BarinkOS/source/kernel/time.cpp

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