Siemens SIMATIC S7-400H Manual page 128

Linking and Synchronizing
Table 6-3
The following assumptions were made for this formula:
• 80% of the data blocks are modified prior to delaying the interrupts of priority
classes > 15.
This value must be determined more accurately for fail-safe systems in
particular in order to avoid a time-out of the driver blocks (see Section 6.3.2).
• Approximately 100 ms of update time are allowed for each megabyte of working
memory assigned by data blocks for currently running or held-back
communication functions.
Depending on the communication load of your programmable logic controller,
you have to add to or deduct from the setting of T
6-26
Typical values for the user program share T
max. blocking time for priority classes > 15
Main memory data
5 Mbyte
10 Mbyte
of the
P15_AWP
T
P15_AWP
3.66 s
7.24 s
.
P15_AWP
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07