Siemens SINUMERIK 840Di Function Manual page 1197

I/O expansion
I/O modules, central
PROFIBUS DP interfaces
Interfaces (MPI)
Note
Number of PROFIBUS slaves
The content of SDB 2000 and other associated SDBs is stored by the PLC operating system
in internal data structures which can also be accessed by the PROFIBUS ASIC.
Furthermore, information from SDB 2000 is also conditioned (CPI interface) and transmitted
to the NCK and the PLC basic program. This is necessary in order to control drives and
PROFIsafe modules on the PROFIBUS. A memory area defined by the PLC is available for
these data structures. Its size is limited by the maximum number of slots. This means that
during loading, SDBs with fewer slaves than listed above may be refused. A slot is usually a
slave module or the slave itself. Only on a module with both I and Q areas does one module
count as 2 slots. It is, therefore, not possible to specify the size of SDB 2000 exactly. It
cannot be determined whether the configuration is legal until the SDB container has been
loaded to the CPU. The values shown above must be taken as guide values only. If the
configuration is illegal, a general reset request is issued when the SDBs are loaded. The
cause of the configuring error can be found in the diagnostic buffer on completion of the
general reset.
PLC Basic Program Solution Line (P3 sl)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
2.1 Key PLC CPU data for 810D, 840D and 840Di
PROFIBUS only
1 (2)
1 (0)
Detailed Description
24 (option)
1 (2)
1 (0)
2-3