Citizen iDP-3550 User Manual page 92

ESC "U" n
[Function] Selecting the Unidirectional/Bidirectional print mode
[Code] <1B>H <55>H n
[Range] 0 n 255
[Outline] This command selects or deselects unidirectional print.
ESC "@"
[Function] Initializing the printer
[Code] <1B>H <40>H
[Outline] This command cancels various conditions set after power-on to initializes the printer to the
conditions having existed at power-on. However, the input buffer is not initialized.
n0 = 0 Bidirectional print
n0 = 1 Unidirectional print