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    /* mc146818rtc.h - register definitions for the Real-Time-Clock / CMOS RAM
     * Copyright Torsten Duwe <duwe@informatik.uni-erlangen.de> 1993
     * derived from Data Sheet, Copyright Motorola 1984 (!).
     * It was written to be part of the Linux operating system.
     */
    /* permission is hereby granted to copy, modify and redistribute this code
     * in terms of the GNU Library General Public License, Version 2 or later,
     * at your option.
     */
    
    #ifndef _MC146818RTC_H
    #define _MC146818RTC_H
    
    #include <asm/io.h>
    #include <linux/rtc.h>          /* get the user-level API */
    #include <asm/mc146818rtc.h>        /* register access macros */
    
    /**********************************************************************
     * register summary
     **********************************************************************/
    #define RTC_SECONDS     0
    #define RTC_SECONDS_ALARM   1
    #define RTC_MINUTES     2
    #define RTC_MINUTES_ALARM   3
    #define RTC_HOURS       4
    #define RTC_HOURS_ALARM     5
    /* RTC_*_alarm is always true if 2 MSBs are set */
    # define RTC_ALARM_DONT_CARE    0xC0
    
    #define RTC_DAY_OF_WEEK     6
    #define RTC_DAY_OF_MONTH    7
    #define RTC_MONTH       8
    #define RTC_YEAR        9
    
    /* control registers - Moto names
     */
    #define RTC_REG_A       10
    #define RTC_REG_B       11
    #define RTC_REG_C       12
    #define RTC_REG_D       13
    
    /**********************************************************************
     * register details
     **********************************************************************/
    #define RTC_FREQ_SELECT RTC_REG_A
    
    /* update-in-progress  - set to "1" 244 microsecs before RTC goes off the bus,
     * reset after update (may take 1.984ms @ 32768Hz RefClock) is complete,
     * totalling to a max high interval of 2.228 ms.
     */
    # define RTC_UIP        0x80
    # define RTC_DIV_CTL        0x70
       /* divider control: refclock values 4.194 / 1.049 MHz / 32.768 kHz */
    #  define RTC_REF_CLCK_4MHZ 0x00
    #  define RTC_REF_CLCK_1MHZ 0x10
    #  define RTC_REF_CLCK_32KHZ    0x20
       /* 2 values for divider stage reset, others for "testing purposes only" */
    #  define RTC_DIV_RESET1    0x60
    #  define RTC_DIV_RESET2    0x70
      /* Periodic intr. / Square wave rate select. 0=none, 1=32.8kHz,... 15=2Hz */
    # define RTC_RATE_SELECT    0x0F
    
    /**********************************************************************/
    #define RTC_CONTROL RTC_REG_B
    # define RTC_SET 0x80       /* disable updates for clock setting */
    # define RTC_PIE 0x40       /* periodic interrupt enable */
    # define RTC_AIE 0x20       /* alarm interrupt enable */
    # define RTC_UIE 0x10       /* update-finished interrupt enable */
    # define RTC_SQWE 0x08      /* enable square-wave output */
    # define RTC_DM_BINARY 0x04 /* all time/date values are BCD if clear */
    # define RTC_24H 0x02       /* 24 hour mode - else hours bit 7 means pm */
    # define RTC_DST_EN 0x01    /* auto switch DST - works f. USA only */
    
    /**********************************************************************/
    #define RTC_INTR_FLAGS  RTC_REG_C
    /* caution - cleared by read */
    # define RTC_IRQF 0x80      /* any of the following 3 is active */
    # define RTC_PF 0x40
    # define RTC_AF 0x20
    # define RTC_UF 0x10
    
    /**********************************************************************/
    #define RTC_VALID   RTC_REG_D
    # define RTC_VRT 0x80       /* valid RAM and time */
    /**********************************************************************/
    
    /* example: !(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
     * determines if the following two #defines are needed
     */
    #ifndef BCD_TO_BIN
    #define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
    #endif
    
    #ifndef BIN_TO_BCD
    #define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)
    #endif
    
    #endif /* _MC146818RTC_H */