Influences On Time-Based Reaction - Siemens SIMATIC S7-400H System Manual

Link-up and update
9.4 Time monitoring
9.4.4

Influences on time-based reaction

The period during which no I/O updates take place is primarily determined by the following
influencing factors:
● the number and size of data blocks modified during the update
● the number of instances of SFBs in S7 communication, and of SFBs for generating
● system modifications in operation
● settings by means of dynamic volume frameworks
● expansion of distributed I/Os (a lower Baud rate and higher number of slaves increases
In the worst case, this period is extended by the following amounts:
● maximum watchdog interrupt cycle used
● duration of all watchdog interrupt OBs
● duration of high-priority interrupt OBs executed until the start of interrupt delays
Explicit delay of the update
Delay the update using SFC 90 "H_CTRL", and re-enable only when the system state shows
less communication or interrupt load.
The update delay increases the time of single mode operation of the fault-tolerant system.
116
block-specific messages
the time required for I/O updates)
CAUTION
System Manual, 09/2007, A5E00267695-03
S7-400H