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The LaserWriter Select 360 parallel port is unidirectional, however the
LaserWriter driver 8.x expects to receive information back from the
printer. The driver relies on bidirectional communications because it
sends out various queries to obtain information about the characteristics
of the target output device (such as features, fonts, etc.) before
beginning a print job. The 7.x LaserWriter driver does not rely on
bidirectional communications.
Included below is an excerpt from the APDA developer notes on the
LaserWriter Select 360 regarding the parallel port:
"The Centronics parallel interface is essentially an input-only channel.
This means it transfers information from the host to the printer. However,
the PostScript interpreter always deals with both the input and output
sides of an I/O channel. When operating in Centronics parallel input mode,
the printer sets up the 8-pin serial port for the PostScript language print
operator. The output from this port may be ignored for simple one-way
communication. However, important information may be output via this port.
Printer errors are always reported, since the Paper Error signal on the
Centronics interface cannot be relied upon to report all printer errors."
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