MK48TXX(4)              NetBSD Kernel Interfaces Manual             MK48TXX(4)

     mk48txx -- Mostek time-of-day clock driver

     #include <dev/ic/mk48txxreg.h>
     #include <dev/ic/mk48txxvar.h>
     define mk48txx
     file   dev/ic/mk48txx.c    mk48txx

     The mk48txx driver provides access to several models of Mostek time-of-
     day clock chips.  Access methods to retrieve and set date and time are
     provided through the TODR interface defined in todr(9).

     To tie an instance of this device to the system, use the mk48txx_attach()
     function and the mk48txx_softc structure defined as follows:

     void mk48txx_attach(struct mk48txx_softc *)

     typedef uint8_t (*mk48txx_nvrd_t)(struct mk48txx_softc *, int off);
     typedef void (*mk48txx_nvwr_t)(struct mk48txx_softc *, int off,
         uint8_t datum);

     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;


           sc_bsh        Specify bus space access to the chip's non-volatile
                         memory (including the clock registers).

           sc_handle     TODR handle passed to the todr_attach() function to
                         register todr(9) interface.

           sc_model      The chip model which this instance should serve.
                         Must be one of ``mk48t02'', ``mk48t08'', ``mk48t18'',
                         or ``mk48t59''.

           sc_nvramsz    Size of non-volatile RAM in the Mostek chip.  This
                         value is set by mk48txx_attach().

           sc_clkoffset  Offset into the control registers of the Mostek chip.
                         This value is set by mk48txx_attach().

           sc_year0      The actual year represented by the clock's `year'
                         counter.  This is generally dependent on the system
                         configuration in which the clock device is mounted.
                         For instance, on Sun Microsystems machines the con-
                         vention is to have clock's two-digit year represent
                         the year 1968.

           sc_flag       This flag is used to specify machine-dependent fea-


           sc_nvwrite    Specify alternate access methods for reading resp.
                         writing clock device registers.  The default, when
                         NULL is passed as an access method, is to access the
                         chip memory (and clock registers) as if they were
                         direct-mapped with using the specified bus space.

                         Otherwise, the driver will call the respective func-
                         tion to perform the access, passing it the specified
                         bus space and the offset off of the chip memory (or
                         clock register) location to be read from or written
                         to, respectively.

     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 behav-
     iour can be overridden by setting the MK48TXX_NO_CENT_ADJUST flag in

     The following models are supported:

           Mostek MK48T02
           Mostek MK48T08
           Mostek MK48T18
           Mostek MK48T59

     intro(4), todr(9)

     The mk48txx driver first appeared in NetBSD 1.5.

     The mk48txx driver was written by Paul Kranenburg <>.

NetBSD 5.0.1                    October 1, 2006                   NetBSD 5.0.1

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