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

Supported device types and versions

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):

Table 1

ASDU type I/O tag type
1 - Single-point information Di, Qi (On/Off), Ai, Ci
2 - Single-point information with time tag Di, Qi (On/Off), Ai, Ci
3 - Double-point information Qi, Ai, Ci
4 - Double-point information with time tag Qi, Ai, Ci
5 - Step position information Ci, Ai *
6 - Step position information with time tag Ci, Ai *
7 - Bitstring of 32 bits Ci, Ai
8 - Bitstring of 32 bits with time tag Ci, Ai
9 - Measured value, normalized value Ai
10 - Measured value, normalized value with time tag Ai
11 - Measured value, scaled value Ci, Ai
12 - Measured value, scaled value with time tag Ci, Ai
13 - Measured value, short floating point value Ai
14 - Measured value, short floating point value with time tag Ai
15 - Integrated totals Ci, Ai
16 - Integrated totals with time tag Ci, Ai
17 - Event of protection equipment with time tag Ci, Ai, TiR **
18 - Packed start events of protection equipment with time tag Ci, Ai, TiR ***
20 - Packed single-point information with status change detection Ci, Ai
21 - Measured value, normalized value without quality descriptor Ai
30 - Single-point information with time tag CP56Time2a Di, Qi (On/Off), Ai, Ci
31 - Double-point information with CP56Time2a tag Qi, Ai, Ci
32 - Step position information with CP56Time2a tag Ci, Ai *
33 - Bitstring of 32 bits with CP56Time2a tag Ci, Ai
34 - Measured value, normalized value with CP56Time2a tag Ai
35 - Measured value, scaled value with CP56Time2a tag Ci, Ai
36 - Measured value, short floating point value with time tag CP56Time2a Ai
37 - Integrated totals with time tag CP56Time2a Ci, Ai
38 - Event of protection equipment with time tag CP56Time2a Ci, Ai, TiR **
39 - Packed start events of protection equipment with time tag CP56Time2a Ci, Ai, TiR ***
40 - Packed output circuit information of protection equipment with time tag CP56Time2a Ci, Ai, TiR ***
241 - 64-bit floating point value (Ipesoft & URAP implementation) Ao
243 - 64-bit floating point value with time tag CP56Time2a (Ipesoft & URAP implementation) Ao
251 - Archive data values (Ipesoft's implementation) none ****
252 - D2000 Unival (Ipesoft's implementation) all (except Qi)

Note: Single bites 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 (0.bit), FLB (1.bit) ..FLH (7.bit) except the bits that are directly set by the value of variable ( SCO bit 0, DCO and RCS bity 0-1). After receiving the answer (a positive /negative one), the flags FLA..FLH are set according to bits of "status" byte.

For example:
for ASDU 4: FLA=DPI bit 0, FLB=DPI bit 1, FLC=0, FLD=0, FLE=BL bit, FLF=SB bit, FLG=NT bit, FLH=IV bit.
for ASDU 16: FLA..FLE Sequence number bity 0..4, FLF=CY bit, FLG=CA bit, FLH=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.

* - T-bit of the value of these ASDU types is in the FI flag, a number within -64 .. +63 is in a variable of Ci/Ai type.
** - ASDU 17 and 38: SEP byte is in the flags FLA (0.bit),FLB (1.bit)..FLH (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).

*** - ASDU 18, 39 and 40: SPE(ASDU 18,39) byte respectively OCI (ASDU 40) byte is in the flags FLI (0.bit),FLJ (1.bit) ..FLP (7.bit), QDP byte is in the flags FLA (0.bit),FLB (1.bit)...FLH (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.

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

Table 2

ASDU type I/O tag type
45 - Single command Dout
46 - Double command Dout
47 - Regulating step command Dout
48 - Set point command, normalised value Ao
49 - Set point command, scaled value Co
50 - Set point command, short floating point value Ao
51 - Bitstring of 32 bit Co
58 - Single command with time tag CP56Time2a Dout
59 - Double command with time tag CP56Time2a Dout, Co
60 - Regulating step command with time tag CP56Time2a Dout
61 - Set point command, normalised value with time tag CP56Time2a Ao
62 - Set point command, scaled value with time tag CP56Time2a Co
63 - Set point command, short floating point value with time tag CP56Time2a Ao
64 - Bitstring of 32 bit with time tag CP56Time2a Co
250 - Archive data request command (Ipesoft's implementation) none ****
252 - D2000 Unival (Ipesoft's implementation) all

To set the bites 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 (0.bit),FLB (1.bit) ..FLH (7.bit) except the bites, which are directly set by the variable value ( SCO bit 0, DCO and RCS bites 0-1). Having received a response (positive/negative), the flags FLA..FLH are set according to the bites of the "status" byte.

