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Fixed obscure timer behavior, fixed regression in rapid_toggle.gb.

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This commit is contained in:
Lior Halphon 2017-09-04 18:40:43 +03:00
parent 9bde98dede
commit 72d26c7046
2 changed files with 8 additions and 1 deletions
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3
Core/gb.h
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@ -333,6 +333,9 @@ struct GB_gameboy_internal_s {
uint16_t serial_cycles; /* This field changed its meaning in v0.10 */
uint16_t serial_length;
uint8_t delayed_interrupts; /* When an interrupt occurs while not aligned to a T-cycle, it must be "delayed" */
bool dont_delay_timer_interrupt; /* If the timer glitch causes a TIMA overflow, it causes the timer to overflow
with different timing, so the triggered interrupt is not delayed.
Todo: needs test ROM. */
);
/* APU */

6
Core/timing.c
View File

@ -88,7 +88,9 @@ static void advance_tima_state_machine(GB_gameboy_t *gb)
}
else if (gb->tima_reload_state == GB_TIMA_RELOADING) {
gb->io_registers[GB_IO_IF] |= 4;
gb->delayed_interrupts |= 4; // Timer interrupt is not aligned to a T-cycle and therefore is effective only the next one.
if (!gb->dont_delay_timer_interrupt) {
gb->delayed_interrupts |= 4; // Timer interrupt is not aligned to a T-cycle and therefore is effective only the next one.
}
gb->tima_reload_state = GB_TIMA_RELOADED;
}
}
@ -156,6 +158,7 @@ static void increase_tima(GB_gameboy_t *gb)
{
gb->io_registers[GB_IO_TIMA]++;
if (gb->io_registers[GB_IO_TIMA] == 0) {
gb->dont_delay_timer_interrupt = false;
gb->io_registers[GB_IO_TIMA] = gb->io_registers[GB_IO_TMA];
gb->tima_reload_state = GB_TIMA_RELOADING;
}
@ -195,6 +198,7 @@ void GB_emulate_timer_glitch(GB_gameboy_t *gb, uint8_t old_tac, uint8_t new_tac)
/* And now either the timer must be disabled, or the new bit used for overflow testing be 0. */
if (!(new_tac & 4) || gb->div_cycles & (new_clocks >> 1)) {
increase_tima(gb);
gb->dont_delay_timer_interrupt = true;
}
}
}