📄 introduction to the ieee 1284-1994 standard.htm
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href="http://www.fapo.com/bytemode.htm">Byte Mode</A></FONT>
<DD><FONT face="Arial, Helvetica, sans-serif" color=#000000 size=1>8
bits at a time using data lines, sometimes referred to as a
"bi-directional" port.</FONT> </DD></DL>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1><STRONG>Bi-directional</STRONG></FONT>
<DL>
<DT><FONT face="Arial, Helvetica, sans-serif" color=#000000 size=1><A
href="http://www.fapo.com/eppmode.htm">EPP</A></FONT>
<DD><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Enhanced Parallel Port- used primarily by non-printer
peripherals, CD ROM, tape, hard drive, network adapters,
etc....</FONT>
<DT><FONT face="Arial, Helvetica, sans-serif" color=#000000 size=1><A
href="http://www.fapo.com/ecpmode.htm">ECP</A></FONT>
<DD><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Extended Capability Port- used primarily by new generation of
printers and scanners</FONT> </DD></DL></LI></UL></DIV>
<P align=left><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>All parallel ports can implement a bi-directional link by using the
Compatible and Nibble modes for data transfer. Byte mode can be utilized
by about 25% of the installed base of parallel ports. All three of these
modes utilize software only to transfer the data. The driver has to write
the data, check the handshake lines (i.e.: BUSY), assert the appropriate
control signals (i.e.: STROBE) and then go on to the next byte. This is
very software intensive and limits the effective data transfer rate to 50
to 100 Kbytes per second. </FONT></P>
<P align=left><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>In addition to the previous 3 modes, EPP and ECP are being
implemented on the latest I/O controllers by most of the Super I/O chip
manufacturers. These modes use hardware to assist in the data transfer.
For example, in EPP mode, a byte of data can be transferred to the
peripheral by a simple OUT instruction. The I/O controller handles all the
handshaking and data transfer to the peripheral. </FONT></P>
<P align=left><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Overall, the 1284 standard provides the following: </FONT>
<DIV align=left>
<OL>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000 size=1>5
modes of operation for data transfer</FONT>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000 size=1>A
method for the host and peripheral to determine the supported modes and
to <A href="http://www.fapo.com/negoti8.htm">negotiate</A> to the
requested mode.</FONT>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Defines the physical interface</FONT>
<UL>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000 size=1><A
href="http://www.fapo.com/1284cabl.htm">Cables</A></FONT>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000 size=1><A
href="http://www.fapo.com/1284conn.htm">Connectors</A></FONT> </LI></UL>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Defines the<A href="http://www.fapo.com/1284elec.htm"> electrical
interface</A></FONT>
<UL>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Drivers/Receivers</FONT>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Termination</FONT>
<LI><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>Impedance</FONT> </LI></UL></LI></OL></DIV>
<P align=left><FONT face="Arial, Helvetica, sans-serif" color=#000000
size=1>In summary, the 1284 parallel port provides an easy to use, high
performance interface for portable products and printers.</FONT></P>
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