Siemens SIMATIC S7-400H System Manual page 163

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.
Assumin g two DP master systems and one IO subsystem are available: DP master
system_1 is connected to the CPU via the MPI/DP interface of the CPU, and DP master
system_2 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:
2. Based on the configuration in STEP 7:
3. Based on the technical data of the DP slaves used:
4. Based on the technical specifications of the PN devices used:
5. Based on the technological settings of your system:
6. Based on the user program:
7. Based on the formula [1]:
8. Based on the formula [1]:
S7-400H
System Manual, 03/2012, A5E00267695-11
P15
T = 25 ms
TR_1
T = 30 ms
TR_2
T = 100 ms
DP_UM_1
T = 80 ms
DP_UM_2
T = 8 ms
max_Akt
T = 110 ms
PN_UM
T = 30 ms
SLAVE_UM_1
T = 50 ms
SLAVE_UM_2
T = 20 ms
Device_UM
T = 1250 ms
PTO_1
T = 1200 ms
PTO_2
T = 1000 ms
PTO_PN
T = 300 ms
WA
T = 50 ms
PROG
T (DP master system_1)
P15
= 1250 ms - (2 x 25 ms + 300 ms + 50 ms + 100 ms + 30 ms) = 720 ms
T (DP master system_2)
P15
= 1200 ms - (2 x 30 ms + 300 ms + 50 ms + 80 ms + 50 ms) = 660 ms
T (IO subsystem)
P15
= 1200 ms - (2 x 8 ms + 300 ms + 50 ms + 110 ms + 20 ms) = 704 ms
Link-up and update
12.4 Time monitoring
163