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

**** - ASDU 250 can be used for communication with Ipesoft 870-5-104 Server. The command will ask for historical values (within any interval) from the server, which get back 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 command GETOLDVAL with the parameter containing the name of the I/O tag or station (in this case, there are read values of all I/O tag in successive steps, i.e. reading another tag starts after termination of currently read tag).
Response for ASDU 250 is again ASDU 250 (with CauseOfTransmission=7) and with the return code:

  • 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.

Communication partners

  • 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

Communication line configuration

  • 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)

Communication station configuration

  • 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

Full name Meaning Unit Default value
Asymetric Redundancy Mode Periodicity The parameter can be used for a TCP Redundant line with defined backup servers (see the parameters AS1, AP1, BS1, BP1 ..). Non-zero value of ARMP parameter means that if this number of ASDUs is received (after a successful reconnect), both connection are checked whether they're not going through the same network (IP a ports defined in the line settings or ASx:APx and BSx:BPx).If they do, the connection to the standby server (see the parameter Asymetric Redundancy Mode Slave Detection) will be closed and an attempt to establish a connection through another network will be made. If unsuccessful, the following IP address will be tried (i.e. Alternate Server 1, Alternate Server 2, line IP, Alternate Server 1 etc).
Note: When the parameter Asymetric Redundancy Mode Periodicity is enabled, the second connection is established to "B-Alternate Server 1" : "B-Alternate Port 1" and not to the IP address and port defined for the line after running the process D2000 KOM (so that it wouldn't be immediately closed). 		- 0
Asymetric Redundancy Mode Slave Detection Detection method of standby server for Asymetric Redundancy Mode Periodicity:
  • 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
 - 0
Alternate Server 1/
Alternate Port 1/
Alternate Server 2/
Alternate Port 2/		 Extension for redundant systems: beside the IP address defined in the configuration of the Line, it is possible to define 2 alternative IP addresses. In case of connection failure, the process D2000 KOM is attempting to connect to the next address in the list.
Note 1: All IP addresses and ports must be defined stepwise for one station (i.e. at first "Alternate Server 1", "Alternate Port 1" and then "Alternate Server 2", "Alternate Port 2").
Note 2: These parameters are obsolete, since it's possible to define several IP addresses in the configuration of the line (separated by comma or semicolon, e.g. 10.0.0.1;10.0.0.2). 		- -
B-Alternate Server 1/
B-Alternate Port 1/
B-Alternate Server 2/
B-Alternate Port 2/		 Can be used when the protocol IEC 870-5-104 is configured for a TCP redundant line. The meaning of the parameters is the same as for primary connection, but they are valid for the backup connection.
Note 1: All IP addresses must be defined stepwise for one station (i.e. at first "Alternate Server 1", "Alternate Port 1" and then "Alternate Server 2", "Alternate Port 2").
Note 2: These parameters are obsolete, since it's possible to define several IP addresses in the configuration of the line (separated by comma or semicolon, e.g. 10.0.0.1;10.0.0.2). 		- -
Command Confirm Confirmation of control ASDU.
If Command Confirm=0, the process D2000 KOM is not waiting for confirmation of control ASDU from the partner station using backward sending ASDU with other CauseOfTransmission, ASDU is consider to be confirmed, when there is received a packet containing corresponding ReceiveSequenceNumber.
If Command Confirm=1, the process D2000 KOM is waiting for confirmation with CauseOfTransmission=7 (Activation Confirmation).
If Command Confirm=2, the process D2000 KOM is waiting for confirmation with CauseOfTransmission=10 (Activation Termination).
If Command Confirm=3, the process D2000 KOM waiting for confirmation with CauseOfTransmission=7 or 10 (if both of them are received, only the first of them is taken into account).
Having received corresponding confirmation means that writing is finished (the Transient attribute of written value is evaluated and the "Wait Timeout Tn" timeout stops elapsing).
If there is received confirmation with other CauseOfTransmission, as the process D2000 KOM expects for, it will be ignored.
Writing is successful, if the received ASDU contains the P/N bit set to 0. Otherwise, writing is unsuccessful.
Value from received ASDU is backwardly written into particular I/O tag and is sent to the system. E.g. if an ASDU of type 50 (short floating point) with the value of 1200.0 is sent and the partner station sends an ASDU of type 50 as reply, P/N bit=0, value of 999.0 (e.g. due to physical limitations of the given parameter) as a response, then the value is to be send by process D2000 KOM to the D2000 system. 		- 1
The parameters are intended for configuration of communication station for communication between two D2000 systems with using ASDU 252 - D2000 Unival (Ipesoft's implementation). more ...
Debug Input A mask for debug levels of input data. The meaning of bits is as follows:
  • 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
 - 0
Debug Output A mask for debug levels of output data. The meaning of bits is as follows:
