MAM — Motion Axis Move

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Description

MAM (Motion Axis Move) moves an axis to a position. On the false-to-true transition of its rung it takes the Position, Speed and Accel operands and starts a trapezoidal move; the axis service then runs the move to completion over the following scans whether or not the rung stays true. EN and IP are 1 while the move runs; DN and PC set when the target is reached. An absolute move goes to Position; an incremental move goes Position units from where the axis is. Use MAM for every point-to-point positioning task. Do not use MAM on a DC axis, which has no position, and do not hold its rung expecting the move to repeat; MAM acts once per rising edge.

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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 move.
Position	REAL	Literal or tag	Any value in axis units; servo axis: 0 to 180 degrees	Yes	Target (absolute) or distance (incremental). A tag is read on the edge.
Move Type	Choice	absolute or incremental	—	Yes	Absolute: go to Position. Incremental: go Position units from the current position, sign giving direction.
Speed	REAL	Literal or tag	> 0, axis units per second	Yes	Maximum speed of the move.
Accel	REAL	Literal or tag	> 0, axis units per second squared	Yes	Acceleration and deceleration of the move.

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Scan Behavior

Prescan

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

Rung-condition-in is false

Nothing new is commanded. A move already started continues to its target. The edge memory is armed for the next true scan.

Rung-condition-in is true

On the first true scan after a false one (the rising edge): the operands are read, the axis speed and acceleration are set, the target is loaded, CmdPos = target, EN = 1, DN = PC = 0. On following true scans nothing more is commanded; the axis service keeps stepping toward the target and sets IP and InMotion while it does. When the target is reached, DN = PC = 1 and EN = IP = 0.

A new rising edge while a move is running retargets the axis at once, with the new speed and acceleration.

Postscan

Nothing.

Scan	EN	IP	DN	PC	ActualPos
Before the edge	0	0	last	last	at rest
Edge scan	1	1	0	0	starts toward target
Moving	1	1	0	0	approaching target
Target reached	0	0	1	1	= target

Servo axis. The angle is written immediately on the edge and DN/PC set on the same scan; Speed and Accel are ignored because a hobby servo ramps on its own.

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Axis Members

Motion status lives on the axis, not on a per-instruction tag. Every member is a reference you can use anywhere (XIC Feed.DN, GRT Feed.ActualPos 100).

Member	Data type	Set by	Cleared by	Description
EN	BOOL	MAM edge, MAJ, MAG	Target reached, MAS, MSF	A motion command is engaged.
IP	BOOL	Axis service while steps are being produced	Motion stops	Motion in process.
DN	BOOL	Target reached, MSR	MAM edge, MAJ start	Instruction done.
PC	BOOL	Same as DN	Same as DN	Process complete. Same timing as DN in this release.
CmdPos	REAL	MAM edge (the target, absolute), MAG, MSR	—	Commanded target in axis units.
ActualPos	REAL	Axis service every scan	—	Position in axis units.
Counts	DINT	Axis service every scan	MSR, ResetCounts	Raw step counts.
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.
Error	BOOL	Watchdog mismatch, TMC2130 driver fault	MAFR	Axis fault.
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: A move pushbutton sends the Feed carriage to 150 mm at 50 mm/s, accelerating at 200 mm/s². The drive was enabled on the MSO page.

Tags:

• Move_Cmd — Move command, BOOL
• Feed — stepper axis, step/dir on D8/D9, linear, 80 counts per mm

Rung 1:

—|XIC Move_Cmd|———[MAM Feed  Pos 150  ABS  Speed 50  Accel 200]———

Scan 1 — Move_Cmd = 0. At rest at 0 mm: Feed.ActualPos = 0, Feed.EN = 0, Feed.DN = 0.

Scan 2 — Move_Cmd = 1 (rising edge). The move starts: Feed.CmdPos = 150, Feed.EN = 1, Feed.IP = 1. The block paints neutral; the wire shows the rung is true.

About three seconds later. Feed.ActualPos = 150, Feed.DN = 1, Feed.PC = 1, Feed.EN = 0, Feed.IP = 0. Watch it in the Tag Browser: expand Feed while the simulator runs and ActualPos climbs to 150.

Values before and after: Feed.ActualPos 0 → 150; Feed.DN 0 → 1. Holding Move_Cmd does nothing further. Release it and press again to repeat the move (which, being absolute, goes nowhere the second time).

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See Also

• MAS — Motion Axis Stop (abort a move)
• MAJ — Motion Axis Jog
• MSR — Motion Set/Redefine Position (home before absolute moves)
• MAG — Motion Axis Gear
• MSO — Motion Servo On (enable the drive first)
• Adding an Axis — units, counts per unit and driver pins
• Motion Instructions — Category index

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Notes

Home first. Absolute positions are measured from wherever the counter was zero. Use an MSR at a home sensor, or ResetCounts, before the first absolute move after power-up.

Interlock with the drive. A move commanded while DriverOn is 0 is counted but not performed: ActualPos reaches the target while the motor never turned. Condition every MAM on XIC <axis>.DriverOn.

Units. Position is in the axis unit named in the axis properties (mm, deg, rev); Speed in units per second; Accel in units per second squared. The conversion to steps uses the axis’s Counts per unit.

Speeds a small controller can produce. An Uno steps at a few thousand pulses per second at most. Speed × counts per unit is the step rate you are asking for; a rate the controller cannot keep up with is simply slower, not faulted.

Incremental sign. A negative Position in an incremental move goes backwards. CmdPos shows the resulting absolute target.

Servo axis. Position is the servo angle in degrees, clamped by the servo library to its travel.