rtc.c

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/* Xep128: Minimalistic Enterprise-128 emulator with focus on "exotic" hardware
   Copyright (C)2015,2016 LGB (Gábor Lénárt) <lgblgblgb@gmail.com>
   http://xep128.lgb.hu/
 
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
 
#include "xep128.h"
#include "rtc.h"
 
#include "main.h"
 
#include <time.h>
 
 
//#define RESET_RTC_INDEX
 
 
static int _rtc_register;
static Uint8 cmos_ram[0x100];
int rtc_update_trigger;
 
 
void rtc_set_reg(Uint8 val)
{
        _rtc_register = val;
        DEBUG("RTC: register number %02X has been selected" NL, val);
}
 
 
void rtc_write_reg(Uint8 val)
{
        DEBUG("RTC: write reg %02X with data %02X" NL, _rtc_register, val);
        if (_rtc_register == 0xC || _rtc_register == 0xD) return;
        if (_rtc_register == 0xA) val &= 127;
        cmos_ram[_rtc_register] = val;
#ifdef RESET_RTC_INDEX
        _rtc_register = 0xD;
#endif
}
 
 
static int _rtc_conv(int bin, int is_hour)
{
        int b7 = 0;
        if (is_hour && (!(cmos_ram[0xB] & 2))) { // AM/PM
                if (bin == 0) {
                        bin = 12;
                } else if (bin == 12) {
                        b7 = 128;
                } else if (bin > 12) {
                        bin -= 12;
                        b7 = 128;
                }
        }
        if (!(cmos_ram[0xB] & 4)) { // do bin->bcd
                bin = ((bin / 10) << 4) | (bin % 10);
        }
        return bin | b7;
}
 
 
static void _rtc_update(void)
{
        struct tm *t = localtime(&unix_time);
        cmos_ram[   0] = _rtc_conv(t->tm_sec, 0);
        cmos_ram[   2] = _rtc_conv(t->tm_min, 0);
        cmos_ram[   4] = _rtc_conv(t->tm_hour, 1);
        cmos_ram[   6] = _rtc_conv(t->tm_wday + 1, 0);  // day, 1-7 (week)
        cmos_ram[   7] = _rtc_conv(t->tm_mday, 0); // date, 1-31
        cmos_ram[   8] = _rtc_conv(t->tm_mon + 1, 0); // month, 1 -12
        cmos_ram[   9] = _rtc_conv((t->tm_year % 100) + 20, 0); // year, 0 - 99
        cmos_ram[0x32] = _rtc_conv(21, 0); // century???
        DEBUG("RTC: time/date has been updated for \"%d-%02d-%02d %02d:%02d:%02d\" at UNIX epoch %ld" NL,
                t->tm_year + 1900,
                t->tm_mon + 1,
                t->tm_mday,
                t->tm_hour,
                t->tm_min,
                t->tm_sec,
                (long int)unix_time
        );
}
 
 
void rtc_reset(void)
{
        memset(cmos_ram, 0, 0x100);
        _rtc_register = 0xD;
        rtc_update_trigger = 0;
        cmos_ram[0xA] = 32;
        cmos_ram[0xB] = 2; // 2 | 4;
        cmos_ram[0xC] = 0;
        cmos_ram[0xD] = 128;
        DEBUG("RTC: reset" NL);
        _rtc_update();
}
 
 
Uint8 rtc_read_reg(void)
{
        int i = _rtc_register;
#ifdef RESET_RTC_INDEX
        _rtc_register = 0xD;
#endif
        if (i > 63)
                return 0xFF;
        if (rtc_update_trigger && (cmos_ram[0xB] & 128) == 0 && i < 10) {
                _rtc_update();
                rtc_update_trigger = 0;
        }
        DEBUG("RTC: reading register %02X, result will be: %02X" NL, i, cmos_ram[i]);
        return cmos_ram[i];
}