.\"	$NetBSD: mk48txx.4,v 1.13 2003/11/02 09:08:16 wiz Exp $
.\"
.\" Copyright (c) 2000, 2002 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Paul Kranenburg.
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.Dd November 1, 2003
.Dt MK48TXX 4
.Os
.Sh NAME
.Nm mk48txx
.Nd
.Tn Mostek
time-of-day clock driver
.Sh SYNOPSIS
.In dev/ic/mk48txxreg.h
.In dev/ic/mk48txxvar.h
.Cd "define mk48txx"
.Cd "file   dev/ic/mk48txx.c    mk48txx"
.Sh DESCRIPTION
The
.Nm
driver provides access to several models of
.Tn Mostek
time-of-day clock chips.
Access methods to retrieve and set date and time
are provided through the
.Em TODR
interface defined in
.Xr todr 9 .
.Pp
To tie an instance of this device to the system, use the
.Fn mk48txx_attach
function and the mk48txx_softc structure defined as follows:
.Pp
.nr nS 1
.Ft "void"
.Fn mk48txx_attach "struct mk48txx_softc"
.Pp
.Bd -literal
typedef uint8_t (*mk48txx_nvrd_t)(struct mk48txx_softc, int off);
typedef void (*mk48txx_nvwr_t)(struct mk48txx_softc, int off,
    uint8_t datum);
.Ed
.Bd -literal
struct mk48txx_softc {
	struct device   sc_dev;
	bus_space_tag_t sc_bst;
	bus_space_handle_t sc_bsh;
	struct todr_chip_handle sc_handle;
	const char	*sc_model;
	bus_size_t	sc_nvramsz;
	bus_size_t	sc_clkoffset;
	u_int		sc_year0;
	u_int		sc_flag;
	mk48txx_nvrd_t	sc_nvrd;
	mk48txx_nvwr_t	sc_nvwr;
};
.Ed
.Pp
.Bl -tag -width Dv -offset indent
.It Fa sc_bst
.It Fa sc_bsh
Specify bus space access to the chip's non-volatile memory
.Pq including the clock registers .
.It Fa sc_handle
TODR handle passed to the
.Fn todr_attach
function to register
.Xr todr 9
interface.
.It Fa sc_model
The chip model which this instance should serve.
Must be one of
.Dq mk48t02 ,
.Dq mk48t08 ,
.Dq mk48t18 ,
or
.Dq mk48t59 .
.It Fa sc_nvramsz
Size of non-volatile RAM in the
.Tn Mostek
chip.
This value is set by
.Fn mk48txx_attach .
.It Fa sc_clkoffset
Offset into the control registers of the
.Tn Mostek
chip.
This value is set by
.Fn mk48txx_attach .
.It Fa sc_year0
The actual year represented by the clock's
.Sq year
counter.
This is generally dependent on the system configuration in which
the clock device is mounted.
For instance, on
.Tn Sun Microsystems
machines the convention is to have clock's two-digit year represent
the year 1968.
.It Fa sc_flag
This flag is used to specify machine-dependent features.
.It Fa sc_nvread
.It Fa sc_nvwrite
Specify alternate access methods for reading resp. writing clock
device registers.
The default, when
.Dv NULL
is passed as an access method, is to access the chip memory
.Pq and clock registers
as if they were direct-mapped with using the specified bus space.
.Pp
Otherwise, the driver will call the respective function to perform the
access, passing it the specified bus space and the offset
.Va off
of the chip memory
.Pq or clock register
location to be read from or written to, respectively.
.El
.Pp
Note that if the resulting date retrieved with the todr_gettime() method
is earlier that January 1, 1970, the driver will assume that the chip's
year counter actually represents a year in the 21st century.
This behaviour can be overridden by setting the
.Va MK48TXX_NO_CENT_ADJUST
flag in
.Fa sc_flag .
.Sh HARDWARE
The following models are supported:
.Pp
.Bl -tag -width indent -offset indent -compact
.It Tn Mostek MK48T02
.It Tn Mostek MK48T08
.It Tn Mostek MK48T18
.It Tn Mostek MK48T59
.El
.Sh SEE ALSO
.Xr intro 4 ,
.Xr todr 9
.Sh HISTORY
The
.Nm mk48txx
driver first appeared in
.Nx 1.5 .
.Sh AUTHORS
The
.Nm
driver was written by
.An Paul Kranenburg
.Aq pk@NetBSD.org .