A media processing device including a platen, a printhead configured to form a nip with the platen, a sensor disposed proximate to the printhead, a detector configured to receive a sensor output from the sensor, and a logic circuit. The sensor is configured to be responsive to demarcation features on a media supply as the media supply is advanced along a feed path past the sensor by the platen. The detector is configured detect edges of the demarcation features, and output a detector output based on the detected edges. The logic circuit is configured to receive the detector output from the detector, determine when to print based on the detector output, and control the printhead and the platen to print on the media unit or printable area.