Siemens CPU 317-2 PN/DP - Reducing the Response Time with Direct I;O Access

Cycle and reaction times
5.3 Response time
CPU 31xC and CPU 31x, Technical Data
Manual, 01/2006 Edition, A5E00105475-06
5-17
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 5-13)
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 5-15)
Longest response time (Page 5-16)