Updating Procedure; What Happens During Update? - Siemens SIMATIC S7-400H Manual

6.2.2

Updating Procedure

What happens during update?

On update the execution of the communication functions and of the OBs is
restricted by section. Similarly, all the dynamic data (content of the data blocks,
timers, counters and memory markers) are transferred to the standby CPU.
The update procedure is as follows:
1. All asynchronous SFCs that have recourse to data records of I/O modules
(SFC 13, 51, 55 to 59) are given a "negative" acknowledgement until the end of
the update:
– A current job returns BUSY = TRUE. It will be fully executed after the update
is complete.
– A job interrupted during the update will return the value W#16#80C3
(SFCs 13, 55 to 59) or W#16#8085 (SFC 51) once the update is complete.
With these return values the jobs should be repeated by the user program.
– A job that you want to start during the update will be rejected with the return
value W#16#80C3 (SFCs 13, 55 to 59) or W#16#8085 (SFC 51). With these
return values the jobs should be repeated by the user program once the
update is complete.
2. Notification functions are delayed until the end of the update (see list below).
3. The execution of the OB 1 and of all OBs up to and including priority class 15 is
delayed.
With watchdog interrupts, the generation of new OB requests is inhibited so that
no new watchdog interrupts are stored and, consequently, no new request
errors occur.
Not until the end of the update is a maximum of one request generated and
processed for each watchdog interrupt OB. The time stamp of the watchdog
interrupts that are generated after a delay cannot be evaluated.
4. Transfer of all the data block contents that have been modified the since
link-up.
5. Communication jobs from which the CPU itself derives jobs for other modules
(e.g. I/O) are given a negative acknowledgement (see list below).
6. Initial calls (in other words, calls resulting in manipulation of the work memory,
refer also to System Software for S7-300/400 System and Standard Functions)
of communication functions receive a negative acknowledgement. All the
remaining communication functions are delayed and caught up on once the
update is complete.
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Linking and Synchronizing
6-9