Siemens SIMATIC S7-400H System Manual page 52

Installation of a CPU 41x–H
5.6 Operating sequence for memory reset
Data retained after a memory reset...
The following values are retained after a memory reset:
● The content of the diagnostics buffer
● The MPI interface parameters. These define the MPI address and the highest MPI address.
● The time
● The status and value of the operating hours counter
Special feature: MPI parameters
The MPI parameters have an exceptional role during CPU memory reset. The table below
lists the MPI parameters which are valid after a memory reset.
Memory reset ...
with inserted FLASH Card
without inserted FLASH Card
Cold start
● A cold start initializes the process image, all memory markers, timers, counters and data
● Program execution resumes with OB 1, or with OB 102 if available.
Restart (warm restart)
● A warn restart resets the process image and the non-retentive memory markers, timers
● Program execution resumes with OB 1, or with OB 101 if available.
● A warm restart after power failure is only possible if memory is backed up.
52
If you had not inserted a flash card during memory reset, the CPU resets the capacity of
the diagnostics buffer to its default setting of 120 entries, i.e. the most recent 120 entries
will be retained in the diagnostics buffer.
You can read the content of the diagnostics buffer using STEP 7.
Note the special features shown in the table below.
blocks with the start values stored in load memory, regardless whether these data were
configured as being retentive or not.
and counters.
Retentive memory markers, timers, counters and all data blocks retain their last valid
value.
MPI parameters ...
... stored on the FLASH Card are valid
... in the CPU are retained and thus valid
System Manual, 09/2007, A5E00267695-03
S7-400H