Read Cycle - Siemens SIMATIC TeleControl DNP3 Configuration Manual

Types of transmission and event classes
The following types of transmission are possible:
● Transfer after call (class 0)
The current value of the data point is entered in the image memory. New values of a data
point overwrite the last stored value in the image memory.
After being called by the communications partner, the current value at this time is
transferred.
● Triggered
Data points are configured as an event using a triggered type of transmissopn. The
values of these data points are entered in the image memory and also in the send buffer.
The values of an event are saved as soon as the configured trigger conditions are met.
The following event classes are available:
– Every value triggered
– Current value triggered
For information on the different trigger types, see section "Trigger" tab (Page 116).
3.20.6

Read cycle

Input data points are assigned to the read cycle of the CPU in the data point configuration in
the "General > Read cycle" tab.
Structure of the CPU scan cycle
The cycle with which the transferring module (TIM) scans the memory area of the CPU is
made up of the following phases:
● High-priority read jobs
(Fast cycle)
For all data points with the assignment "Fast cycle" the PLC tags are read in every scan
cycle.
As a rule, it is sufficient to assign only data to be acquired quickly, such as alarms and
contact changeover messages as well as command, setpoint and parameter objects for
the 1oon check, to the fast cycle.
For information on the 1oon check, see the Glossary.
Configuration - DNP3
Configuration Manual, 11/2018, C79000-G8976-C508-01
Each value change is entered in the send buffer in chronological order.
Only the last, current value is entered in the send buffer. It overwrites the value stored
there previously.
Configuration
3.20 Configuring data points
115