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/*****
* S-RTC emulation code
* Copyright (c) byuu
*****/
#define _SRTCEMU_CPP_
const unsigned SRTC::months[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
void SRTC::power() {
reset();
}
void SRTC::reset() {
rtc_mode = RTCM_Read;
rtc_index = -1;
update_time();
}
void SRTC::update_time() {
time_t rtc_time
= (memory_cartrtc_read(16) << 0)
| (memory_cartrtc_read(17) << 8)
| (memory_cartrtc_read(18) << 16)
| (memory_cartrtc_read(19) << 24);
time_t current_time = time(0);
//sizeof(time_t) is platform-dependent; though memory::cartrtc needs to be platform-agnostic.
//yet platforms with 32-bit signed time_t will overflow every ~68 years. handle this by
//accounting for overflow at the cost of 1-bit precision (to catch underflow). this will allow
//memory::cartrtc timestamp to remain valid for up to ~34 years from the last update, even if
//time_t overflows. calculation should be valid regardless of number representation, time_t size,
//or whether time_t is signed or unsigned.
time_t diff
= (current_time >= rtc_time)
? (current_time - rtc_time)
: (std::numeric_limits<time_t>::max() - rtc_time + current_time + 1); //compensate for overflow
if(diff > std::numeric_limits<time_t>::max() / 2) diff = 0; //compensate for underflow
if(diff > 0) {
unsigned second = memory_cartrtc_read( 0) + memory_cartrtc_read( 1) * 10;
unsigned minute = memory_cartrtc_read( 2) + memory_cartrtc_read( 3) * 10;
unsigned hour = memory_cartrtc_read( 4) + memory_cartrtc_read( 5) * 10;
unsigned day = memory_cartrtc_read( 6) + memory_cartrtc_read( 7) * 10;
unsigned month = memory_cartrtc_read( 8);
unsigned year = memory_cartrtc_read( 9) + memory_cartrtc_read(10) * 10 + memory_cartrtc_read(11) * 100;
unsigned weekday = memory_cartrtc_read(12);
day--;
month--;
year += 1000;
second += diff;
while(second >= 60) {
second -= 60;
minute++;
if(minute < 60) continue;
minute = 0;
hour++;
if(hour < 24) continue;
hour = 0;
day++;
weekday = (weekday + 1) % 7;
unsigned days = months[month % 12];
if(days == 28) {
bool leapyear = false;
if((year % 4) == 0) {
leapyear = true;
if((year % 100) == 0 && (year % 400) != 0) leapyear = false;
}
if(leapyear) days++;
}
if(day < days) continue;
day = 0;
month++;
if(month < 12) continue;
month = 0;
year++;
}
day++;
month++;
year -= 1000;
memory_cartrtc_write( 0, second % 10);
memory_cartrtc_write( 1, second / 10);
memory_cartrtc_write( 2, minute % 10);
memory_cartrtc_write( 3, minute / 10);
memory_cartrtc_write( 4, hour % 10);
memory_cartrtc_write( 5, hour / 10);
memory_cartrtc_write( 6, day % 10);
memory_cartrtc_write( 7, day / 10);
memory_cartrtc_write( 8, month);
memory_cartrtc_write( 9, year % 10);
memory_cartrtc_write(10, (year / 10) % 10);
memory_cartrtc_write(11, year / 100);
memory_cartrtc_write(12, weekday % 7);
}
memory_cartrtc_write(16, current_time >> 0);
memory_cartrtc_write(17, current_time >> 8);
memory_cartrtc_write(18, current_time >> 16);
memory_cartrtc_write(19, current_time >> 24);
}
//returns day of week for specified date
//eg 0 = Sunday, 1 = Monday, ... 6 = Saturday
//usage: weekday(2008, 1, 1) returns weekday of January 1st, 2008
unsigned SRTC::weekday(unsigned year, unsigned month, unsigned day) {
unsigned y = 1900, m = 1; //epoch is 1900-01-01
unsigned sum = 0; //number of days passed since epoch
year = max(1900, year);
month = max(1, min(12, month));
day = max(1, min(31, day));
while(y < year) {
bool leapyear = false;
if((y % 4) == 0) {
leapyear = true;
if((y % 100) == 0 && (y % 400) != 0) leapyear = false;
}
sum += leapyear ? 366 : 365;
y++;
}
while(m < month) {
unsigned days = months[m - 1];
if(days == 28) {
bool leapyear = false;
if((y % 4) == 0) {
leapyear = true;
if((y % 100) == 0 && (y % 400) != 0) leapyear = false;
}
if(leapyear) days++;
}
sum += days;
m++;
}
sum += day - 1;
return (sum + 1) % 7; //1900-01-01 was a Monday
}
uint8 SRTC::mmio_read(unsigned addr) {
addr &= 0xffff;
if(addr == 0x2800) {
if(rtc_mode != RTCM_Read) return 0x00;
if(rtc_index < 0) {
update_time();
rtc_index++;
return 0x0f;
} else if(rtc_index > 12) {
rtc_index = -1;
return 0x0f;
} else {
return memory_cartrtc_read(rtc_index++);
}
}
return cpu_regs_mdr;
}
void SRTC::mmio_write(unsigned addr, uint8 data) {
addr &= 0xffff;
if(addr == 0x2801) {
data &= 0x0f; //only the low four bits are used
if(data == 0x0d) {
rtc_mode = RTCM_Read;
rtc_index = -1;
return;
}
if(data == 0x0e) {
rtc_mode = RTCM_Command;
return;
}
if(data == 0x0f) return; //unknown behavior
if(rtc_mode == RTCM_Write) {
if(rtc_index >= 0 && rtc_index < 12) {
memory_cartrtc_write(rtc_index++, data);
if(rtc_index == 12) {
//day of week is automatically calculated and written
unsigned day = memory_cartrtc_read( 6) + memory_cartrtc_read( 7) * 10;
unsigned month = memory_cartrtc_read( 8);
unsigned year = memory_cartrtc_read( 9) + memory_cartrtc_read(10) * 10 + memory_cartrtc_read(11) * 100;
year += 1000;
memory_cartrtc_write(rtc_index++, weekday(year, month, day));
}
}
} else if(rtc_mode == RTCM_Command) {
if(data == 0) {
rtc_mode = RTCM_Write;
rtc_index = 0;
} else if(data == 4) {
rtc_mode = RTCM_Ready;
rtc_index = -1;
for(unsigned i = 0; i < 13; i++) memory_cartrtc_write(i, 0);
} else {
//unknown behavior
rtc_mode = RTCM_Ready;
}
}
}
}
SRTC::SRTC() {
}
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