Siemens SINUMERIK 840Di Function Manual page 357

Deselection
The NC detects that the function has been deselected on the basis of command FXS[x]=0
and specifies a speed or torque setpoint of "0", i.e. zero clamping torque.
The NC then resets IS "Activate travel to fixed stop"
(DB31, ... DBX62.4) and "Fixed stop reached" (DB31, ... DBX62.5).
If torque-controlled operation is activated, the PLC must first select the unassigned gear
stage in which the torque limitation is effective and switch the drive over to speed-controlled
operation (a speed setpoint of "0" is applied by NC). The PLC must also deactivate the
speed controller monitoring function.
The PLC then activates the preceding gear stage, thus deactivating the torque limitation. It
also switches on the speed control monitoring function again.
Depending on the machine parameter:
MD37060 FIXED_STOP_ACKN_MASK
the NC waits for the PLC to acknowledge by resetting IS
"Activate travel to fixed stop" (DB31, ... DBX3.1) and/or
"Acknowledge fixed stop reached" (DB31, ... DBX1.1).
The C-axis then switches over to position control mode (follow-up mode is terminated) and
synchronization with the new actual position takes place.
The programmed travel motion is then executed.
A block change is executed after the target position has been reached.
Travel to Fixed Stop (F1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Detailed Description
2.3 Travel to fixed stop with analog drives
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