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Description / Abstract:
This standard denes a signaling method for asynchronous, fully
interlocked, bidirectional parallel communications between hosts
and printers or other peripherals. A functional subset of the
signaling method may be implemented on personal computers (PCs) or
equivalent parallel port hardware with new software. This standard
recommends new electrical interfaces, cabling, and interface
hardware that provides improved performance while retaining
backward compatibility with this subset.
This standard also specifies a format for a peripheral
identication string and a method of returning this string to the
host outside of the bidirectional data stream.
Purpose
This standard was created because there existed no dened
standard for bidirectional parallel communications between personal
computers and printing peripherals. Pre-existing methods utilized a
wide variety of hardware and software products, each with unique
and incompatible signaling schemes. This standard was developed to
provide an open path for communications between computers and more
intelligent printers and peripherals. The availability of a
standard bidirectional protocol will encourage the development of
new peripherals that return signicant data, as well as basic
status, to the host.