Dependency Of The User Program Scanning Time; Updating The S7 Timers - Siemens SIMATIC IM 151/CPU Manual

Cycle and Response Times
User Program Scanning Time:
The user program scanning time is made up of the sum of the execution times for
the instructions and SFCs called. These execution times can be found in the
Instruction List. You also have to multiply the user program scanning time by a
basic module-specific factor.
In the IM 151/CPU, this factor depends on the following:
Table 7-3

Dependency of the User Program Scanning Time

The number of modules inserted
The volume of data transferred via the
PROFIBUS-DP between the DP master and DP
slave (input data + output data)
The volume of data
communication
You can calculate the factor for your application approximately using the following
rule of thumb for the IM 151/CPU
1,1
+ 0.0055 x number of modules
+ 0.0022 x number of bytes transfered (PROFIBUS-DP)
+ 0.0011 x number of bytes obtained (direct communication)
= Multiplier for your user program
S7 Timers
The S7 timers are updated every 10 ms.
To include the S7 timers in the calculation of the cycle and response times of the
IM 151/CPU, multiply the number of active S7 timers by 8 µs.
Table 7-4

Updating the S7 Timers

Updating the S7 timers (every 10 ms)
7-4
Dependency
obtained
through direct
Sequence
0 to 63
0 to 128 bytes
0 to 256 bytes
IM 151/CPU
Number of simultaneously active
S7 timers 8 s
ET 200S Interface Module IM 151/CPU
Range
A5E00058783-01