Read Cycle - Siemens ET 200SP Operating Instructions Manual

Configuration and operation
4.5 Telecontrol communication (CP 1542SP-1 IRC)
DNP3
On a CP, data point indexes must be unique within each of the following object groups:
● Binary Input / Binary Input Event
● Binary Output / Binary Command
● Counter / Counter Event
● Analog Input / Analog Input Event
● Analog Output
● Octet String / Octet String Event
Indexes of two data points in different object groups can be identical.
IEC
The data point indexes must be unique in a CP.
Data point indexes assigned twice are indicated as errors in the consistency check and
prevent the project being saved.
4.5.7.6

Read cycle

Priority of the data points
The cyclic reading of the values of input data points from their assigned PLC tags on the
CPU can be prioritized.
Less important input data points do not need to be read in every CPU scan cycle. Important
input data points, on the other hand, can be prioritized for updating in every CPU scan cycle.
You can prioritize the data points in STEP 7 in the data point configuration in the "General"
tab with the "Read cycle" parameter. There you will find the two following options for input
data points:
● Fast cycle
● Normal cycle
The data points are read according to the method described below.
Structure of the CPU scan cycle
The cycle (including the pause) with which the CP scans the memory area of the CPU is
made up of the following phases:
● High-priority read jobs
The values of input data points with the scan priority "High-priority" are read in every scan
cycle.
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CP 1542SP-1, CP 1542SP-1 IRC, CP 1543SP-1
Operating Instructions, 01/2017, C79000-G8976-C426-03