Siemens Sinumerik 840D sl Programming Manual page 294

Coordinate transformation (FRAMES)
5.1 Coordinate transformation via frame variables
$P_ACTFRAME
Current, resulting complete frame that results from chaining
• the current basic frame variable $P_BFRAME,
• the currently settable frame variable $P_IFRAME with system frames and
• the currently programmable frame variable $P_IFRAME with system frames.
System frames, see Section "Frames that Act in the Channel"
$P_ACTFRAME describes the currently valid workpiece zero.
If $P_IFRAME, $P_BFRAME or $P_PFRAME are changed, $P_ACTFRAME is recalculated.
$P_ACTFRAME corresponds to $P_BFRAME:$P_IFRAME:$P_PFRAME
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Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
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