Siemens SIMATIC FM 351 Manual page 37

If your programming device/PC is connected to a CPU, you can now download
the FCs and DBs to the CPU.
The following schematic shows how the FM 351, FCs, DBs and OBs communicate.
Startup
e.g. OB100
FC ABS_INIT
DB_NO
Channel DB
Figure 6-1 Data Exchange between FCs, DBs and the FM 351
FM 351 Positioning Module
C79000-G7076-C351-02
Cyclic operation, parameter
assignment and control
e.g. OB1
FC ABS_CTRL
DB_NO
Channel DB
PARADBNO
Parameter DB
FC ABS_DIAG
DB_NO
Diagnostic DB
Programming the FM 351
FM 351
Jobs
Function switches
Control signals
Return signals
Diagnostic buffer
6-3