client communicates with both the servers. If one network segment drops out (e.g. IPA1 failure), the client establishes connection with the server SrvA using the address IPA2.

Example 4: The redundant clients ClientC, ClientD communicating with the redundant servers SrvA, SrvBwithin redundant network.

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Servers' settings

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Clients' settings

• line: TCP/IP-TCP Redundant (Primary host IPA1,IPA2, Secondary host IPB1,IPB2, both ports 2404)
• protocol: IEC870-5-104
• parameters: SKO=True; SWV=False;ICF3=True

The clients communicate with both the servers. If one network segment drops out (e.g. IPA1 failure), the clients establish connection with the server SrvA using the address IPA2. After switching the hot/standby statuses of the clients ClientC and ClientD, they keep communicating with the servers, but the active client only sends commands. New values are sent by the active server.

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Possible I/O tag types: Ai, Ao, Ci, Co, Di, Dout, Qi

• I/O tag address is mapped on Information object address, i.e. it has 3 bytes and must within the range of 0..16777215.
• Input tags must be particular types (Ai, Ci, Di, Qi) for received ASDU, see the table 1 and also the table 2 in the balanced mode.
• For particular type of output tag (Ao, Dout, Co) it is necessary to set a ASDU type, that has to be used, see the table 2.
• Archive for providing historical values: if client asks for historical values through ASDU 250, the server sends:
  1. the values of the historical value specified by this input entry field,
  2. if the input entry field is not filled, then the values of the historical value that archives the I/O tag,
  3. if given historical value does not exist, then the values of the I/O tag that archives the control object of given I/O tag,
  4. if the control object does not exist (or the archive is not available), the server returns an error.
  Specification of a historical value allows user to set e.g. sending 10-minutes averages instead of sending all changes of given I/O tag.

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Kotva
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Document revisions

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• Ver. 1.0 – July 30th, 2003
• Ver. 1.1 – November 19th, 2003: extension of supported ASDU, new parameters
• Ver. 1.2 – March 20th, 2004: added ASDU for reading archive data
• Ver. 1.3 – June 20th, 2004: extension - redundancy support
• Ver. 1.4 – December 1st, 2004: extension - support of balanced mode
• Ver. 1.5 - December 12th, 2012 - updating, tell commandsTELL commands
• Ver. 1.2 – November 16th, 2023 (support for the Destination Column)
  
  

Info
title Related pages:
Communication protocols

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