Fujitsu C145-C037-01EN Product Description page 65

(2) DTR protocol
The DTR signal is set off (low). That is, the Busy signal is issued when 255 bytes of data remain in the buffer.
When the printer is placed offline, the DTR signal is set off (low).
Transmission must stop within 255 bytes after the DTR signal is set off (low).
The validity of data cannot be guaranteed if data exceeding the buffer capacity is transmitted regardless of the
DTR signal.
Buffer-full recovery timing:
Data transmission is suspended while the DTR signal is set off (low), but printing continues. When the buffer
empty area exceeds 255 bytes, the DTR signal is set on (high) indicating that the printer is ready to accept data.
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