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Parameters

• Snnn minimum target temperature, waits until within 2.5C of target if heating
• Rnnn accurate target temperature, waits until within 2.5C of target always
• Tn optional tool number

Example

• M109 S215

Deprecated in RRF, but widely generated by slicers. To get the same behaviour, use G10/M568 followed by M116

To better support slicers that don't select a tool when doing a single-extrusion print, RRF will always select a tool when processing M109. If the T parameter is present, that tool will be selected. If no T parameter is present and no tool is already selected, the tool with the lowest non-negative tool number will be selected (typically tool 0).

Note: M109 will not wait for temperatures below 40c because in many cases they may never be reached due to ambient temps. So if you want to wait for a hotend to cool, use 41c or higher.