Siemens SINUMERIK 840D sl Programming Manual page 160

Flexible NC programming
1.24 Subprogram technique
NOTICE
Call-by-reference parameter transfer
Parameters transferred using call-by-reference must not be left out of the subprogram call.
NOTICE
AXIS data type
AXIS data type parameters must not be left out of the subprogram call.
Checking the transfer parameters
System variable $P_SUBPAR [ n ] where n = 1, 2, etc., can be used to check whether a
parameter has been transferred explicitly or left out in the subprogram. The index n refers to
the sequence of the formal parameters. Index n = 1 refers to the first formal parameter, index
n = 2 to the second formal parameter, and so on.
The following program excerpt shows an example of how a check can be performed based
on the first formal parameter:
Programming
PROC SUB_PROG (REAL X, REAL Y, REAL Z)
N20 IF $P_SUBPAR[1]==TRUE
...
N40 ELSE
...
N60 ENDIF
...
N100 RET
160
Comment
; Formal parameters: X, Y, and Z
; Check of the first formal parameter X.
; These actions are taken if the formal
parameter X has been transferred
explicitly.
; These actions are taken if the formal
parameter X has not been transferred.
; General actions
Programming Manual, 03/2013, 6FC5398-2BP40-3BA1
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