112 lines
3.4 KiB
C++
112 lines
3.4 KiB
C++
#include "time.h"
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// Set by ACPI table parsing code if possible
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int century_register = 0x00;
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unsigned char second;
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unsigned char minute;
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unsigned char hour;
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unsigned char day;
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unsigned char month;
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unsigned int year;
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int get_update_in_progress_flag() {
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outb(cmos_address, 0x0A);
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return (inb(cmos_data) & 0x80);
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}
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unsigned char get_RTC_register(int reg) {
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outb(cmos_address, reg);
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return inb(cmos_data);
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}
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void read_rtc() {
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unsigned char century;
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unsigned char last_second;
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unsigned char last_minute;
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unsigned char last_hour;
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unsigned char last_day;
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unsigned char last_month;
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unsigned char last_year;
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unsigned char last_century;
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unsigned char registerB;
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// Note: This uses the "read registers until you get the same values twice in a row" technique
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// to avoid getting dodgy/inconsistent values due to RTC updates
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while (get_update_in_progress_flag()); // Make sure an update isn't in progress
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second = get_RTC_register(0x00);
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minute = get_RTC_register(0x02);
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hour = get_RTC_register(0x04);
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day = get_RTC_register(0x07);
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month = get_RTC_register(0x08);
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year = get_RTC_register(0x09);
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if(century_register != 0) {
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century = get_RTC_register(century_register);
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} else {
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century = 21;
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}
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do {
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last_second = second;
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last_minute = minute;
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last_hour = hour;
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last_day = day;
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last_month = month;
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last_year = year;
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last_century = century;
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while (get_update_in_progress_flag()); // Make sure an update isn't in progress
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second = get_RTC_register(0x00);
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minute = get_RTC_register(0x02);
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hour = get_RTC_register(0x04);
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day = get_RTC_register(0x07);
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month = get_RTC_register(0x08);
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year = get_RTC_register(0x09);
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if(century_register != 0) {
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century = get_RTC_register(century_register);
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}
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} while( (last_second != second) || (last_minute != minute) || (last_hour != hour) ||
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(last_day != day) || (last_month != month) || (last_year != year) ||
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(last_century != century) );
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registerB = get_RTC_register(0x0B);
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// Convert BCD to binary values if necessary
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if (!(registerB & 0x04)) {
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second = (second & 0x0F) + ((second / 16) * 10);
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minute = (minute & 0x0F) + ((minute / 16) * 10);
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hour = ( (hour & 0x0F) + (((hour & 0x70) / 16) * 10) ) | (hour & 0x80);
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day = (day & 0x0F) + ((day / 16) * 10);
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month = (month & 0x0F) + ((month / 16) * 10);
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year = (year & 0x0F) + ((year / 16) * 10);
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if(century_register != 0) {
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century = (century & 0x0F) + ((century / 16) * 10);
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}
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}
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// Convert 12 hour clock to 24 hour clock if necessary
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if (!(registerB & 0x02) && (hour & 0x80)) {
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hour = ((hour & 0x7F) + 12) % 24;
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}
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// Calculate the full (4-digit) year
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if(century_register != 0) {
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year += century * 100;
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} else {
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year += (CURRENT_YEAR / 100) * 100;
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if(year < CURRENT_YEAR) year += 100;
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}
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}
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void delay(int t){
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volatile int i,j;
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for(i=0;i<t;i++)
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for(j=0;j<25000;j++)
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asm("NOP");
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}
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