LinuxCNC M64

M64 is a LinuxCNC G-code M instruction that turns on a specified digital output immediately. The P word selects the output number, with a default range of 0 to 3 and possible expansion through num_dio. It is not synchronized with motion and can break blending.

Source checked5/5 values · 2026-10-26

Specification

1 source

Language	gcode
Code	M64
Group	Digital Output Control
Syntax	M64 P-
Dialect	LinuxCNC

Parameters

Name	Description
P	Specifies the digital output number. The P-word ranges from 0 to a default value of 3; num dio can be used to increase the number of digital I/O when loading the motion controller.

Study notes

M64 is one of four commands in the M62-M65 digital output group; M62/M63 are synchronized with motion and queued, while M64/M65 act immediately.
M64 is not synchronized with movement and will break blending.
M62-M65 will not function unless the appropriate motion.digital-out-nn pins are connected in the HAL file.
The number of digital I/O can be increased with the num_dio parameter when loading the motion controller.