usr/src/sys/h/clock.h

/*      clock.h 4.1     11/9/80 */

/*
 * VAX clock registers
 */

#define ICCS_RUN        0x1
#define ICCS_TRANS      0x10
#define ICCS_SS         0x20
#define ICCS_IE         0x40
#define ICCS_INT        0x80
#define ICCS_ERR        0x80000000

#define SECDAY          ((unsigned)(24*60*60))          /* seconds per day */
#define SECYR           ((unsigned)(365*SECDAY))        /* per common year */
/*
 * TODRZERO is the what the TODR should contain when the ``year'' begins.
 * The TODR should always contain a number between 0 and SECYR+SECDAY.
 */
#define TODRZERO        ((unsigned)(1<<28))

#define YRREF           1970
#define LEAPYEAR(year)  ((year)%4==0 && year != 2000)   /* good till 2100 */

/*
 * Start a 60 HZ clock.
 */
#define clkstart() {\
        mtpr(NICR, -16667);     /* 16.667 milli-seconds */\
        mtpr(ICCS, ICCS_RUN+ICCS_IE+ICCS_TRANS+ICCS_INT+ICCS_ERR);\
}
#define clkreld()       mtpr(ICCS, ICCS_RUN+ICCS_IE+ICCS_INT+ICCS_ERR)

#define clkwrap()       (((unsigned)mfpr(TODR) - TODRZERO)/100 > SECYR+SECDAY)