Link-up and update
8.3 Time monitoring
CPU 410-5H Process Automation
System Manual, 09/2014, A5E31622160-AB
129
5.
Based on the technological specifications of your system, determine the following:
–
Maximum permissible time during which there is no update of your I/O modules
(referred to below as T
PTO
).
6.
Based on your user program, determine the following:
–
Cycle time of the highest-priority or selected (see above) cyclic interrupt (T
WA
)
–
Execution time of your program in this cyclic interrupt (T
PROG
)
7.
For each DP master system this results in:
T
P15
(DP master system) = T
PTO
- (2 x T
TR
+ T
WA
+ T
PROG
+ T
DP_UM
+ T
SLAVE_UM
) [1]
8.
For for each IO subsystem, this results in:
T
P15
(IO subsystem) = T
PTO
- (2 x T
max_Akt
+ T
WA
+ T
PROG
+ T
PN_UM
+ T
Device_UM
) [1]
Note
If T
P15
(DP master system) < 0 or T
P15
(IO subsystem) < 0, stop the calculation here.
Possible remedies are shown below the following example calculation. Make appropriate
changes and then restart the calculation at 1.
9.
Select the minimum of all T
P15
(DP master system, IO subsystem) values.
This time is referred to below as TP15_HW.
10.
Determine the share of the maximum inhibit time for I/O classes > 15 that is required by
the minimum I/O retention time (T
P15_OD
):
T
P15_OD
= 50 ms + min. I/O retention time [2]
Note
If T
P15_OD
> T
P15_HW
, stop the calculation here. Possible remedies are shown below the
following example calculation. Make appropriate changes and then restart the calculation
at 1.
11.
Using the information in Chapter Performance values for link-up and update
(Page 133), calculate the share of the maximum inhibit time for priority classes > 15 that
is required by the user program (T
P15_AWP
).
Note
If T
P15_AWP
> T
P15_HW
, stop the calculation here. Possible remedies are shown below the
following example calculation. Make appropriate changes and then restart the calculation
at 1.
12.
The recommended value for the maximum inhibit time for priority classes > 15 is now
obtained from:
T
P15 =
MAX (T
P15_AWP
, T
P15_OD
) [3]