MSR — Motion Set/Redefine Position

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Description

MSR (Motion Set/Redefine Position) tells an axis where it is. On the false-to-true transition of its rung the axis position is set to the Position operand without any motion: ActualPos, CmdPos and Counts take the new value, RedefinePos records it, and DN and PC set. Any move in progress is cancelled. Use MSR at a home sensor to establish the machine zero, to re-home after a hand move, or to zero the counter at power-up. Do not use MSR to move an axis; nothing turns. Use MAM for that.

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Operands

Operand	Type	Format	Valid Range	Required	Description
Axis	Axis	Axis name	Any stepper or servo axis with a driver	Yes	The axis to redefine.
Position	REAL	Literal or tag	Any value in axis units	Yes	The value the current position becomes. A tag is read on the edge.

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Scan Behavior

Prescan

Nothing. The edge memory starts false, so a rung already true on the first scan redefines on that scan.

Rung-condition-in is false

Nothing. The edge memory is armed.

Rung-condition-in is true

On the rising edge only: the axis’s current position and its target are both set to Position, so no move results; Counts = Position × counts per unit; ActualPos = CmdPos = RedefinePos = Position; DN = PC = 1. A move that was running stops where it is. Further true scans do nothing.

Postscan

Nothing.

Before	After the edge
ActualPos = 174 (wherever the axis was)	ActualPos = Position
Counts = 13920	Counts = Position × counts per unit
DN = 0	DN = 1, PC = 1
Move in progress	Cancelled, axis at rest

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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
RedefinePos	REAL	MSR	—	Value of the last MSR. This member exists for MSR.
ActualPos	REAL	MSR, axis service every scan	—	Position in axis units.
CmdPos	REAL	MSR, MAM, MAG	—	Commanded target in axis units.
Counts	DINT	MSR, axis service every scan	ResetCounts	Raw step counts.
DN	BOOL	MSR, MAM reaching its target	Next MAM or MAJ	Instruction done.
PC	BOOL	Same as DN	Same as DN	Process complete.
EN	BOOL	MAM, MAJ, MAG while a command is active	Command complete, MAS, MSF	A motion command is engaged. Not set by MSR.
IP	BOOL	Axis service while steps are being produced	Motion stops	Motion in process.
InMotion	BOOL	Axis service	Axis service	Steps produced this scan.
Dir	BOOL	Axis service	Axis service	1 = forward.
DriverOn	BOOL	MSO	MSF	The drive is enabled. MSR works with the drive on or off.
Error	BOOL	Watchdog mismatch, TMC2130 driver fault	MAFR	Axis fault.
ResetCounts	BOOL	Your logic (write 1)	Firmware, after zeroing	Zero the counts without an MSR; the same as MSR 0.
Watchdog	INT (ms)	Axis properties; your logic may overwrite	—	Mismatch tolerance before Error sets.

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Example

Scenario: A set-home pushbutton declares the Feed carriage’s current position to be 0 mm, after the operator has jogged it against the reference stop.

Tags:

• Set_Home — Set home position, BOOL
• Feed — stepper axis, 80 counts per mm

Rung 1:

—|XIC Set_Home|———[MSR Feed  Redefine 0]———

Scan 1 — Set_Home = 0. The carriage sits at 174 mm after the jog on the MAJ page: Feed.ActualPos = 174.

Scan 2 — Set_Home = 1 (rising edge). Nothing moves. Feed.ActualPos = 0, Feed.Counts = 0, Feed.RedefinePos = 0, Feed.DN = 1.

Values before and after: Feed.ActualPos 174 → 0 with the motor standing still. Every absolute MAM from now on is measured from this spot.

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See Also

• MAM — Motion Axis Move (absolute moves need a home)
• MAJ — Motion Axis Jog (find the home sensor)
• MSF — Motion Servo Off (re-home after a hand move)
• Motion Instructions — Category index

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Notes

Homing pattern. XIC Home_Sw → MSR Feed 0 on its own rung, with the jog toward the switch on another. The MSR fires on the scan the switch closes and cancels the jog’s pending target; release the jog button and the axis is homed.

ResetCounts is the short form. Writing 1 to <axis>.ResetCounts from an OTE zeroes the counts on the next scan and the bit clears itself. MSR does the same for any value and records it in RedefinePos.

Not a move. Redefining to 100 when the axis is at 0 does not send it anywhere. A following absolute MAM to 100 would then do nothing.

Geared followers. MSR on a master axis changes the master’s position, so a follower geared to it drives to the new master × Ratio.

Servo axis. MSR sets the reported angle without moving the horn; the physical servo stays where the last MAM put it.