- Non-Modal Commands: G4, G10L2, G10L20, G28, G30, G28.1, G30.1, G53, G92, G92.1
- Motion Modes: G0, G1, G2, G3, G38.2, G38.3, G38.4, G38.5, G80
- Feed Rate Modes: G93, G94
- Unit Modes: G20, G21
- Distance Modes: G90, G91
- Arc IJK Distance Modes: G91.1
- Plane Select Modes: G17, G18, G19
- Tool Length Offset Modes: G43.1, G49
- Cutter Compensation Modes: G40
- Coordinate System Modes: G54, G55, G56, G57, G58, G59
- Control Modes: G61
- Program Flow: M0, M1, M2, M30*
- Coolant Control: M7*, M8, M9
- Spindle Control: M3, M4, M5
- Valid Non-Command Words: F, I, J, K, L, N, P, R, S, T, X, Y, Z
Reference
https://github.com/xreef/grbl
https://github.com/gnea/grbl-Mega