MAJ — Motion Axis Jog

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Description

MAJ (Motion Axis Jog) runs an axis at a constant speed in one direction for as long as its rung is true, and stops it the moment the rung goes false. It is the hold-to-run instruction: put it behind a jog pushbutton. On a stepper axis the speed is in axis units per second; on a DC axis it is a percentage of full speed. There is no target and no DN; EN and IP are 1 while the jog runs. Use MAJ for manual positioning, for finding a home sensor, and for continuous feeds. Do not use MAJ for a move to a known position; that is MAM. Do not use it on a servo axis, which cannot jog.

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Operands

Operand	Type	Format	Valid Range	Required	Description
Axis	Axis	Axis name	Any stepper or DC axis with a driver	Yes	The axis to jog.
Speed	REAL	Literal or tag	Stepper: > 0, axis units per second. DC: 0 to 100, percent of full duty	Yes	Jog speed. A tag lets the speed change while jogging.
Direction	Choice	fwd or rev	—	Yes	fwd counts up, rev counts down.
Accel	REAL	Literal or tag	> 0	No	Accepted by the dialog but not applied to a jog in this release: a jog starts and stops at Speed with no ramp. Keep Speed modest on a loaded axis.

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Scan Behavior

Prescan

Nothing.

Rung-condition-in is false

If a jog was running it stops at once. EN and IP clear. DN and PC stay 0. If no jog was running, nothing.

Rung-condition-in is true

Every scan the rung is true the jog command is re-issued: speed and direction are taken from the operands, EN = 1, and DN and PC are cleared. The axis service steps the motor at that speed and sets IP and InMotion. ActualPos and Counts follow the motion.

Postscan

Nothing.

Condition	EN	IP	DN / PC	Axis
Rung false	0	0	Unchanged	Stopped
Rung true, drive on	1	1	0	Runs at Speed in Direction
Rung true, drive off	1	1	0	Counter runs, motor does not turn (see Notes)

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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
EN	BOOL	MAJ while its rung is true, MAM, MAG	Rung false, MAS, MSF	A motion command is engaged.
IP	BOOL	Axis service while steps are being produced	Motion stops	Motion in process.
DN	BOOL	MAM reaching its target, MSR	MAJ start, next MAM	Instruction done. A jog never sets it.
PC	BOOL	Same as DN	Same as DN	Process complete.
Dir	BOOL	Axis service	Axis service	1 = forward: follows Direction.
InMotion	BOOL	Axis service	Axis service	Steps produced this scan.
DriverOn	BOOL	MSO	MSF	The drive is enabled.
Error	BOOL	Watchdog mismatch, TMC2130 driver fault	MAFR	Axis fault.
ActualPos	REAL	Axis service every scan	—	Position in axis units; changes at Speed while jogging.
CmdPos	REAL	MAM, MAG, MSR	—	Not written by MAJ.
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: A jog-forward pushbutton advances the Feed carriage at 20 mm/s while held.

Tags:

• Jog_Fwd — Jog forward, BOOL
• Feed — stepper axis, 80 counts per mm, drive enabled by MSO

Rung 1:

—|XIC Jog_Fwd|———[MAJ Feed  Speed 20  Dir fwd]———

Scan 1 — Jog_Fwd = 0. The axis is at rest; Feed.IP = 0.

Scan 2 — Jog_Fwd = 1. The axis runs forward at 20 mm/s: Feed.EN = 1, Feed.IP = 1, Feed.Dir = 1, Feed.ActualPos rising 20 per second.

Values before and after: held for one second from 150 mm, Feed.ActualPos reads about 170 when the button is released, and the axis holds there.

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See Also

• MAS — Motion Axis Stop
• MAM — Motion Axis Move (move to a position)
• MSO — Motion Servo On (enable the drive first)
• Motion Instructions — Category index

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Notes

Interlock with the drive. A jog commanded while DriverOn is 0 still counts steps; the motor does not turn and ActualPos drifts from reality. Use XIC Jog_Fwd → XIC Feed.DriverOn → MAJ Feed.

Two jogs, one axis. Forward and reverse jog rungs are normal. If both are true the later rung wins on each scan; interlock the buttons.

MAS does not end a held jog. MAJ re-issues its command every scan, so a stop instruction only interrupts it for a scan. The jog ends when its rung goes false.

DC axis. Speed is 0 to 100 percent duty; direction reverses the bridge. When the rung drops the duty goes to 0 and the motor coasts.

Servo axis. A servo cannot jog. MAJ on a servo axis moves nothing; use MAM to set an angle.

Watchdog. A jog whose motor is stalled still counts steps, so the watchdog does not see a mismatch on a plain step/dir driver. Only a TMC2130 reports a stalled or shorted driver.