General
Network cycle time: multitasking application
Introduction
Convention
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.
The following table shows all the parameters involved in the calculation of the network cycle time.
Parameter
P max
P min
T max
T min
R
NE max
NE min
NE_Equip
TCR_T max
TCR_T min
Definition
Value of the largest task period (MAST or FAST)
Value of the smallest task period (MAST or FAST)
Task with period P max
Task with period P min
Ratio between the periods (This ratio must be a whole number; it will be rounded off to the nearest whole number if necessary).
Number of devices from the same family configured in T max
Number of devices from the same family configured in T min
Equivalent number of devices from the same family
Network cycle time for the task T max
Network cycle time for the task T min
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General
Calculation algorithm
To calculate the network cycle time, the algorithm is as follows:
Stage
1
Description
Calculation of R
2
3
4
R =
Pmin
Calculation of NE_Equip (for each device family)
NE_Equip =
( (
R
×
NEmin
)
+ NEmax
)
Calculation of TCR_T max
TCR_Tmax = 1,45 +
∑
(
K
×
NE_Equip
)
Calculation of TCR_T min
TCR_Tmin =
R
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General
Value of coefficient K
Coefficient K will be defined as follows:
1,5
0,4
0,6
1,5
0,4
0,6
1,5
1,3
1,5
0,6
0,6
0,6
1,5
1,5
0,6
Coefficient K
0,5
0,9
0,4
0,6
Family
TBX
TBX
Momentum
Momentum
ATV-16
ATV-58
CCX 17
CCX 17-32
TSX 37/57
AS-i gateway
Magelis
STD_P
STD_P
STD_P
ADVANTYS STB NFP 2212 02
ADVANTYS STB NFP 2212 08
ADVANTYS STB NFP 2212 32
Lexium 15
Lexium 17D
All
All
All
All
FRD
FSP
FED
All
All
Device
Discrete
Analog
Discrete
Analog
All
All
All
All
All
TSX SAP 10
Interpretation of the results
To refresh the inputs/outputs on the bus, the following constraints are imposed: z z
For the periodic tasks in controlled mode, the network cycle time of the task must be less than the task period.
For the periodic tasks in free mode, the network cycle time of the task must be less than the task watchdog.
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