Siemens SIMATIC S7-400H - Figure 12-3 Example of Minimum Signal Duration of an Input Signal During the Update

Link-up and update
12.3 Link-up and update sequence
S7-400H
146 System Manual, 03/2012, A5E00267695-11
Minimum duration of input signals during update
Program execution is stopped for a certain time during the update (the sections below
describe this in greater detail). To ensure that the CPU can reliably detect changes to input
signals during the update, the following condition must be satisfied:
Min. signal duration > 2 x the time required for I/O update (DP and PNIO only)
+ call interval of the priority class
+ program execution time of the priority class
+ update time
+ execution time for programs of higher-priority classes
Example:
Minimum signal duration of an input signal that is evaluated in a priority class > 15 (e.g.
OB 40).
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Figure 12-3 Example of minimum signal duration of an input signal during the update