  • 1.bit - balanced mode: displays a number of outgoing values during General Interrogation
  • 2.bit - displays all outgoing values
 - 0
End of initialization Extension for ABB MicroScada: If End of initialization=1, having received ASDU 70 (End of initialisation) resends Interrogation Command and/or Counter Interrogation Command. - 0
Force Master Time If Force Master Time=True, then the process D2000 KOM will accept ASDU 103 (Clock synchronisation command) with CauseOfTransmission=6 [Activation] or 3 [Spontaneous] from the server and saves the time difference between server's time and its time. If CauseOfTransmission=6, it replies with CauseOfTransmission=7 [Activation Confirmation].
Then time of all values, which are received with timestamps, is decreased by this difference, i.e. a correction to the time of D2000 is made.
The parameter allows to solve the problem when some values from server are received with the timestamps and others without timestamps and times from D2000 and server differ. In this case without parameter Force Master Time=True the values received without timestamps are specified by D2000 time and the values with the timestamps are specified by the server time. With parameter Force Master Time=True the time, sent by server, is corrected to D2000 time using the time difference, which is computed from the received ASDU 103 (Clock synchronisation command). 		- False
Force Slave Time Extension for ABB MicroScada: If Force Slave Time=True, then the process D2000 KOM will accept ASDU 103 (Clock synchronisation command) with CauseOfTransmission=6 [Activation] or 3 [Spontaneous] from the server and saves the time difference between server time and its time. If CauseOfTransmission=6, it replies with CauseOfTransmission=7 [Activation Confirmation].
Then all values, which are received with no timestamps, are to be marked by the current time plus time difference (if the station is not configured to use the communication computer time).
The parameter Force Slave Time allows to solve the problem, that having sent ASDU 100 or 101 there are sent ABB MicroScada values with no timestamps, but they are sent with the time stamps during the communication - problems can occur, when there are not synchronized the times of the MicroScada and the D2000 system. 		- False
GI Send New If GI Send New=True, then the process D2000 KOM after receiving the command General Interrogation sends also values with more recent times than is the time when the command is received. The value of the parameter GI Send New must be True to send values with more recent times using the command General Interrogation. - False
Ignore Control Field 3 bit 0 Determines behaviour, when ASDU contains Control Field with lowest bit (1) of the 3rd byte set.
  • 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
The feature can be used when creating a redundant TCP connection (TCP Redundant line + IEC 870-5-104 protocol). Hot server should send ASDU with the lowest bit of the 3rd Control Field byte set to 0, standby server should send ASDU with the lowest bit of the 3rd Control Field byte set to 1. 		- False
Ignore Invalids on Interrogation Balanced mode: if this parameter is set on a station, the process D2000 KOM will not send as a reply for ASDU 100 and 101 (Interrogation / Counter interrogation command) values of I/O tags which are Invalid or Unknown. Parameter can be used e.g. when controlling, if sending Invalid values causes breakdown of control. - False
Ignore Tests Determines behaviour, when ASDU contains bit 8 (test) set in CauseOfTransmission.
  • 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
The feature can be used for creating a redundant TCP connection (TCP Redundant line + IEC 870-5-104 protocol). Hot server should send ASDU with the Test bit=0, standby server should send ASDU with the Test bit=1. 		- 0
Ignore Unknown Addresses If Ignore Unknown Addresses=TRUE, the process D2000 KOM will not show an error on its console or write it into log files in case that incoming value has the address not matching any of the addresses of I/O tags defined in the D2000 system. - False
Implicit Interrogation Balanced mode: After connecting to the IEC104 server, the process D2000 KOM sends the values of all variables without waiting for ASDU 100 or 101 [Interrogation/Counter Interrogation Command] requests. - False
Interrogation Covers Counter Interrogation Balanced mode: As a reply to Interrogation, also values of I/O tags configured as ASDU 15, 16, 37 (Integrated Totals) are sent. (They are normally requested by ASDU 101 [Counter Interrogation].) - False
Interrogation WithOut Timestamps If Interrogation WithOut Timestamps=True, then values sent as a response to ASDU 100 [Interrogation Command] in balanced mode will be sent as ASDUs without timestamps.
For example instead of ASDU 2 (Single-point information with time tag) or ASDU 30 (Single-point information with time tag CP56Time2a) ASDU 1 (Single-point information) will be sent.
This behaviour is suitable in the situation when the values have been invalidated as a result of communication error and after the communication is reestablished the values come with old timestamps which causes problems in archive (if the values change only rarely, calculated archives depending on them will be also invalid till a new value arrives). 		- False
K Sending window size i.e. number of I-frames sent by the process D2000 KOM without receiving a confirmation (S-frame or I-frame). According to the standard, the default value is 12. - 12
LFC History

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.

