Siemens SINUMERIK 840Di sl Function Manual page 33

Reading at the time of preprocessing
Unchangeable machine and setting data are addressed from the synchronized action
as in the normal part program commands. They are introduced with
a $-sign.
Example
ID=2 WHENEVER $AA_IM[z]< $SA_OSCILL_REVERSE_POS2[Z]–6 DO
$AA_OVR[X]=0
; Here the reversal range 2 assumed as unchanging during the processing
; is addressed for oscillation
A complete example for oscillation with setting in the reversal range is given in
section 6.2 and:
References:
/FB2/Function Manual, Expanded Functions; Oscillation (P5).
Reading at the time of the main run
Machine data and setting data which change during the processing
are addressed from the synchronized action introduced with $$-sign.
Example
ID=1 WHENEVER $AA_IM[z]< $$SA_OSCILL_REVERSE_POS2[Z]–6 DO
$AA_OVR[X]=0
In this context, it is assumed that the reversal position
can be changed any time during the operation.
Writing at the time of the main run
Requirement:
The currently set access authorization level must allow write access. It is only useful to write
MD and SD from the synchronized action when this takes immediate effect. The
effectiveness for all machine data and setting data is specified in:
References:
/LIS1/ Lists (Book 1), Section "MD-/SD Lists".
Addressing:
Machine and setting data to be written must be addressed preceded by the $$ sign.
Example
ID=1 WHEN $AA_IW[X]>10 DO $$SN_SW_CAM_PLUS_POS_TAB_1[0]=20
$$SN_SW_CAM_MINUS_POS_TAB_1[0]=30
; Changing the switching positions of SW-cams from 20 to 30
Synchronized actions
Function Manual, 11/2006, 6FC5397-5BP10-2BA0
2.3 Special real-time variables for synchronized actions
Detailed description
33