Siemens SINUMERIK 840Di Function Manual page 962

Detailed description
2.7 Structure and functions of the basic program
2.7.6 Functions of the basic program called from the user program
General
In addition to the modules of the basic program, which are called at the start of OBs 1, 40
and 100, functions are also provided, which can be called at a suitable point in the user
program and supplied with parameters.
These functions can be used, for example, to pass the following jobs from the PLC to the
NCK:
• Traverse concurrent axes (FC 15, FC 16),
• Start asynchronous subprograms (ASUBs) (FC 9),
• Select NC programs and NC blocks (FB 4),
• Control of spindle (FC 18),
• Read/write variables (FB 2, FB 3).
Concurrent axes
The distinguishing features of concurrent axes are as follows:
• They can be traversed either from the PLC or from the NC.
• They can be started from a function call on the PLC in all operating modes.
• The start is independent of NC block boundaries.
Function calls are available for positioning (FC 15) and indexing axes (FC 16).
2-50
Note
The following note will later help you to check and diagnose a function call (FCs, FBs of
basic program). These are FCs and FBs, which are controlled by a trigger signal (e.g., via
parameter Req, Start, etc.), and which supply an execution acknowledgment as an output
parameter (e.g., via parameter Done, NDR, Error, etc.). A variable compiled of other
signals, which produce the trigger for the function call should be set. Start conditions may
be reset only as a function of the states of parameters Done, NDR and Error.
This control mechanism may be positioned in front of or behind the function call. If the
mechanism is placed after the call, the output variables can be defined as local variables
(advantage: Reduction of global variables, flags, data variables and timerelated
advantages over data variables).
The trigger parameter must be a global variable (e.g., flag, data variable).
In OB 100, jobs still activated by the user program (Parameter Req,
Start, etc.:= TRUE) must be set to zero at the named parameters. A POWER OFF/ON
could result in a state in which jobs are still active.
Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0