Siemens SINUMERIK 840D Function Manual page 213

Only the following signals are an exception:
● NST DB21, ... DBB4 ("feedrate override")
● IS DB21, ... DBX6.2 ("Delete distance to go")
Axisspecific signals
Positioning axes have the following additional signals:
● IS DB31, ... DBX76.5 ("Positioning axis")
● Feedrate for positioning axes/spindles (FA)
● NST DB31, ... DBB0 ("feedrate override") - axis-specific
● IS DB31, ... DBX2.2 ("Distance to go/Spindle reset") Axis-specific deletion of distance to go
Single-axis functions of PLC-controlled axes
The behavior of individual PLC axes can be manipulated in
the following way with machine data:
MD30460 $MA_BASE_FUNCTION_MASK:
● Bit 4 = 1
The axis is exclusively controlled by the PLC.
● Bit 5 = 1
The axis is a permanently assigned PLC axis.
● Bit 6 = 1
The channel-specific NC/PLC interface signal:
DB21, ... DBX6.0 ("feed disable")
is not active for the axis if this is a PLC-controlled axis.
● Bit 7= 1
The channel-specific NC/PLC interface signal:
DB21, ... DBX36.3 ("all axes stationary")
is setindependently of an axis if this is a PLC-controlled axis.
For a PLC-controlled axis:
● The channel-specific NC/PLC interface signal DB21, ... DBX6.0 ("feed disable"), is active if
bit 6 = 0 in machine data MD30460 $MA_BASE_FUNCTION_MASK.
● The channel-specific NC/PLC interface signal DB21, ... DBX36.3 ("all axes stationary") is
only set if bit 7 = 0 in machine data MD30460 $MA_BASE_FUNCTION_MASK.
If an attempt is made to assign an exclusively PLC-controlled axis to the NC program or to
request the axis for the NC program, then this is rejected with Alarm 26075. Alarm 26076 is
generated in the same way for a PLC axis with fixed assignment.
A PLC axis with fixed assignment is a "neutral axis" on power up. For a travel request via the
NC/PLC interface, a concurrent positioning axis automatically changes to a PLC axis without
being interchanged beforehand.
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
P2: Positioning axes
6.7 Control by the PLC
213