source: rtems/c/src/lib/libbsp/powerpc/mpc8260ads/network/README @ 2d0bc83

Last change on this file since 2d0bc83 was 5edbffe, checked in by Joel Sherrill <joel.sherrill@…>, on Oct 22, 2001 at 2:46:02 PM

01-10-22 Andy Dachs <a.dachs@…>

  • mpc8260ads added as new BSP. tm27 reported not to run at this time.
  • ChangeLog?, Makefile.am, README, aclocal.m4, bsp_specs, clock/.cvsignore, clock/Makefile.am, clock/p_clock.c, configure.in, console/Makefile.am, console/console.c, include/Makefile.am, include/bsp.h, include/coverhd.h, irq/.cvsignore, irq/Makefile.am, irq/irq.c, irq/irq.h, irq/irq_asm.S, irq/irq_init.c, network/Makefile.am, network/README, network/if_hdlcsubr.c, network/if_hdlcsubr.h, network/network.c, start/Makefile.am, start/start.S, startup/Makefile.am, startup/bspstart.c, startup/cpuinit.c, startup/linkcmds, startup/setvec.c, times, vectors/.cvsignore, vectors/Makefile.am, vectors/vectors.S, vectors/vectors.h, vectors/vectors_init.c, wrapup/Makefile.am: New files.
  • Property mode set to 100644
File size: 2.1 KB
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1Networking with HDLC
2====================
3
4Author: Andy Dachs <a.dachs@sstl.co.uk>
5Date:   31st August 2001
6Surrey Satellite Technology Limited
7
8
9The network support in this BSP is not Ethernet support. The
10"network" referred to here is a point to point HDLC communication link.
11The ADS board does have a 10/100 ethernet port and it would be nice to
12get support for that added.
13
14My requirement is for a WAN so I need the ability to send IP frames over
15HDLC.  Ultimately this will end up as frame relay support but in the meantime
16I'm simply wrapping up the IP packet inside an HDLC frame.  There is no
17addressing mechanism or mac address attached to the start of the frame.
18
19This is what is physically transmitted:
20<FLAG><IP Frame><CRC><FLAG>
21
22
23The physical link consists of four lines,
24TX DATA :       Data transmitted
25TX CLOCK:       Clock for transmitted data.  Data source provides clock.
26RX DATA :       Received data
27RX CLOCK:       Clock for received data.  Data sink accepts clock.
28
29To connect two entities you require a NULL modem arrangement, i.e. TX data
30and Tx clock from one end go into RX data and Rx clock on the other end.
31
32The MPC8260ADS side of the link is implemented using SCC3 in HDLC mode. The
33TX clock is generated by BRG4.  The RX clock in input to the board on the CLK5
34input.  I built a LVTTL to RS422 converter.
35
36The other end of the link is a Windows NT PC with WANic400 synchronous
37communication card.  We bought the card from ImageStream
38(http://www.imagestream.com/WANic400.html).  You also need the NT
39drivers and a cable.  There are other distributors but I found these
40guys helpful - and they also do Linux drivers.
41
42The NT WANic driver has a number of modes, one of which is ethernet emulation.
43This mode is what is needed to transport IP packets in HDLC frames.
44
45In libnetworking/net you will find a file called if_hdlcsubr.c containing
46the hdlc_input and hdlc_output routines required by network.c.  This file was
47created by taking out the addressing mechanisms from if_ethersubr.c in the
48same directory.  There are probably neater ways to do this <any
49contributions welcome here>.
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