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Configuration (WBM)
4.20 Telecontrol
Processing of process data
Data points
When processing process data, the inputs and outputs are processed by the program and
saved in the address areas input, output and bit memory of the RTU. The individual
addresses are mapped and addressed as data points for the communication. The data
points are processed one-to-one in the control system.
In the IEC protocol, the data point corresponds to an information object.
Below you will find a table with the data types of the addresses and the assigned data point
types.
There are two classes of data points:
● Static data points
The values of these data points are saved in the image memory of the RTU.
A newly read in value of a tag overwrites the last value saved. The values are only
transferred after being called up by the communications partner.
● Events
Saving and transferring the events
The values of events are saved in the send buffer (frame memory). Note the overall size of
the send buffer, refer to the section Performance data (Page 32).
The send buffer works chronologically: The oldest data is sent first (FIFO principle) and
deleted from the send buffer if the transfer was successful.
If data cannot be transferred for a longer period of time and the send buffer is threatening to
overflow, the protocol-dependent response is as follows:
● Telecontrol Basic, ST7
The forced image mode
If the send buffer reaches a fill level of 80%, the RTU changes to the forced image mode.
New values from data points are no longer additionally saved but rather they overwrite
older existing values.
When the connection to the communications partner returns, the module changes back to
the send buffer mode as soon as the fill level of the send buffer has fallen below 50%.
● DNP3 / IEC
If a send buffer fill level of 100% is reached, no further values are saved until the fill level
falls below 100% again.
The saving of the values is triggered by configurable conditions, see the section "Trigger"
below.
The transfer of the events to the communications partner can be triggered immediately
(spontaneously) or after intermediate buffering. This is controlled by the "Transfer mode",
see below.
184
Operating Instructions, 09/2017, C79000-G8976-C382-04
RTU3030C
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