Siemens SIMATIC PCS 7 System Manual page 123

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
T
Note
If T
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 126), calculate the share of the maximum inhibit time for priority classes > 15 that
is required by the user program (T
Note
If T
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
Example of the calculation of T
In the next steps, we take an existing system configuration and define the maximum
permitted time span of an update, during which the operating system does not execute any
programs or I/O updates.
There are two DP master systems and one IO subsystem: DP master system_1 is connected
via the DP interface of the CPU, and DP master system_2 is connected to the CPU via an
external DP master interface. The IO subsystem is connected via the integrated Ethernet
interface.
1. Based on the bus parameters in STEP 7:
T
T
T
T
2. Based on the configuration in STEP 7:
T
T
3. Based on the technical data of the DP slaves used:
T
T
CPU 410-5H Process Automation/CPU 410 SMART
System Manual, 09/2014, A5E32631667-AB
= 50 ms + min. I/O retention time [2]
P15_OD
> T , stop the calculation here. Possible remedies are shown below the
P15_OD P15_HW
> T , stop the calculation here. Possible remedies are shown below the
P15_AWP P15_HW
MAX (T , T
P15 = P15_AWP P15_OD
P15
= 25 ms
TR_1
= 30 ms
TR_2
= 100 ms
DP_UM_1
= 80 ms
DP_UM_2
= 8 ms
max_Akt
= 110 ms
PN_UM
= 30 ms
SLAVE_UM_1
= 50 ms
SLAVE_UM_2
):
P15_OD
).
P15_AWP
) [3]
Link-up and update
8.3 Time monitoring
123