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On CGB, the VBlank and STAT interrupts are “delayed” by one T-cycle (relative to IF) since they’re not aligned to a T-Cycle

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Lior Halphon 2017-09-03 00:41:52 +03:00
parent 0532d2a159
commit a1a13c61bf
1 changed files with 11 additions and 1 deletions
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12
Core/display.c
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@ -300,7 +300,7 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
uint8_t vram_blocking_rush = gb->is_cgb? 0 : 4;
for (; cycles; cycles -= atomic_increase) {
gb->delayed_interrupts &= ~3;
gb->display_cycles += atomic_increase;
/* The very first line is 4 clocks shorter when the LCD turns on. Verified on SGB2, CGB in CGB mode and
CGB in double speed mode. */
@ -344,6 +344,10 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
gb->io_registers[GB_IO_STAT] &= ~3;
gb->io_registers[GB_IO_STAT] |= 1;
gb->io_registers[GB_IO_IF] |= 1;
if (gb->is_cgb) {
/* See comment on STAT interrupt at the end of the loop */
gb->delayed_interrupts |= 1;
}
/* Entering VBlank state triggers the OAM interrupt. In CGB, it happens 4 cycles earlier */
if (gb->io_registers[GB_IO_STAT] & 0x20 && !gb->is_cgb) {
@ -559,6 +563,12 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
if (gb->stat_interrupt_line && !previous_stat_interrupt_line) {
gb->io_registers[GB_IO_IF] |= 2;
if (gb->is_cgb) {
/* On CGB, the STAT interrupt is not aligned to a T-Cycle, therefore it is only effective the next T-Cycle
Todo: verify on DMG mode CGB. This was only tested on LYC STAT interrupts, should be tested on others
as well. */
gb->delayed_interrupts |= 2;
}
}
#if 0