Siemens S7 5.5 System datablocks change

Hi all,

I have a question about Siemens Step 7 5.5 system datablocks.

Can the SDB be changed by the PLC itself, or is a change in the SDB always caused by an engineer updating the program, hardware or communication of the PLC?

Comparing SDB's shows that several SDB's changed on a date after my last modifications, but nobody accessed the PLC after that (as far as I know).
According to the S7 manual, purpose of the SDB:

Changes in SDB 702 (type 700), Configuring Connections
SDB 999 (type 999), Configuring Networks/Connections (S7-Routing)
SDB's 1000-1005 (type 3xxx), Configuring Hardware (DP configuration, parameters for CPs and FMs, S7-Routing, Connections)

Would this indicate a change in communication settings after my last modifications?

toont said:

Hi all,

I have a question about Siemens Step 7 5.5 system datablocks.

Can the SDB be changed by the PLC itself, or is a change in the SDB always caused by an engineer updating the program, hardware or communication of the PLC?

Comparing SDB's shows that several SDB's changed on a date after my last modifications, but nobody accessed the PLC after that (as far as I know).
According to the S7 manual, purpose of the SDB:

Changes in SDB 702 (type 700), Configuring Connections
SDB 999 (type 999), Configuring Networks/Connections (S7-Routing)
SDB's 1000-1005 (type 3xxx), Configuring Hardware (DP configuration, parameters for CPs and FMs, S7-Routing, Connections)

Would this indicate a change in communication settings after my last modifications?

Click to expand...

Does the PLC have the correct date set? Could be that simple?
Is the time difference big or small?
What are the actual differences?

To my knowledge SDBs are downloaded as hardware configuration and do not change in runtime.

Kalabdel, thanks for the answer. The time difference between PG and PLC is about half a second.
A comparison of the online and offline HW config exported to a textfile showed the following differences:


Offline HW config_______________________Online HW config

PROFIBUS_TTR "147305"____________________PROFIBUS_TTR "132327"
WATCHDOG "254334"_______________________WATCHDOG "209400"
TTR_SLAVE_INT "48512"___________________TTR_SLAVE_INT "47198"
DDB_TIME_PCI "51"_______________________DDB_TIME_PCI "42"
TIME_SHORTCUT_OUTOF_RING "51"___________TIME_SHORTCUT_OUTOF_RING "42"
TIME_SHORTCUT_OUTOF_RING_V5SP3 "403"____ TIME_SHORTCUT_OUTOF_RING_V5SP3 "362"
TIME_SHORTCUT_IN_RING "51"______________TIME_SHORTCUT_IN_RING "42"
TIME_SHORTCUT_IN_RING_V5SP3 "30"________TIME_SHORTCUT_IN_RING_V5SP3 "27"
DCI_COUNTER "16"________________________DCI_COUNTER "14"
SLAVE_ACTIVE_PASSIVE "0"________________SLAVE_ACTIVE_PASSIVE "1"