Linking and Synchronizing
6-27
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
6.4 Peculiarities during Link-up and Update
Requirement of input signals during the update
During the update the process signals read in previously are retained and are not
updated. Modification of a process signal during the update will only be recognized
by the CPU if the modified signal state remains at the end of the update.
Pulses (signal change “0 → 1 → 0” or “1 → 0 → 1”) occurring during the update will
not be recognized by the CPU.
Make sure, therefore, that the time between two signal changes (pulse duration) is
always greater than the time required for the update.
Communication links and functions
In contrast to earlier firmware versions, links to the master CPU are no longer
broken. However, associated communication jobs are not executed during the
update. They are stored and caught up on when one of the following cases occurs:
• the update is complete and the system is in Redundant mode
• the update and master/standby switch-over are complete, the system is in
single mode
• the update was aborted (e.g. due to a time-out) and the system is back in single
mode.
It is not possible for the communication blocks to make an initial call during the
update.
Reset instruction on aborting link-up
If the link-up is aborted whilst the contents of the load memory are being copied from
the master CPU to the standby CPU then the standby CPU will given a Reset
instruction. This is signaled by an entry in the diagnostics buffer with the event ID
W#16#6523.
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