EN(4)

NAME
en - 10 Mb/s Ethernet interface

DESCRIPTION
The en interface provides access to a 10 Mb/s Ethernet network through an Acorn Ethernet/Cheapernet expansion card used as a link-layer interface. It differs from the et(4) driver in that the et driver is for Ethernet cards which use Intel's 82856 “LANCE” controller, whereas the en driver is for cards built around National Semiconductor's DP8390C “NIC” chip.

Each of the host's internet network addresses is specified at boot time with an SIOCSIFADDR ioctl(). This is usually done with ifconfig(8).

The en interface employs the address resolution protocol described in arp(4P) to dynamically map between Internet and Ethernet addresses on the local network. The ethernet hardware address of the interface is obtained from a unique rom on the card and cannot be changed by software.

The use of a “trailer” encapsulation protocol is negotiated with ARP. This negotiation may be disabled, on a per-interface basis, by setting the IFF_NOTRAILERS flag with an SIOCSIFFLAGS ioctl. The interface normally tries to use trailer encapsulation to minimize copying data on input and output only if the other end of a connection has requested trailers.

DIAGNOSTICS
During a system boot, the en driver performs a power on self-test (“POST”), which can produce a range of diagnostic messages identifying various hardware problems with the card, e.g. remote DMA failure, bad CRC etc..

en%d: Ethernet is not connected. en%d: Ethernet is not terminated. The en driver was unable to run the POST because the cable was either not connected, or was improperly terminated. This is not a fatal error: every time an SIOCSIFADDR ioctl() is issued, a cable check is run again and, when it passes, the driver will run the POST; if this succeeds, the en driver will bring the interface up.

en%d: slot %d: rev %x, address %s. This is the welcome message printed during system boot when a card has not failed the POST (i.e. it has either passed, or the driver was unable to run the tests).

The following diagnostics only occur when enabled by “ifconfig en0 debug”. They indicate problems with packet reception, and/or transmission. For details refer to the National Semiconductor DP8390C programming manual.

en%d: Tx abort.

en%d: FIFO underrun.

en%d: receive error: FAE/CRC/FRL/FIFO overrun.

SEE ALSO
intro(4N), et(4), inet(4F), arp(4P), ifconfig(8)