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BSD 4.3tahoe

.\" Copyright (c) 1986 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)enp.4	5.1 (Berkeley) 12/12/87
.\"
.TH ENP 4 "April 29, 1987"
.UC 5
.SH NAME
enp \- CMC 10 Mb/s Ethernet interface
.SH SYNOPSIS
.B "device enp0 at vba? csr 0xfff40000 vector enpintr"
.SH DESCRIPTION
The
.I enp
interface provides access to a 10 Mb/s Ethernet network through
a CMC ENP-20 controller.
.PP
The hardware has 128 kilobytes of dual-ported memory on the VERSAbus. 
This memory
is used for internal buffering by the board, and the interface code reads
the buffer contents directly through the VERSAbus.
The address of this memory is derived from the address specified
in the configuration file.
.PP
Each of the host's network addresses
is specified at boot time with an SIOCSIFADDR
ioctl.  The
.I ace
interface employs the address resolution protocol described in
.IR arp (4P)
to dynamically map between Internet and Ethernet addresses on the local
network.
.PP
The interface normally tries to use a ``trailer'' encapsulation
to minimize copying data on input and output.
The use of trailers is negotiated with ARP.
This negotiation may be disabled, on a per-interface basis,
by setting the IFF_NOTRAILERS
flag with an SIOCSIFFLAGS ioctl.
.PP
Associated with each interface is a character device which
is used to dowload, start, and reset the firmware in the controller.
Reading or writing the ``ram device'' reads or writes the writable
control store in the controller.  Two
.IR ioctl (2)
calls, ENPIOGO and ENPIORESET, are used to start and reset the
firmware.
.SH DIAGNOSTICS
.BR "enp%d: can't handle af%d" .
The interface was handed
a message with addresses formatted in an unsuitable address
family; the packet was dropped.
.SH SEE ALSO
intro(4N), inet(4F), arp(4P), enpload(8C)
.SH BUGS
The hardware is not capable of talking to itself.  The software
implements local sending and broadcast by sending such packets to the
loop interface.  This is a kludge.
.PP
The link level firmware does not support setting the board's
Ethernet address.

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