Siemens Sinumerik 840D sl Programming Manual page 613

Using GET to request an axis from another channel
If, when the GET action is activated, another channel is authorized to write (has the
interpolation right) to the axis ($AA_AXCHANGE_TYP[<axis>] == 2), axis replacement is
used to get the axis from this channel ($AA_AXCHANGE_TYP[<axis>]==6) and assign it to
the requesting channel as soon as possible.
The axis then becomes the neutral axis ($AA_AXCHANGE_TYP[<axis>]==3).
There is no reorganize in the requesting channel.
Assignment as NC program axis with reorganize:
If an attempt to make the axis the neutral axis is already in progress when the GET action is
activated ($AA_AXCHANGE_TYP[<axis>]==6), the axis is requested for the NC program
($AA_AXCHANGE_TYP[<axis>]==5) and assigned to the NC program on the channel as
soon as possible ($AA_AXCHANGE_TYP[<axis>]==0).
Axis already assigned to requested channel
Assignment as NC program axis with reorganize:
If the requested axis has already been assigned to the requesting channel at the point of
activation, and its status is that of a neutral axis (not controlled by the PLC)
($AA_AXCHANGE_TYP[<axis>]==3), it is assigned to the NC program
($AA_AXCHANGE_TYP[<axis>]==0).
Axis in neutral axis status controlled by the PLC
If the axis is in neutral axis status controlled by the PLC ($AA_AXCHANGE_TYP[<axis>]==4),
the axis is requested as a neutral axis ($AA_AXCHANGE_TYP[<axis>] == 8). This locks the
axis for automatic axis replacement between channels in accordance with the value of bit 0 in
MD 10722: AXCHANGE_MASK (bit 0 == 0). This corresponds to
($AA_AXCHANGE_STAT[<axis>] == 1).
Axis is active as neutral command axis/oscillating axis or assigned to PLC
If the axis is active as the command axis/oscillating axis or assigned to the PLC for travel,
PLC axis == concurrent positioning axis, ($AA_AXCHANGE_TYP[<axis>]==1), the axis is
requested as a neutral axis ($AA_AXCHANGE_TYP[<axis>] == 8). This locks the axis for
automatic axis replacement between channels in accordance with the value of bit 0 in MD
10722: AXCHANGE_MASK (bit 0 == 0). This corresponds to
($AA_AXCHANGE_STAT[<axis>] == 1).
A new GET action will request the axis for the NC program ($AA_AXCHANGE_TYP[<axis>]
changes to == 7).
Axis already assigned to NC program
If the axis is already assigned to the NC program ($AA_AXCHANGE_TYP[<axis>]==0) or if
this assignment is requested, e.g., axis replacement triggered by NC program
($AA_AXCHANGE_TYP[<axis>]==5 or $AA_AXCHANGE_TYP[<axis>] == 7), there will be no
change in state.
Job planning
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
Motion synchronous actions
10.4 Actions in synchronized actions
613