Siemens SINUMERIK 840Di Function Manual page 255

Dependencies
If the knee-shaped acceleration characteristic curve is parameterized for a machine axis,
then this becomes the default acceleration profile for all traversing operations.
If the effective acceleration profile is changed for a specific axis using the SOFTA or BRISKA
part-program instructions, then an appropriate substitute characteristic curve is used in place
of the knee-shaped acceleration characteristic curve.
It is possible to switch back to the knee-shaped acceleration characteristic curve for a
specific axis by programming DRIVEA.
Acceleration (B2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
2.18 Knee-shaped acceleration characteristic curve
Detailed Description
2-43