- 0
Maximum Time Difference Maximum acceptable time difference (in hours) between the time of received data and the time of process D2000 KOM. If partner station sends a value with a timestamp older or latter then MDT hours, the value is to be ignored and an error report is to be generated into the line's trace file. If the parameter Maximum Time Difference is a negative value (e.g. Maximum Time Difference=-5), there is used its absolute value and the system tag SystemError is generated as well. If the parameter's value is zero, the time difference is not to be checked. hrs 0
No Flags If the parameter is True, then the status bit of incoming ASDUs is ignored and not saved into the flags FA...FH. Flags of output I/O tags are also ignored and they not set the status bit. - False
Order of IC Order of sending ASDU 100 [Interrogation Command] during connection initialization. If OIC<OCIC, ASDU 100 will be send before ASDU 101. If OIC=0, ASDU 100 will not be sent. The parameter can be set extra for each station. - 1
Order of Counter IC Order of sending ASDU 101 [Counter Interrogation Command] during connection initialization. If Order of IC < Order of Counter IC, ASDU 101 will be sent before ASDU 100. If Order of IC=0, ASDU 101 will not be sent. The parameter can be set extra for each station. - 2
Ping Count Number of repetitions, after which the IP address not responding to ping is known as non-functional.
See the parameter Ping TimeOut. 		- 3
Ping TimeOut If the parameter is other than zero, then defines the timeout (in milliseconds) of server response for ping (ICMP echo) packet. In the background, the process D2000 KOM sends ping packets to all defined IPs - Line IP address and Alternate Server 1, Alternate Server 2, B-Alternate Server 1, B-Alternate Server 2. If some of the addresses does not response for Ping Count-times, it is designated as non-functional. If the line is connected to this IP address, the connection is terminated. New connection is established just to a functional IP address. If the parameter Ping TimeOut=0, sending ping packet to IP addresses is disabled. ms 0
Post start delay A delay between receiving StartDT Con response and sending Interrogation Command and/or Counter Interrogation Command in the initialisation phase. ms 0
Pre Reconnect Delay A delay before connecting and reconnecting (after starting the process D2000 KOM and after communication break-up). ms 0
Send sequence number Initial Send sequence number. According to the standard, having established the connection the Send sequence number is set to 0, other than zero could be appropriate e.g. for testing. - 0
Smart Redundancy Minimum Number of values that must be identical in the Smart Redundancy Minimum mode to consider the connections synchronized. The following parameters are taken into account:
  • I/O tag and station addresses
  • value
  • time
  • flags (FA..FH)
 - 5
Smart Redundancy Mode Can be used for TCP Redundant line as alternative to Ignore Tests=1 or Ignore Control Field 3 bit 0=1. The process D2000 KOM assumes that the identical values go via the both connection of the TCP Redundant line in the same order. The process D2000 KOM is attempting to synchronize the connections. If the D2000 KOM process receives a number of identical values defined by the parameter Smart Redundancy Minimum, data are synchronized. After synchronisation is done, the value that comes earlier is taken into account, the same value via the other connection is ignored.
When the TCP connection is broken or two different values comes, the synchronisation is broken.
Compared to detection hot/standby partner by means of Ignore Tests/Ignore Control Field 3 bit 0, an advantage is that after communication failure with the hot server, there is no data loss, because the communication is still working with the standby partner and attempting to recover the connection with the hot server.
Having recovered the connection (if the second connection is working), there are ignored the values which are acquired by the command General Interrogation. 		- False
Standby Keep Open If True, after changing the status of process D2000 Server (the process D2000 KOM is connected to) from Hot into Standby state (redundant system), connection with the server will not be closed. - False
Standby Set Control Field If TRUE, after changing the status of process D2000 Server (the process D2000 KOM is connected to) from Hot to Standby state (in the redundant system), the lowest bit of the 3rd Control Field byte of information APDUs (APDU containing data or commands) will be set to 1 instead of the standard value of 0. The behaviour does not strictly follow the standard and we recommend you to use the parameter Standby Set Test Bit instead of this parameter if it is possible. - False
Standby Set Test Bit If True, the Cause Of Transmission will have a Test bit set if the process D2000 KOM is connected to Standby server (redundant system) or is a passive instance. - False
Standby Write Values If True, after changing the status of process D2000 Server (the process D2000 KOM is connected to) from Hot into Standby state (redundant system), there will be sent new values. - False
