Siemens SIMATIC S7-400H System Manual page 114

Link-up and update
9.4 Time monitoring
Remedies if it is not possible to calculate T
If no recommendation results from calculation of the maximum inhibit time for priority classes
> 15, you can remedy this by taking various measures:
● Reduce the cyclic interrupt cycle of the configured cyclic interrupt.
● If T
● Increase the transfer rate on the affected DP master systems.
● Configure the DP/PA Links and Y Links in separate DP master systems.
● If there is a great difference in changeover times on the DP slaves, and so (generally) great
● If you do not expect any significant load caused by interrupts or parameter assignment in
● The time value T
If you reduce the time T
the update operation will be aborted due to a monitoring timeout.
Calculation of the maximum communication delay
Use the following formula:
Maximum communication delay = 4 x (maximum inhibit time for priority classes > 15)
Decisive factors for 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
Its is advisable to use the following formula:
Maximum cycle time extension = 10 x (maximum disable time for priority classes > 15)
Decisive factors for 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.
See also
Performance values for link-up and update (Page 115)
114
times are particularly high, distribute the slaves across several DP master systems.
TR
differences in T , distribute the slaves involved across several DP master systems.
PTO
the various DP master systems, you can also reduce the calculated T
20 % to 30 %. However, this increases the risk of a station failure in the distributed I/O.
P15_AWP
You can reduce it by taking the following measures, for example:
– Save data that changes often in different DBs from data that does not change as often.
– Assign the DBs a smaller length in wotk memory.
P15_AWP
P15
represents a guideline and depends on your program structure.
without taking the measures described, you run the risk that
times by around
TR
System Manual, 09/2007, A5E00267695-03
S7-400H