LinuxCNC M63 Digital Output Off, Synchronized

M63 turns a digital output off, with the change queued to occur in step with machine motion. The P word selects the output number, which ranges from 0 to a default maximum of 3. The queued change is applied at the start of the next motion command, so a motion G-code should follow the M63.

Source checked5/5 values · 2026-10-26

Specification

1 source

Language	gcode
Code	M63
Group	digital output control
Syntax	M63 P-
Dialect	LinuxCNC

Parameters

Name	Description
P-	Digital output number, ranging from 0 to a default value of 3; adjustable using the num dio parameter when loading the motion controller.

Study notes

M63 belongs to the M62-M65 digital output control group; M62 turns an output on synchronized with motion, and M64/M65 turn an output on/off immediately.
The P word specifies the digital output number and ranges from 0 to a default value of 3; the count can be increased with the num_dio parameter when loading the motion controller.
M62 and M63 commands are queued; a later command referring to the same output number overwrites the earlier setting, and multiple output changes can be programmed with more than one M62/M63 line.
The output change occurs at the beginning of the next motion command; if no motion command follows, the queued change does not happen, so a motion G-code (G0, G1, etc.) should be programmed right after M62/M63.
M63 will not function unless the corresponding motion.digital-out-nn HAL pins are connected to outputs in the HAL file.
M64 and M65 take effect immediately as received by the motion controller, are not synchronized with movement, and will break blending.