MSF — Motion Servo Off

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Description

MSF (Motion Servo Off) disables the drive of an axis and cancels whatever command it was executing. On a stepper axis the Enable pin is released, so the motor is de-energized and no longer holds; on a DC axis the bridge coasts; on a servo axis the status bit clears. Any move or jog in progress is dropped where it is, with no deceleration ramp, and the axis remembers that position. Use MSF when the machine leaves run mode, for a guard-open condition, or to let an operator turn a stepper by hand. Do not use MSF as the normal way to end a move: use MAS for a controlled stop and MSF afterwards.

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Operands

Operand	Type	Format	Valid Range	Required	Description
Axis	Axis	Axis name	Any axis in Explorer ▸ Axes that has a driver	Yes	The axis to disable.

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Scan Behavior

Prescan

Nothing. Every axis starts disabled.

Rung-condition-in is false

Nothing.

Rung-condition-in is true

On this scan and every scan the rung stays true:

• The drive is disabled and DriverOn = 0.
• A move in progress is cancelled: the pending target is dropped, the step train stops at once, and ActualPos stays at the position reached. DN and PC are not set for the cancelled move.
• A jog is stopped. EN and IP clear.
• DN, PC and Error are left as they were.

Postscan

Nothing.

Axis type	What MSF does
Stepper	Releases the Enable pin, drops the pending target. The motor free-wheels; holding torque is gone.
DC	Sets the bridge to 0 duty. The motor coasts, no braking.
Servo	Clears DriverOn. The servo library keeps holding the last angle.

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Axis Members

Motion status lives on the axis, not on a per-instruction tag.

Member	Data type	Set by	Cleared by	Description
DriverOn	BOOL	MSO	MSF	The drive is enabled.
EN	BOOL	MAM, MAJ, MAG while a command is active	Command complete, MAS, MSF	A motion command is engaged.
IP	BOOL	Axis service while steps are being produced	Motion stops, MSF	Motion in process.
DN	BOOL	MAM reaching its target, MSR	Next MAM or MAJ	Instruction done. Not touched by MSF.
PC	BOOL	Same as DN	Same as DN	Process complete.
InMotion	BOOL	Axis service	Axis service	Steps produced this scan.
Dir	BOOL	Axis service	Axis service	1 = forward.
Error	BOOL	Watchdog mismatch, TMC2130 driver fault	MAFR	Axis fault. Not touched by MSF.
ActualPos	REAL	Axis service every scan	—	Position in axis units. Kept across MSF.
CmdPos	REAL	MAM, MAG, MSR	—	Commanded target in axis units.
Counts	DINT	Axis service every scan	MSR, ResetCounts	Raw step counts.
RedefinePos	REAL	MSR	—	Value of the last MSR.
ResetCounts	BOOL	Your logic (write 1)	Firmware, after zeroing	Zero the counts without an MSR.
Watchdog	INT (ms)	Axis properties; your logic may overwrite	—	Mismatch tolerance before Error sets.

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Example

Scenario: The feeder from the MSO page. A second switch, Servo_Off, drops the Feed drive so the operator can move the carriage by hand.

Tags:

• Servo_Off — Servo off, BOOL
• Feed — stepper axis, 80 counts per mm

Rung 1:

—|XIC Servo_Off|———[MSF Feed]———

Scan 1 — Servo_Off = 0. Nothing happens; Feed.DriverOn keeps its value (1 after the MSO page).

Scan 2 — Servo_Off = 1. The drive is released: Feed.DriverOn = 0, Feed.EN = 0. If a move was running, Feed.ActualPos stops where it is.

Values before and after: Feed.DriverOn 1 → 0. A carriage moved by hand while disabled is no longer where ActualPos says; home it with an MSR before the next move.

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See Also

• MSO — Motion Servo On
• MAS — Motion Axis Stop (controlled stop, drive stays on)
• MSR — Motion Set/Redefine Position (re-home after a hand move)
• Motion Instructions — Category index

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Notes

MSF and MSO on the same scan. If both rungs are true, the one scanned last wins. Interlock the two switches or use one selector.

Not a deceleration. A stepper carrying a load and dropped mid-move can overshoot mechanically. For a controlled stop, MAS first, then MSF once IP is 0.

Position is kept, not trusted. ActualPos is not cleared by MSF. It is right only if nothing moved the axis while the drive was off.