CM(4)

NAME

     cm -- SMC Arcnet Ethernet device driver

SYNOPSIS

     device isa
     device cm

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
     detection.

HARDWARE

     The cm driver supports the following card models:

     +o	 SMC90c26
     +o	 SMC90c56
     +o	 SMC90c66 in '56 compatibility mode.

IMPLEMENTATION NOTES

     When the NOARP flag is set on the cm interface, it does not employ the
     address 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 described 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.