Configuration
4.18 Data points
CP 1243-8 IRC
148 Operating Instructions, 02/2018, C79000-G8976-C385-03
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:
●
The values of input data points with the scan priority "High-priority" are read in every scan
cycle.
●
Some of the values of input data points with the scan priority "Low-priority" are read in
every scan cycle.
The number of values read per cycle is specified for the CP in the "Communication with
the CPU" parameter group with the "Max. number of read jobs" parameter. The values
that exceed this value and can therefore not be read in one cycle are then read in the
next or one of the following cycles.
●
In every cycle, the values of a certain number of unsolicited write jobs are written to the
CPU. The number of values written per cycle is specified for the CP in the
"Communication with the CPU" parameter group with the "Max. number of write jobs"
parameter. The values whose number exceeds this value are then written in the next or
one of the following cycles.
●
This is the waiting time between two scan cycles. It is used to reserve adequate time for
other processes that access the CPU via the backplane bus of the station.
Data points are configured as a static value or as an event using the "Type of transmission"
parameter:
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