Station Communication Error Number of unsuccessful connection attempts after the communication failure after which the station status is changed to St_CommErr. For redundant lines, the communication must be either failed on both TCP connections or only a TCP connection to standby-server must be established (see the parameters Ignore Control Field 3 bit 0 and Ignore Tests), i.e. data from the server are ignored. - 2
Station Hard Error The status of all stations on line is changed into the state St_HardErr if the following conditions are met:
  • 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.
 - 5
Stop Data Confirm Ignored Workaround due to MetsoDNA server error: after connecting to IEC870-5-104 server from the firm Metso, the server sends a U-frame STOPDTcon (thereby confirms interruption in sending data). If the parameter Stop Data Confirm Ignored is True, this frame will be ignored and the communication will continue. Without the parameter Stop Data Confirm Ignored, the connection will be aborted. - False
Strict Redundancy Connection Signalisation Determines behaviour, when the protocol is used for TCP Redundant line
  • 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
 - False
Tcp Keep Init The parameter is implemented for use on OpenVMS platforms only. If it is other than zero, then defines the timeout (in seconds) for opening a new connection to server. For OpenVMS, the default value is 75 seconds, for Windows it is 20 seconds. When timeout expires, connect procedure returns error. - 0
Tcp No Delay Setting Tcp No Delay parameter causes low level socket option TCP_NODELAY being set, thus turning off default packet coalesce feature. - False
W Number of received I-frames, after which the process D2000 KOM sends a S-frame confirmation. According to the standard, the default value is 8. The relation W < K must be true, the standard recommends W = 2/3 * K. - 8
Wait Timeout T1 Timeout for receiving the confirmation of a sent I-frame (either confirmation within the I-frame or the S-frame itself) or a U-frame. If the process D2000 KOM does not get the confirmation in the time Wait Timeout T1, it closes the TCP connection. According to the standard, the Wait Timeout T1 default value is 15000 ms. ms 15 000
Wait Timeout T2 Timeout for sending the confirmation of a received I-frame. Wait Timeout T2 < Wait Timeout T2. If other I-frame (which confirms the received I-frame) is not sent in the time Wait Timeout T2 since the I-frame was received, so the process D2000 KOM sends a S-frame confirming the received I-frame to the partner. According to the standard, the Wait Timeout T2 default value is 10000 ms. ms 10 000
Wait Timeout T3 Timeout for sending test frames (U-frame TEST ACT). If no data are sent in any direction for a long time, an U-frame TEST ACT will be sent to the process D2000 KOM after expiration of the Wait Timeout T3 time and there is expected (in the Wait Timeout T1 time after sending) receiving a U-frame TEST CON. If the Wait Timeout T3 on the partner side is set to a lower value, it sends the test frames and the process D2000 KOM reply them. According to the standard, the Wait Timeout T2 default value is 20000 ms.
Setting the value to 0 disables sending test frames. 		ms 20 000
Wait Timeout No answer Timeout for receiving the confirmation of a sent value. Receiving e.g. S-frame with RSN (Receive Sequence Number) confirming, that the other party received previous I-frame doesn't mean, that the I-frame was processed. In the Wait Timeout Tn, the process D2000 KOM waits for receiving the response (e.g. after sending ASDU with TypeIdentificator=45 [Single Command] with CauseOfTransmission=6 [Activation] there is expected receiving Single Command with CauseOfTransmission=7 [Activation Confirmation].
After the expiration of the Wait Timeout Tn, the process D2000 KOM closes the TCP connection. 		ms 60 000

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.

Tell commands

Table 4

Command Syntax Description
STCOMMAND STCOMMAND StationName DISCONNECT Tell command closes immediately the active TCP connections of the communication line (a parent of  "StationName"). Then the connection is restarted and re-connected.

Examples of configurations

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

Server settings

  • line: TCP/IP-TCP (Host ALL, port 2404)
  • protocol: IEC 870-5-104 Server
  • parameters: none

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.

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;

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.

Servers' settings

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

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.

Servers' settings

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

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.

I/O tag configuration

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.

Literature

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Document revisions

  • 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

Related pages:

Communication protocols

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