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Link-up and update
8.3 Time monitoring
Decisive factors for determining this time are the process status and the communication load
in your system. This can be understood as the absolute load or as the load relative to the
size of your user program. You may have to adjust this time.
Calculation of the maximum cycle time extension
Use the following formula:
Maximum cycle time extension =
10 x (maximum inhibit time for priority classes > 15)
Decisive factors for determining this time are the process status and the communication load
in your system. This can be understood as the absolute load or as the load relative to the
size of your user program. You may have to adjust this time.
8.3.3
Performance values for link-up and update
User program share T
The user program share T
calculated using the following formula:
T
P15_AWP
The table below shows the derived times for some typical values in work memory data.
Table 8- 3
Work memory data
500 KB
1 MB
2 MB
5 MB
10 MB
The following assumptions were made for this formula:
● 80% of the data blocks are modified prior to delaying the interrupts of priority classes >
15.
In particular for fail-safe systems, this calculated value must be more precise to avoid any
timeout of driver blocks (see section Determining the monitoring times (Page 113)).
● For active or queued communication functions, allowance is made for an update time of
approximately 100 ms per MB in the work memory occupied by data blocks.
Depending on the communication load of your automation system, you will need to add or
deduct a value when you set T
120
of the maximum inhibit time for priority classes > 15
P15_AWP
P15_AWP
in ms = 0.7 x size of DBs in work memory in KB + 75
Typical values for the user program part
of the maximum inhibit time for priority classes > 15 can be
T
P15_AWP
220 ms
400 ms
0.8 s
1.8 s
3.6 s
.
P15_AWP
CPU 410-5H Process Automation/CPU 410 SMART
System Manual, 10/2013, A5E32631667-AA
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