Citizen iDP-3550 User Manual page 111

ESC "U" n
[Function] Specifying/Canceling the Unidirectional print mode
[Code] <1B>H <55>H n
[Range] 0 n 255
[Outline] This command selects/deselects unidirectional print. n is valid only for the least significant
bit.
[Caution] If unidirectional print is selected, the printer will print from the left to the right. When you
want to prevent horizontal shear in printing at high accuracy, specify unidirectional print with
this command. (For double height print, etc.)
n Function
0 Deselects
1 Selects