Siemens SINUMERIK 840D sl Function Manual page 487

Permanently assigned PLC axis
The permanently assigned PLC axis is activated via:
MD30460 $MA_BASE_FUNCTION_MASK, bit 5 = 1
During acceleration the axis becomes a neutral axis. A travel request via the NC/PLC
interface converts a neutral axis without a previous axis interchange automatically to a
concurrent positioning axis (PLC axis).
After traversing has been completed, if, for instance, the programmed end position has been
reached, or if traversing has been interrupted, the axis again becomes the neutral axis. In
this state, the axis can be moved or referenced using 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 axis communicates its property as being a permanently-assigned PLC axis to the PLC
via the following NC/PLC interface signal:
DB31, ... DBX71.7 (permanently-assigned PLC axis)
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.
When booting, if it is identified that an axis defined as a geometry axis was simultaneously
defined as permanently assigned PLC axis, then the axis function is signaled with Alarm
4320 "Axis %1 function MA_BASE_FUNCTION_MASK bit 5 and
MC_AXCONF_GEOAX_ASSIGN_TAB not permitted".
If the change to a PLC axis is not possible
For a travel request from the NC/PLC interface area, a change to a PLC axis that is not
possible is acknowledged at the NC/PLC interface using the start signal "Concurrent
positioning axis active".
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, 09/2009, 6FC5397-1BP20-0BA0
K5: Mode groups, channels, axis interchange
6.4 Axis/spindle replacement
487