Lenze Drive Server Bus server S7 getting started Bedienungsanleitung PDF herunterladen (Seite 24)

Busserv er S7

85Busserver 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

FC1

DBx

OB1

DB S7PAR

process data

FB DRIVE

parameter

d2rive

FB DRIVE

parameter

drive 1

FB DRIVE

parameter

dnrive

process data

FB DRIVE

parameter

FB DRIVE

parameter

FB DRIVE

parameter

• The standard block OB1 forms the basis. This bl ock 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 a ccess 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 separa te data block.

• Each instance of FB DRIVE has access to two data blocks, DB OPC and DB S7P AR.

• 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 S7P AR 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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