Network Cycle Time: Multitasking Application
(Original Document)
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At a Glance
For a multitasking application with two periodic tasks, and if the devices are configured in each of the tasks, the value of the network cycle times depends on the configuration of the different tasks.
The cycle time values calculated with the following algorithm are the maximum values. The actual values are less than or equal to these values.
Convention
The following table shows all the parameters involved in the calculation of the network cycle time.
Parameter
Definition
Pmax
Value of the largest task period (MAST or FAST)
Pmin
Value of the smallest task period (MAST or FAST)
Tmax
Task with period Pmax
Tmin
Task with period Pmin
R
Ratio between the periods (This ratio must be a whole number; it will be rounded off to the nearest whole number if necessary).
NEmax
Number of devices from the same family configured in Tmax
NEmin
Number of devices from the same family configured in Tmin
NE_Equip
Equivalent number of devices from the same family
TCR_Tmax
Network cycle time for the task Tmax
TCR_Tmin
Network cycle time for the task Tmin
Calculation Algorithm
To calculate the network cycle time, the algorithm is as follows:
Phase
Description
1
Calculation of R
2
Calculation of NE_Equip (for each device family)
3
Calculation of TCR_Tmax
4
Calculation of TCR_Tmin
Value of Coefficient K
Coefficient K will be defined as follows:
Coefficient K
Family
Device
0.5
TBX
Discrete
0.5
TBX
Discrete Compact
0.9
TBX
Analog
0.5
TBX IP65
All
0.4
TBX IP67
All
0.4
Momentum
Discrete
0.6
Momentum
Analog
0.6
Momentum expert
170 AEC 920
0.6
Altivar
All
1.5
TSX 37/57
All
0.6
AS-i gateway
TSX SAP 10
1.5
Magelis
All
0.4
STD_P
FRD
0.6
STD_P
FSP
1.5
STD_P
FED
1.5
Lexium
All
0.6
Inductel
All
0.4
Advantys
2W
0.6
Advantys
8W
1.5
Advantys
32W
Interpretation of the Results
To refresh the inputs/outputs on the bus, the following constraints are imposed: