Process Image Updating - Siemens SIMATIC IM 151/CPU Manual

Extending the Cycle Time
Note that the cycle time of a user program is extended by the following:
Time-controlled interrupt handling
Process interrupt handling (see also Section 7.3)
Diagnostics and error handling (see also Section 7.3)
Operating System Processing Time
The operating system processing time for the IM 151/CPU
(see Table 7-1).
The specified time does not include the execution of:
Test functions, e.g. monitor, modify
Functions: Load block, delete block, compress block
Communication
Table 7-1
Operating system processing time
Process Image Transfer Time
The table below contains the CPU times for process image updating (process
image transfer time). The specified times are "ideal" values that get increased by
interrupts that occur or by communication involving the CPU component of the
IM 151/CPU.
(Process image = PI)
The CPU time for process image updating is calculated as follows:
K + A = process image transfer time, in which K and A equal the following:
Table 7-2
K Base load
Q Bytes in the PI for the ET 200S I/O
ET 200S Interface Module IM 151/CPU
A5E00058783-01
Extending the Cycle by Nesting Interrupts
Sequence

Process Image Updating

Designation
Cycle and Response Times
takes 540 s to 1040 s
IM 151/CPU
540 s to 1040 s
Times in the IM 151/CPU
162 s
80 s per byte
7-3