Configuration
3.20 Configuring data points
Configuration - DNP3
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Configuration Manual, 11/2018, C79000-G8976-C508-01
The image memory, the process image of the module
The image memory is the process image of the TIM. All the current values of the configured
data points are stored in the image memory. New values of a data point overwrite the last
stored value in the image memory.
The values are sent only after a query by the communications partner - see below "Transfer
after call" in the "Types of transmission" section - or along with a message from the send
buffer that needs to be transferred immediately.
The send buffer
The send buffer of the TIM is the memory for the individual values of data points that are
configured as an event. You will find the size of the send buffer in the manual of the relevant
module.
The capacity of the send buffer is divided up equally for all enabled partners.
If the connection to a communications partner is interrupted, the individual values of the
events are retained in the buffer. When the connection returns, the buffered values are sent.
The frame memory operates chronologically; in other words, the oldest frames are sent first
(FIFO principle).
If a frame was transferred to the communications partner, the transferred value is deleted
from the send buffer.
If frames cannot be transferred for a longer period of time and the send buffer is threatening
to overflow, the response is as follows:
●
If the send buffer reaches a fill level of 80%, a warning message is output.
●
If the fill level of the send buffer reaches 100%, no more values are saved until the fill
level falls below 100% again.
Saving the data point values
As a rule, the values of data points are stored in the image memory of the moodule and
transferred only when queried by the communications partner.
Events are also stored in the send buffer and can be transferred unsolicited.
Data points are configured as a static value or as an event using the "Type of transmission"
parameter (see below):
●
Static value (no event)
Static values are entered in the image memory (process image).
Static values correspond the following type of transmission "Transfer after call (class 0)".
●
Event
The values of data points configured as an event (triggered type of transmission) are also
entered in the image memory of the module. The values are also entered in the send
buffer.
