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+Networking with HDLC
+====================
+
+Author: Andy Dachs <a.dachs@sstl.co.uk>
+Date:	31st August 2001
+Surrey Satellite Technology Limited
+
+
+The network support in this BSP is not Ethernet support. The
+"network" referred to here is a point to point HDLC communication link.
+The ADS board does have a 10/100 ethernet port and it would be nice to
+get support for that added.
+
+My requirement is for a WAN so I need the ability to send IP frames over
+HDLC.  Ultimately this will end up as frame relay support but in the meantime
+I'm simply wrapping up the IP packet inside an HDLC frame.  There is no
+addressing mechanism or mac address attached to the start of the frame.
+
+This is what is physically transmitted:
+<FLAG><IP Frame><CRC><FLAG>
+
+
+The physical link consists of four lines,
+TX DATA	:	Data transmitted
+TX CLOCK:	Clock for transmitted data.  Data source provides clock.
+RX DATA : 	Received data
+RX CLOCK:	Clock for received data.  Data sink accepts clock.
+
+To connect two entities you require a NULL modem arrangement, i.e. TX data
+and Tx clock from one end go into RX data and Rx clock on the other end.
+
+The MPC8260ADS side of the link is implemented using SCC3 in HDLC mode. The
+TX clock is generated by BRG4.  The RX clock in input to the board on the CLK5
+input.  I built a LVTTL to RS422 converter.
+
+The other end of the link is a Windows NT PC with WANic400 synchronous
+communication card.  We bought the card from ImageStream
+(http://www.imagestream.com/WANic400.html).  You also need the NT
+drivers and a cable.  There are other distributors but I found these
+guys helpful - and they also do Linux drivers.
+
+The NT WANic driver has a number of modes, one of which is ethernet emulation.
+This mode is what is needed to transport IP packets in HDLC frames.
+
+In libnetworking/net you will find a file called if_hdlcsubr.c containing
+the hdlc_input and hdlc_output routines required by network.c.  This file was
+created by taking out the addressing mechanisms from if_ethersubr.c in the
+same directory.  There are probably neater ways to do this <any
+contributions welcome here>.
+
+
+
+
+
+