Lenze Drive Server Bus server S7 getting started - Manual (Page 24)

Busserver S7
L
85 Busserver S7 DE/EN 1.0
5.2 Typical program flow
The following figure shows the typical sequence of a STEP7 program with OPC access:
DBx OPC
DBx
DBx
FC1
DBx
OB1
DB S7PAR
FC
process data
FB DRIVE
parameter
d 2 rive
FB DRIVE
parameter
drive 1
FB DRIVE
parameter
d n rive
FC
process data
FB DRIVE
parameter
FB DRIVE
parameter
FB DRIVE
parameter
FC
parameter
FC
parameter
• The standard block OB1 forms the basis. This block is included in every STEP7 program and
automatically activated in every cycle. The OB1 calls all other function blocks required for the
particular application.
• In the above figure, the standard block OB1 calls the function FC1 which initiates the real
access to the drives.
• In every cycle, the function FC Process Data is called in FC1 to process the process data.
Since it is not possible to access process data via OPC, you need not change between PLC and
OPC commands in this case.
• The function block FB DRIVE is called several times for OPC access. For each drive, you have to
create an instance with a separate data block.
• Each instance of FB DRIVE has access to two data blocks, DB OPC and DB S7PAR.
• Every time FB DRIVE is called (multiple use), a special instance data block has to be
transmitted, which contains the data for the appropriate drive, e. g. the PROFIBUS address. The
FB DRIVE does not use any global data.
• DB OPC and DB S7PAR must not be changed by the user. The user can, however, write
parameter data jobs from the PLC to the corresponding fields of DB S7PAR using the function
FC Parameter .
• The function FC Parameter can be called at any point in FC1 .
• The change between the parameter data jobs from the OPC and the PLC is made by the FB
DRIVE.
• The function FC Process Data is not affected by this and continues to be called in every cycle.
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