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To set the 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), the flags A (0.bit), B (1.bit) .. H (7.bit) are used, except the bits, which are directly set by the variable value (SCO bit 0, DCO and RCS bits 0-1). Having received a response (positive/negative), the A .. H flags are set according to the bits of the "status" byte.
When sending commands (ASDU 45-64), the value of 6 [Activation] is sent as a CauseOfTransmission. The expected response from the controlled station depends on the Command Confirm parameter. There are the following possibilities:
- writing is successful if the packet with RSN confirming the SSN packet with the write command
- writing is finished, if there is a response with CauseOfTransmission=7 [Activation Confirmation] and/or with 10 [Activation Termination]. Success/failure depends on the setting of the P/N bit in CauseOfTransmission.
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For all the stations with a defined synchronization (see the article below), an ASDU type 103 [Clock synchronisation command] with CauseOfTransmission=6 [Activation] is sent, and a reply (depending on the Command Confirm parameter) is expected.
Then 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:
- reception of frames with ASDU 100 [Interrogation Command] and with CauseOfTransmission=7 or 10 (depending on the Command Confirm parameter)
- reception of frames with ASDU 101 [Counter Interrogation Command] and with CauseOfTransmission=7 or 10 (depending on the Command Confirm parameter)
- reception of current values of all I/O tags.
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The D2000 system also supports a balanced mode. In the this mode, the task of controlled and control stations is 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), the rules of server protocols apply to it.
The output tags, which are configured as ASDU 1-40, do not go through the Transient status (i.e. they are considered as if in the configuration of I/O tag, Output control tab, the I/O tag output mode is set to Command). The writing is considered to be successful if there is a connection with the server at the time of writing, otherwise, the writing is unsuccessful.
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- I/O tag address is mapped 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 table 1 and also table 2 in the balanced mode.
- For a particular type of output tag (Ao, Dout, Co), it is necessary to set an ASDU type, that has to be used, see table 2.
- Archive for providing historical values: if the client asks for historical values through ASDU 250, the server sends:
- the values of the historical value specified by this input entry field,
- if the input entry field is not filled, then the values of the historical value that archives the I/O tag,
- if the specified historical value does not exist, then the values of the I/O tag that archives the control object of the specified I/O tag,
- if the control object does not exist (or the archive is not available), the server returns an error.
- 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).
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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
- Ver. 1.2 – November 16th, 2023 (support for the Destination Column)
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