Siemens Sinumerik 840D sl Programming Manual page 577

Read MD and SD values at the preprocessing time
They are addressed from within the synchronized action using the $ characters and evaluated
by the preprocessing time.
ID=2 WHENEVER $AA_IM[z]<$SA_OSCILL_REVERSE_POS2[Z]-6 DO $AA_OVR[X]=0
;Here, reversal range 2, assumed to remain static during operation, is addressed for
oscillation.
Read MD and SD values at the main run time
They are addressed from within the synchronized action using the $ characters and evaluated
by the main run time.
ID=1 WHENEVER $AA_IM[z]<$$SA_OSCILL_REVERSE_POS2[Z]-6 DO $AA_OVR[X]=0
;It is assumed here that the reverse position can be modified by a command during the
machining
Write MD and SD at the main run time
The currently set access authorization level must allow write access. The active states are
listed for all MD and SD in References: /LIS/, Lists (Book 1).
The MD and SD to be written must be addressed preceded by $$.
Example
Program code
ID=1 WHEN $AA_IW[X]>10 DO
$$SN_SW_CAM_PLUS_POS_TAB_1[0]=20
$$SN_SW_CAM_MINUS_POS_TAB_1[0]=30
Job planning
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
10.3 Main run variables for synchronized actions
Comments
; Changing the switching position of software
cams. Note: The switching positions must be
changed two to three interpolation cycles
before they reach their position.
Motion synchronous actions
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