Dymo LabelWriter 450 Duo Label Printer User Manual download pdf (Page 9)

additional <syn>, <etb>, or <esc> characters will be treated as print line data, representing

pixels to print, until the required number of bytes for the print line are received.

The character received by the printer after the last data character should be an <esc> character,

denoting a command sequence, or a <syn> or <etb> character, denoting another line of raster

data. Any other characters are ignored.

To reset the printer after a synchronization error or to recover from an unknown state, the host

computer needs to send at least 85 continuous <esc> characters to the printer. This 85-character

sequence is required in case the printer is in a mode in which it expects a raster line of data. The

85 <esc> characters exceed the default number of bytes required for a full line of raster data

(84); this ensures that the printer looks for an ESC command.

Note: A minimum of 85 <esc> characters are required, as this is one more than the longest

possible string of data bytes that the printer could encounter.

Label Positioning

A motor-driven platen, which acts as a pinch roller, controls label movement within the printer.

The control electronics track the logical position on a label by counting motor steps. An infrared

LED photocell detects the top-of-form sense hole that is located between labels. The sense hole

re-syncs the logical counter to a known value that corresponds to the number of motor steps

between the sensor and the cutter bar. Top-of-form position (the inter-label gap over the cutter

bar) is reached when the logical counter decrements to zero.

Top-of-Form Sync

At power up, label position is always assumed to be correct due to the self re-syncing described

above. If an Out of Paper condition is detected at power up, an Advance to Top-of-Form

command is issued and the stepper motor will advance until either a top-of-form sense hole is

detected, causing a re-sync, or until the counter has advanced the equivalent of one full label.

This Load Paper condition also causes the stepper motor to step at a slower rate to help

overcome the frictional drag caused by the print head rubbing directly on the rubber platen.

Label Length

At power up, the label length variable is set to a default value of 3058 (in 300ths of an inch

units), which corresponds to approximately 10.2 inches. The Set Label Length command

sequence (<esc> L nl n2) allows the host software to change the label length variable to

accommodate longer lengths. If longer length labels are used, it is the responsibility of the host

computer to load (and/or re-load) the required label length variable every time the printer is

reset by a power-on reset or a software reset.

When the label length variable is set to any negative 2 byte integer value (0x8000-0xFFFF), it

allows for the use of continuous form paper. In the continuous form mode, the Form Feed

command (<esc> E) is changed to feed enough dot lines to allow for the last line of print data to

extend past the printer tear-bar.

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Dymo LabelWriter 450 Duo Label Printer User Manual Page 9