IEC 870-5-104 Server communication protocol

Supported device types a versions  
Communication line configuration
Communication station configuration
I/O tag configuration
Literature
Document revisions

Supported device types and versions

Communication supports reading and writing data by means of the IEC870-5-104 communication protocol operating on the basis of TCP network communication. D2000 system works in the mode IEC 870-5-104 server (slave), that is enable to communicate with N clients (masters). Implementation is according to the standard IEC870-5-104 as follows:

• initial Originator ASDU address is 1 byte, it is defined as line number.
• ASDU address is 2 bytes, it is defined as station address. For each station on one line, there must be defined different ASDU address.
• Cause of transmission is 2 bytes (it also contains Originator ASDU address)
• Information object address = 3 bytes, it is defined as I/O tag address.
• There are implemented the following ASDU types in the direction of logging (from D2000 system to control station and also vice-versa in balanced mode):

Table nr. 1

Note: For setting individual bites of the byte that inform us on quality (SIQ for ASDU 1,2,30; DIQ for ASDU 3,4,31; QDS for ASDU 5..14,20,32..36), there are used the flags FLA (0.bit),FLB (1.bit) ..FLH (7.bit).

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 bites 0..4, FLF=CY bit, FLG=CA bit, FLH=IV bit

Except the bites, which are set directly by a value (e.g. for ASDU 1, the 0.bit is not set by the flag FLA but by the value of output I/O tag).
If there is the attribute Invalid is set to a new value, the higher bit (IV) will be set in the status byte of all ASDU (except ASDU 21 not containing it).

* - Status is taken as low 2 bytes, Status change detection is taken as high 2 bytes of 32-bite integer.

There are implemented the following ASDU types in the direction of control (from control station to D2000, also the opposite direction in balanced mode):

Table nr. 2

Bites of "status" byte (SCO fro ASDU 45,58; DCO for ASDU 46,59; RCO for ASDU 47,60; QOS for ASDU 48..50,61..63) causes setting the flags FLA (0.bit),FLB (1.bit) ..FLH (7.bit) with exception for the bites, which are directly set by the value of a variable ( SCO bit 0, DCO a RCS bity 0-1). After receiving an response (positive/negative), the flags FLA..FLH are set according the bites of "status" byte.

When writing values, the value of 6 [Activation] is waited as CauseOfTransmission. Response of control station depends on the setting of the parameter CMDC. Originator ASDU address will be used the same as in the received command.

Establishing connection:

- process D2000 KOM is waiting on TCP port and, after establishing a connection, is waiting for sending the U-frame StartDT Act from the client. It is waiting for StartDT Con as a response (it is possible to send TestFrame before StartDT Act)
- if the parameter EOI is set for the process D2000 KOM, there is sent ASDU 70 [End of initialization], the initial address (set a line number) is used as  Originator ASDU address
- if the parameter Synchronisation period (the tab Time parameters) for some station is different from 0, ASDU 103 [Clock synchronisation command] with CauseOfTransmission= 6 [Activation] is sending in given period. The initial address (set as line number) or Originator ASDU of the last received ASDU 1000 or 101 is used as Originator ASDU address.
- process D2000 KOM sends new values acquired from the process D2000 Server  for variables with ASDU 1..14, 20, 21, 30 .. 36 to a client, which sent ASDU 100 [Interrogation Command] and new values for variables with ASDU 15,16,37 to a client, which sent ASDU 101 [Counter Interrogation Command]
- process D2000 KOM accepts time synchronisation using ASDU of 103 type [Clock synchronisation command] with CauseOfTransmission=6 [Activation] or 3 [Spontaneous]. If CauseOfTransmission= 6, it responds in dependence on setting the parameter CMDC, if CauseOfTransmission= 3, it does nOt response.
- process D2000 KOM responses to received commands (ASDU 45..51, 58..64) with CauseOfTransmission= 6 [Activation] in dependence on setting the parameter CMDC.

Originator ASDU address (OA): initial OA is set as TCP line number in the configuration. The address will be used for optimum sending the ASDU 70 [End of initialization] at the beginning of connection and always when sending new values.
After receiving ASDU 100 or 101, there are sent current values of all output I/O tags (with no attribute Invalid set) with the same OA as contained in ASDU 100 or 101.
As responses to received commands (ASDU 45..51, 58..64), there are sent confirmations with the same ASDU as contained in the received command.

D2000 system also supports the balanced mode. In the mode, the task of controlled and control stations is changed. That time, D2000 system sends commands and ASDU 100/101. The balanced mode may be used only when is supported by partner station. An advantage is that D2000 system sends ASDU 100 [Interrogation Command] a 101 [Counter Interrogation Command] and gets the status of output I/O tags (configured as ASDU 1-40) after disconnection and re-establishing the connection. It is suitable to configure single-shot commands as ASDU 45 - 64; they are not repeated after re-establishing the connection.

Writing an output I/O tag:
When writing IEC 104 values (ASDU 1-40), there are valid the rules of server protocols.
When writing IEC 104 values (ASDU 45-64) in the balanced mode, ASDU is considered to be confirmed (away from the state Transient) in dependence on the parameter CMDC. If the connection to a client is lost when writing, the writing success depends on the parameter PW.

Communication line configuration

• Communication line category: TCP/IP-TCP
• TCP Parameters
  • Required to define the server parameters
  • Host: string containing at most 80 characters – name of the network interface in form of INET (name or numerical address a.b.c.d, e.g. 192.168.0.1) using of which the process D2000 KOM will receive clients. If the name is ALL, tge process  D2000 KOM will wait on all network interfaces of the computer, where is running.
  • Port: TCP port number (0..65535), where the process D2000 KOM is waiting.
  • Line number: will be used as Originator ASDU address (1 byte, 0-255).

Note: Starting from D2000 version 7.02.004 the flags FLA to FLP are used during setting of the value of communication line to inform about connected active clients. Active client is a client who after establishing the connection sent U-frame StartDT Act, i.e. asked for sending the data. The first connected active client will cause change of flag FLA to TRUE, the second flag FLB etc upto flag FLP and continuing with the flag FLA. If the client sends U-frame StopDT Act (requesting the server to stop sending data) or disconnects, the value of its flag will be changed to FALSE.

Communication station configuration

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

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 +).

Station protocol parameters

The following parameters can be defined as station protocol parameters:

Table nr. 3

String containing the protocol parameters is being defined as follows:

Keyword=value;Keyword=value; ...

Example:

WTn=10000;WT3=25000;OCIC=0;

If there is used a keyword with an invalid value in the initialization string, there will be used corresponding default value according the table. Defined parameters, except for OIC, OCIC and FST are valid for the entire line - i.e. it is enough to define them for one station on the line.

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.
• For particular type of output tag (Ao, Dout, Co) it is necessary to set an ASDU type, that has to be used, see the table 2 and also the table 1 in the balanced mode.
• Archive for providing old values: if client requires archive values using ASDU 250, the server sends:
  1. values of archived I/O tag, which are defined in this entry field
  2. if the entry field is not defined, values of archived I/O tag, that are directly archived by the I/O tag
  3. if the archived I/O tag does not exist, values of the I/O tag, that is archived by the control object of the I/O tag
  4. if the object doesn't exist (or the archive is not available), the server returns an error.
  Definition of an I/O tag allows e.g. to set sending 10-minute averages instead of sending all changes of the I/O tag.

Literature

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Document revisions

• Ver. 1.0 – 5.2.2004
• Ver. 1.1 – December 1st 2004: extension - support of balanced mode