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Merge branch 'fix-rtc2'
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@deltabeard
deltabeard committed Dec 23, 2023
2 parents b0660f4 + f6ed3b7 commit 97548ef
Showing 1 changed file with 91 additions and 54 deletions.
145 changes: 91 additions & 54 deletions peanut_gb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Please note that at least three parts of source code within this project was
* Please note that at least two parts of source code within this project was
* taken from the SameBoy project at https://github.com/LIJI32/SameBoy/ which at
* the time of this writing is released under the MIT License. Occurrences of
* this code is marked as being taken from SameBoy with a comment.
Expand Down Expand Up @@ -156,6 +156,9 @@
#define SCREEN_REFRESH_CYCLES 70224.0
#define VERTICAL_SYNC (DMG_CLOCK_FREQ/SCREEN_REFRESH_CYCLES)

/* Real Time Clock is locked to 1Hz. */
#define RTC_CYCLES ((unsigned long)DMG_CLOCK_FREQ)

/* SERIAL SC register masks. */
#define SERIAL_SC_TX_START 0x80
#define SERIAL_SC_CLOCK_SRC 0x01
Expand Down Expand Up @@ -435,6 +438,7 @@ struct count_s
uint_fast16_t div_count; /* Divider Register Counter */
uint_fast16_t tima_count; /* Timer Counter */
uint_fast16_t serial_count; /* Serial Counter */
uint_fast32_t rtc_count; /* RTC Counter */
};

#if ENABLE_LCD
Expand Down Expand Up @@ -492,6 +496,19 @@ enum gb_serial_rx_ret_e
GB_SERIAL_RX_NO_CONNECTION = 1
};

union cart_rtc
{
struct
{
uint8_t sec;
uint8_t min;
uint8_t hour;
uint8_t yday;
uint8_t high;
} reg;
uint8_t bytes[5];
};

/**
* Emulator context.
*
Expand Down Expand Up @@ -568,18 +585,8 @@ struct gb_s
uint8_t enable_cart_ram;
/* Cartridge ROM/RAM mode select. */
uint8_t cart_mode_select;
union
{
struct
{
uint8_t sec;
uint8_t min;
uint8_t hour;
uint8_t yday;
uint8_t high;
} rtc_bits;
uint8_t cart_rtc[5];
};

union cart_rtc rtc_latched, rtc_real;

struct cpu_registers_s cpu_reg;
//struct gb_registers_s gb_reg;
Expand Down Expand Up @@ -740,7 +747,7 @@ uint8_t __gb_read(struct gb_s *gb, uint16_t addr)
case 0xB:
if(gb->mbc == 3 && gb->cart_ram_bank >= 0x08)
{
return gb->cart_rtc[gb->cart_ram_bank - 0x08];
return gb->rtc_latched.bytes[gb->cart_ram_bank - 0x08];
}
else if(gb->cart_ram && gb->enable_cart_ram)
{
Expand Down Expand Up @@ -894,7 +901,11 @@ void __gb_write(struct gb_s *gb, uint_fast16_t addr, uint8_t val)

case 0x6:
case 0x7:
gb->cart_mode_select = (val & 1);
val &= 1;
if(gb->mbc == 3 && val && gb->cart_mode_select == 0)
memcpy(&gb->rtc_latched.bytes, &gb->rtc_real.bytes, sizeof(gb->rtc_latched.bytes));

gb->cart_mode_select = val;
return;

case 0x8:
Expand All @@ -906,7 +917,13 @@ void __gb_write(struct gb_s *gb, uint_fast16_t addr, uint8_t val)
case 0xB:
if(gb->mbc == 3 && gb->cart_ram_bank >= 0x08)
{
gb->cart_rtc[gb->cart_ram_bank - 0x08] = val;
const uint8_t rtc_reg_mask[5] = {
0x3F, 0x3F, 0x1F, 0xFF, 0xC1
};
uint8_t reg = gb->cart_ram_bank - 0x08;
//if(reg == 0) gb->counter.rtc_count = 0;

gb->rtc_real.bytes[reg] = val & rtc_reg_mask[reg];
}
/* Do not write to RAM if unavailable or disabled. */
else if(gb->cart_ram && gb->enable_cart_ram)
Expand Down Expand Up @@ -3233,6 +3250,53 @@ void __gb_step_cpu(struct gb_s *gb)
gb->counter.div_count -= DIV_CYCLES;
}

