Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 100)

Cycle and reaction times
5.3 Response time
CPU 31xC and CPU 31x, Technical data
5-18
Manual, Edition 08/2004, A5E00105475-05
Calculation
The (longest) response time is the sum of:
Table 5-11 Formula: Longest response time
2 x process image transfer time for the inputs
+ 2 x process image transfer time for the outputs
+ 2 x program processing time
+ 2 × operating system processing time
+ 2 x program processing time
+ 4 x PROFINET IO update time (only if PROFINET IO is used.)
+ 4 x DP cycle time on PROFIBUS DP (only if PROFIBUS DP is used.)
+ I/O delay
= Longest response time
Equivalent to the sum of 2 x the cycle time + I/O delay time + 4 x times the PROFINET IO
update time or 4 x times the DP cycle time on PROFIBUS DP.
See also
Overview (Page 5-14)
5.3.4 Reducing the response time with direct I/O access
Reducing the response time
You can reach faster response times with direct access to the I/O in your user program, e.g.
with
•
L PIB or
• T PQW
you can partially avoid the response times described above.
Note
You can also achieve fast response times by using process interrupts.
See also
Shortest response time (Page 5-16)
Longest response time (Page 5-17)