74 Rockwell Automation Publication 2080-UM002G-EN-E - March 2015
Chapter 7 Motion Control
WARNING: During Run Mode Change (RMC), the MC_Power function
block should be disabled, which will power down the axis. Otherwise the
axis will remain powered even if the function block is deleted.
Take note of the following:
• If a new instance of MC_Power accesses the axis, the axis will enter the
error stop state.
• If MC_Power is inside a UDFB and any edit is made to the UDFB that
changes the UDFB template (for example, adding a local variable), the
axis will enter the error stop state.
Movement Function Blocks
Function Block Name Description Correct Axis State for
issuing Function Block
MC_MoveAbsolute This function block commands an axis to a
specified absolute position.
Standstill, Discrete Motion,
Continuous Motion
MC_MoveRelative This function block commands an axis of a
specified distance relative to the actual
position at the time of execution.
Standstill, Discrete Motion,
Continuous Motion
MC_MoveVelocity This function block commands a never
ending axis move at a specified velocity.
Standstill, Discrete Motion,
Continuous Motion
MC_Home This function block commands the axis to
perform the “search home” sequence.
The “Position” input is used to set the
absolute position when reference signal
is detected, and configured Home offset
is reached. This function block completes
at “StandStill” if the homing sequence is
successful.
Standstill
MC_Stop This function block commands an axis
stop and transfers the axis to the state
“Stopping”. It aborts any ongoing function
block execution. While the axis is in state
Stopping, no other function block can
perform any motion on the same axis.
After the axis has reached velocity zero,
the Done output is set to TRUE
immediately. The axis remains in the state
“Stopping” as long as Execute is still
TRUE or velocity zero is not yet reached.
As soon as “Done” is SET and “Execute”
is FALSE the axis goes to state
“StandStill”.
Standstill, Discrete Motion,
Continuous Motion,
Homing
MC_Halt This function block commands an axis to a
controlled motion stop. The axis is moved
to the state “DiscreteMotion”, until the
velocity is zero. With the Done output set,
the state is transferred to “StandStill”.
Standstill, Discrete Motion,
Continuous Motion
ATTENTION: During Run Mode Change, the Movement Function Blocks
can only be deleted when that Function Block has been done or aborted.
Otherwise unintended axis and Function Block behavior may occur.
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