Operating System Processing Times Of The Cpus - Siemens SIMATIC S7-300 Series Reference Manual

Cycle and Reaction times
Calculation
The (longest) response time consists of the following:
S 2
Process image transfer time of inputs +
S 2
Process image transfer time of outputs +
S 2
Operating system execution time+
S 2
program execution time+
S 2
Bus runtime on the PROFIBUS-DP bus system (with CPU 31x-2 DP)
S Execution time of the S7 timer+
S Delay of the inputs and outputs
This corresponds to the sum of the double cycle time and the delay of the inputs
and outputs plus the double bus runtime.
Operating System Processing Time
Table 3-1 contains all the times needed to calculate the operating system
processing times of the CPUs.
The times listed do not take account of
S Test functions, e.g. monitor, modify
S Functions: Load block, delete block, compress block
S Communication
Table 3-1

Operating System Processing Times of the CPUs

Sequence CPU
312 IFM
Cycle control 600 to
1200
ms
Process Image Update
Table 3-2 contains the CPU times for process image updates (Process image
transfer time). The times specified are "ideal values" which are prolonged by
interrupts or by communication of the CPU.
(Process image = PI)
The time required by the CPU time for a process image update is calculated by
K + number of bytes in the PI of module rack "0" A
+ number of bytes in the PI of module racks "1 to 3" B
+ number of bytes in the PI via DP
= Process image transfer time
3-6
CPU CPU CPU
313 314 314 IFM
540 to 540 to 770 to
1040 1040 1340
ms ms ms
D
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
CPU CPU CPU
315 315-2 DP 316-2 DP
390 to 500 to 500 to
820 ms 1030 ms 1030 ms
CPU
318-2
200 ms
A5E00111190-01