2 .\" Copyright (c) 2004 Jason L. Wright (jason@thought.net)
3 .\" Copyright (c) 2005 Marius Strobl <marius@FreeBSD.org>
4 .\" All rights reserved.
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
9 .\" 1. Redistributions of source code must retain the above copyright
10 .\" notice, this list of conditions and the following disclaimer.
11 .\" 2. Redistributions in binary form must reproduce the above copyright
12 .\" notice, this list of conditions and the following disclaimer in the
13 .\" documentation and/or other materials provided with the distribution.
15 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 .\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 .\" DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
19 .\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
20 .\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 .\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
23 .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
24 .\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 .\" POSSIBILITY OF SUCH DAMAGE.
27 .\" from: OpenBSD: clock.4,v 1.3 2004/09/24 07:04:15 miod Exp
35 .Nd "non-volatile RAM / real time clock"
43 driver is a front-end for the machine-independent
48 MK48Txx driver provides access to the real time clock and the watchdog part
49 of the supported chips to
51 by interfacing them with the generic clock code and
56 MK48Txx chips providing real time clock functionality are found on the
64 On systems where the hostid is stored in the NVRAM part of the
68 driver prints out the hostid on attach.
72 250 and 450 systems additionally the watchdog functionality of the
74 MK48Txx chips is available.
77 driver automatically registers the watchdog part with
80 Thus it can be used with
84 The timeout interval supported by the
86 MK48Txx watchdog is 1/16 second to 128 seconds.
89 machines a system reset is triggered when the
91 MK48Txx watchdog times out regardless of what the
97 The following driver specific error message may be reported:
99 .It "mk48txx_attach: battery low"
100 The device signals that its battery is low and should be replaced.
103 driver refused to attach the device in this case as the time in the real time
104 clock is probably invalid.
105 This gives the generic clock code the chance to use another device as the
106 system real time clock that otherwise would not have been chosen.
119 driver first appeared in
125 driver was written by
126 .An Thomas Moestl Aq Mt tmm@FreeBSD.org
129 sparc64 clock code written by
130 .An Paul Kranenburg .