/* Check for RTC tick. */
if(gb->mbc == 3 && (gb->rtc_real.reg.high & 0x40) == 0)
{
gb->counter.rtc_count += inst_cycles;
while(gb->counter.rtc_count >= RTC_CYCLES)
{
gb->counter.rtc_count -= RTC_CYCLES;

/* Detect invalid rollover. */
if(gb->rtc_real.reg.sec == 63)
{
gb->rtc_real.reg.sec = 0;
continue;
}

if(++gb->rtc_real.reg.sec != 60)
continue;

gb->rtc_real.reg.sec = 0;
if(gb->rtc_real.reg.min == 63)
{
gb->rtc_real.reg.min = 0;
continue;
}
if(++gb->rtc_real.reg.min != 60)
continue;

gb->rtc_real.reg.min = 0;
if(gb->rtc_real.reg.hour == 31)
{
gb->rtc_real.reg.hour = 0;
continue;
}
if(++gb->rtc_real.reg.hour != 24)
continue;

gb->rtc_real.reg.hour = 0;
if(++gb->rtc_real.reg.yday != 0)
continue;

if(gb->rtc_real.reg.high & 1) /* Bit 8 of days*/
gb->rtc_real.reg.high |= 0x80; /* Overflow bit */

gb->rtc_real.reg.high ^= 1;
}
}

/* Check serial transmission. */
if(gb->hram_io[IO_SC] & SERIAL_SC_TX_START)
{
Expand Down Expand Up @@ -3520,6 +3584,7 @@ void gb_reset(struct gb_s *gb)
gb->counter.div_count = 0;
gb->counter.tima_count = 0;
gb->counter.serial_count = 0;
gb->counter.rtc_count = 0;

gb->direct.joypad = 0xFF;
gb->hram_io[IO_JOYP] = 0xCF;
Expand Down Expand Up @@ -3684,47 +3749,21 @@ void gb_set_bootrom(struct gb_s *gb,
}

/**
* This was taken from SameBoy, which is released under MIT Licence.
* Deprecated. Will be removed in the next major version.
*/
void gb_tick_rtc(struct gb_s *gb)
{
/* is timer running? */
if((gb->cart_rtc[4] & 0x40) == 0)
{
if(++gb->rtc_bits.sec == 60)
{
gb->rtc_bits.sec = 0;

if(++gb->rtc_bits.min == 60)
{
gb->rtc_bits.min = 0;

if(++gb->rtc_bits.hour == 24)
{
gb->rtc_bits.hour = 0;

if(++gb->rtc_bits.yday == 0)
{
if(gb->rtc_bits.high & 1) /* Bit 8 of days*/
{
gb->rtc_bits.high |= 0x80; /* Overflow bit */
}

gb->rtc_bits.high ^= 1;
}
}
}
}
}
(void) gb;
return;
}

void gb_set_rtc(struct gb_s *gb, const struct tm * const time)
{
gb->cart_rtc[0] = time->tm_sec;
gb->cart_rtc[1] = time->tm_min;
gb->cart_rtc[2] = time->tm_hour;
gb->cart_rtc[3] = time->tm_yday & 0xFF; /* Low 8 bits of day counter. */
gb->cart_rtc[4] = time->tm_yday >> 8; /* High 1 bit of day counter. */
gb->rtc_real.bytes[0] = time->tm_sec;
gb->rtc_real.bytes[1] = time->tm_min;
gb->rtc_real.bytes[2] = time->tm_hour;
gb->rtc_real.bytes[3] = time->tm_yday & 0xFF; /* Low 8 bits of day counter. */
gb->rtc_real.bytes[4] = time->tm_yday >> 8; /* High 1 bit of day counter. */
}
#endif // PEANUT_GB_HEADER_ONLY

Expand Down Expand Up @@ -3847,10 +3886,8 @@ uint8_t gb_colour_hash(struct gb_s *gb);
const char* gb_get_rom_name(struct gb_s* gb, char *title_str);

/**
* Tick the internal RTC by one second. This does not affect games with no RTC
* support.
*
* \param gb An initialised emulator context. Must not be NULL.
* Deprecated. Will be removed in the next major version.
* RTC is ticked internally and this function has no effect.
*/
void gb_tick_rtc(struct gb_s *gb);

Expand Down

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