.\"-
.\" Copyright (c) 2004 Jason L. Wright (jason@thought.net)
.\" Copyright (c) 2005 Marius Strobl <marius@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
.\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
.\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.\"	from: OpenBSD: clock.4,v 1.3 2004/09/24 07:04:15 miod Exp
.\" $FreeBSD$
.\"
.Dd June 18, 2005
.Dt RTC 4 sparc64
.Os
.Sh NAME
.Nm rtc
.Nd "non-volatile RAM / real time clock"
.Sh SYNOPSIS
.Cd "device genclock"
.Cd "device mc146818"
.Cd "device rtc"
.Sh DESCRIPTION
The
.Nm
driver is a front-end for the machine-independent
.Tn Motorola
MC146818 and compatible clocks driver.
The
.Tn Motorola
MC146818 and compatible clocks driver provides access to the real time clock
part of the chips it supports to
.Fx
by interfacing with the generic clock code.
.Pp
.Tn Dallas /
.Tn Maxim Semiconductor
DS1287 chips
(those are compatible to the
.Tn Motorola
MC146818 clocks)
are found on the ISA bus of
.Tn UltraSPARC II
systems and the EBus bus of
.Tn UltraSPARC III
systems.
.Sh DIAGNOSTICS
The following driver specific error message may be reported:
.Bl -diag
.It "mc146818_attach_attach: battery low"
The device signals that its battery is low and should be replaced.
The
.Nm
driver refused to attach the device in this case as the time in the real time
clock is probably invalid.
This gives the generic clock code the chance to use another device as the
system real time clock that otherwise would not have been chosen.
.El
.Sh SEE ALSO
.Xr ebus 4 ,
.Xr eeprom 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 5.4 .
.Sh AUTHORS
The
.Nm
driver was written by
.An Marius Strobl Aq Mt marius@FreeBSD.org .