Siemens SINUMERIK 840D sl Function Manual page 829

Effect of activation
The offset for an axis becomes active when the first motion block for this axis is executed
after the offset is activated.
Example of possible chronological sequence:
G0 X100
X150
X200
The "Zero offset external via system frame" is applied immediately.
Channel-specific system frames can be configured through the following machine data:
MD28082 $MC_MM_SYSTEM_FRAME_MASK (System frames SRAM)
Programming
Setting a new offset via the axis-specific system variables:
$AA_ETRANS[axis]=R
The instruction below reads the axisspecific active offset value:
R =$AA_ETRANS[axis]
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Note
The read value can then differ from the previously set value, if the set value has not yet been
activated.
The read value corresponds to a value set previously, if the most recently set value has not
yet been activated. The system frame for the "Zero offset external" exists only if it has been
configured.
DRF offset
The DRF offset enables the adjustment of an additional incremental zero offset for geometry
and additional axes in the basic coordinate system through handwheel.
The DRF offset can be read via the axis-specific system variable:
$AC_DRF[<Axis>]
References:
/FB2/ Function Manual of Extension Functions; Jog with/without Handwheel (H1),
Section: DRF offset
Basic logic functions: Axes, coordinate systems, frames (K2)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
; A new "Zero offset external" is activated by the PLC during this motion.
; The new "Zero offset external" is applied due to G0 programming at the end of the
block (X200), if no velocity reserve is available (100%).
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Detailed description
2.3 Coordinate systems
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