Siemens SINUMERIK 840D sl Function Manual page 473

Permanently assigned PLC axis
The permanently assigned PLC axis is activated by machine data
MD30460 $MA_BASE_FUNCTION_MASK with Bit 5 = 1
During acceleration the axis becomes a neutral axis. When a traverse request is transferred
via the VDI interface, a neutral axis without preceding axis replacement, automatically
changes to a competing positioning axis (PLC axis).
After completing the traverse, if, for instance, the programmed end position has been
reached, or if the traverse has been interrupted, the axis again becomes the neutral axis. In
this condition the axis can be moved or referenced via
JOG with the traverse keys or the handwheel.
Note
A permanently assigned PLC axis cannot be replaced.
The following functions are not possible for a permanently assigned PLC axis:
● Replacement between channels
● Replacement to command axis
● Replacement to Oscillation axis
● Assignment of the axis to the NC program
The permanently assigned PLC axis reports its properties via the VDI interface with
IS DB31, ..., DBX71.7 ("permanently assigned PLC axis") to the PLC.
Axis control
If the axis is not PLC-controlled, it can be controlled by the signals RESET, STOP and
RESUME, which are effective in the channel.
If during acceleration it is detected that an axis which was defined as a geometry axis
simultaneously has been defined as permanently assigned PLC axis, the axis function will be
denied with alarm 4320 axis 1% function MA_BASE_FUNCTION_MASK Bit5 and
MC_AXCONF_GEOAX_ASSIGN_TAB.
If a change to a PLC axis is not possible
In case of a traverse request from the VDI interface area, an illegal change to a PLC axis is
ended with the start signal "Competing Positioning Axis active" at the VDI interface.
Note
Competing positioning axes get their block end points exclusively from the PLC an can be
started at any point in time. Positioning axes are only influenced in their operation at block
ends in the running parts program.
Extended Functions
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Mode Groups, Channels, Axis Replacement (K5)
6.4 Axis/spindle replacement
473