Response To Time-Out; Time Response During Link-Up - Siemens SIMATIC S7-400H Manual

Linking and Synchronizing

Response to time-out

If one of the times monitored exceeds the maximum value configured then the
following process is started:
1. Update aborted
2. Fault-tolerant system remains in single mode with existing master CPU in RUN
mode
3. Reason for aborting entered in the diagnostics buffer
4. OB 72 called (with corresponding start information)
The standby CPU then re-evaluates its system data blocks.
Afterwards – but at least one minute later – there is a new attempt at link-up and
update. If unsuccessful after 10 attempts no further attempts will be made. You
must then initiate link-up and update again.
Reasons for expiration of the monitoring times may include:
• high interrupt load (i.e. of I/O modules)
• high communication load, so that execution of current functions takes longer
• in the final phase of the update large volumes of data have to be copied to the
standby CPU.
6.3.1 Time Response

Time response during link-up

During link-up, the controller in your system should be influenced as little as
possible. Therefore the duration of link-up increases with the rise in the current
loading of your programmable logic controller. Link-up duration depends primarily
on the
• communication load
• scan cycle time
The following applies to non-loaded programmable logic controllers:
Link–up run time = size of the load and working memories in MB × 1 s
+ basic load
The basic load is a few seconds.
When your programmable logic controller is subjected to a high load, the
memory-dependent share can rise to 1 minute per MB.
6-16
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07