What M112 means
Marlin describes M112 as a full shutdown and notes that a reset is required. Without its emergency parser, a serial M112 can wait behind queued commands. RepRapFirmware terminates moves and disables motors and heaters but can leave the power supply on. Klipper documents M112 as Emergency stop.
A software command depends on a powered, responsive controller and a communication path that delivers it. Firmware documentation therefore warns against treating it as a substitute for a hardwired emergency-stop circuit or a device that removes hazardous power.
Syntax and parameters
M112No parametersRequests the target firmware's emergency shutdown behavior.
Practical examples
Software shutdown request
M112 ; firmware emergency shutdown requestThe comment states intent; actual response, latency and reset behavior come from the connected firmware and hardware.
Keep the safety boundary explicit
M112 ; software stop is not a power disconnectThe second comment documents that a software command is not evidence that hazardous power has been removed.
Firmware context
| System | Status | What changes |
|---|---|---|
| Marlin | Common | Stops the machine and requires reset; queue latency depends on the emergency parser and transport path. |
| Klipper | Common | Documented as Emergency stop and places the printer in a shutdown state. |
| RepRapFirmware | Common | Terminates moves and shuts down motors and heaters; the PSU may remain powered and reset or power-cycle is required. |
| CNC controllers | Check dialect | Emergency-stop architecture is controller- and machine-specific; M112 is not a portable CNC safety command. |
What this viewer can show
The viewer never executes M112. It continues parsing later file lines for inspection and does not claim that a printer would execute them, stop safely or remove power.
Common mistakes
- Software E-stop is not a substitute for a safety-rated hardwired stop.
- Serial buffering can affect how quickly a command reaches firmware.
- A file containing M112 is not proof that the target printer or host will handle it as expected.
Primary sources
This page is an original explanation, reviewed against the firmware documentation below. Always confirm commands against the firmware and configuration on the machine that will execute them.