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CM(4)			     Kernel Interfaces Manual			   CM(4)

NAME
     cm -- SMC Arcnet Ethernet device driver

SYNOPSIS
     To compile this driver into the kernel, place the following lines in your
     kernel configuration file:

	   device isa
	   device cm

     Alternatively, to load the driver as a module at boot time, place the
     following line in loader.conf(5):

	   if_cm_load="YES"

DESCRIPTION
     The cm driver provides support for the Arcnet ISA network adapters.

     This driver also has quirks preset in the device.hints(5) file for card de-
     tection.

HARDWARE
     The cm driver supports the following card models:

     *	 SMC90c26
     *	 SMC90c56
     *	 SMC90c66 in '56 compatibility mode.

IMPLEMENTATION NOTES
     When  the NOARP flag is set on the cm interface, it does not employ the ad-
     dress resolution protocol described in arp(4) to  dynamically  map  between
     Internet  and Ethernet addresses on the local network.  Instead it uses the
     least significant 8 bits of the IP address as the hardware address like de-
     scribed in RFC 1051 and RFC 1201.

     With the IFF_LINK0 flag cleared IP/ARP/RARP encoding is done  according  to
     RFC  1201 that is, with Packet Header Definition Standard header and packet
     type 212 / 213.  The MTU is normally 1500.  The IFF_LINK0 flag  is  cleared
     by default.

     With  the	IFF_LINK0 flag set, IP and ARP encoding is done according to the
     deprecated RFC 1051 encoding, that is with simple header, packet type 240 /
     241, and the MTU is 507.

     When switching between the two modes, use
	   ifconfig interfacename down up
     to switch the MTU.

DIAGNOSTICS
     The following driver specific error messages may be reported:

     reset: card reset, link addr = 0x%02x (cm%d)  The card is being reset and a
     new link address assigned.

     srint: restarted rx on buf cm%d  The rx buffer has been emptied and will be
     reset.

SEE ALSO
     netintro(4), watchdog(4), device.hints(5), ifconfig(8), watchdog(8)

HISTORY
     The cm device was ported from NetBSD by  Max  Khon  <fjoe@FreeBSD.org>  and
     first  appeared  in  FreeBSD  4.6.   This	manual	page  first  appeared in
     FreeBSD 5.3.

AUTHORS
     This manual page was written  by  Tom  Rhodes  <trhodes@FreeBSD.org>.   The
     "IMPLEMENTATION NOTES" section was submitted by
     Max Khon <fjoe@FreeBSD.org> and originated from NetBSD.

BUGS
     The  cm driver code could do with a bit of improvement, it would be nice if
     some one could come along and take care of this.

     The "IMPLEMENTATION NOTES" section is specific to all Arcnet  devices  (see
     sys/net/if_arcsubr.c) and should be moved to a more generic location.

FreeBSD 9.1			  July 16, 2005 			   CM(4)
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