General
Example of calculating the network cycle times of a multitasking application
Introduction
Convention
Algorithm
The configuration of the example is as follows: l l
Task periods: l l
MAST: 60 ms
FAST: 15 ms
The configuration comprises: l 6 discrete TBXs configured in the MAST task and 4 discrete TBXs configured in the FAST task, l l l
6 analog TBXs configured in the MAST task and 4 analog TBXs configured in the FAST task,
6 discrete Momentums configured in the MAST task and 4 discrete
Momentums configured in the FAST task,
6 analog Momentums configured in the MAST task and 4 analog Momentums configured in the FAST task, l l l
Depending on the configuration, the application of conventions involves:
P max
= 60 and P min
= 15
T max
= T
MAST
and T min
= T
FAST
TCR_T max
= TCR_T
MAST
and TCR_T min
= TCR_T
FAST
The following table shows the algorithm:
Stage
1
2
3
4
Description
Calculation of R
R = 60 / 15 = 4
Calculation of the equivalent number of devices
NE_TBX_TOR = (R * 4 + 6) = 22
NE_TBX_ANA = (R * 4 + 6) = 22
NE_MOMENTUM_TOR = (R * 4 + 6) = 22
NE_MOMENTUM_ANA = (R * 4 + 6) = 22
Calculation of the network cycle times TCR_T
MAST
TCR_T
MAST
= 1.45 + ((0.5 * 22) + (0.9 * 22) + (0.4 * 22) + (0.6 * 22))
TCR_T
MAST
= 54.25 ms
Calculation of the network cycle times TCR_T
FAST
TCR_T
FAST
= 54.25 / 4
TCR_T
FAST
= 13.56 ms
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Conclusions
General
The network cycle times of each equal: l l
TCR_T
MAST
= 55 ms,
TCR_T
FAST
= 14 ms.
The time period for MAST and FAST tasks are sufficient to refresh the inputs/ outputs.
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General
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