Influences On The Time Behavior; Performance Values For Link-Up And Update - Siemens SIMATIC S7-400H Manual

Link-up and Update
5.3.3

Influences on the Time Behavior

The period during which no I/O updates take place is primarily determined by the
following influencing factors:
number and size of data blocks modified during the update
number of instances of SFBs in the S7 communication information and SFBs
for generating block-related messages
modifications to the System while in Operation
settings via dynamic volume frameworks
expansion of remote I/O (with falling transmission rate and increasing number
of slaves the time required for I/O updates increases.)
In the least favorable cases 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 running up until delay of the interrupts
Deliberate delaying of the update
Delay the update via SFC 90 "H_CTRL" and do not release it again until a state of
lesser communication or interrupt load occurs.
Caution
!
Delaying the update will increase the time during which the fault-tolerant system is
in Solo mode.
5.3.4

Performance Values for Link-up and Update

User program share T
The user program share T
classes > 15 can be calculated using the following formula:
T
P15_AWP
The following table provides the resulting times for some typical values for the
main memory data.
5-26
of the max. blocking time for priority classes > 15
P15_AWP
of the max. blocking time for priority
P15_AWP
in ms = 0.7 size of the DBs in the work memory in Kbyte + 75
S7-400H Programmable Controller Fault-Tolerant Systems
A5E00068197-04