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A test ROM I wrote seems to contradicts some of AntonioND’s findings regrading PPU timing in CGB mode. CGB mode now behaves like DMG mode until I figure out what caused the difference.

This commit is contained in:
Lior Halphon 2017-09-02 23:51:02 +03:00
parent 9b490396bb
commit 0532d2a159
1 changed files with 8 additions and 2 deletions
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10
Core/display.c
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@ -289,7 +289,10 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
} }
uint8_t atomic_increase = gb->cgb_double_speed? 2 : 4; uint8_t atomic_increase = gb->cgb_double_speed? 2 : 4;
uint8_t stat_delay = gb->cgb_double_speed? 2 : (gb->cgb_mode? 0 : 4); /* According to AntonioND's docs this value should be 0 in CGB mode, but tests I ran on my CGB seem to contradict
these findings.
Todo: Investigate what causes the difference between our findings */
uint8_t stat_delay = gb->cgb_double_speed? 2 : 4; //(gb->cgb_mode? 0 : 4);
/* Todo: This is correct for DMG. Is it correct for the 3 CGB modes (DMG/single/double)?*/ /* Todo: This is correct for DMG. Is it correct for the 3 CGB modes (DMG/single/double)?*/
uint8_t scx_delay = ((gb->effective_scx & 7) + atomic_increase - 1) & ~(atomic_increase - 1); uint8_t scx_delay = ((gb->effective_scx & 7) + atomic_increase - 1) & ~(atomic_increase - 1);
/* Todo: These are correct for DMG, DMG-mode CGB, and single speed CGB. Is is correct for double speed CGB? */ /* Todo: These are correct for DMG, DMG-mode CGB, and single speed CGB. Is is correct for double speed CGB? */
@ -558,8 +561,10 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
gb->io_registers[GB_IO_IF] |= 2; gb->io_registers[GB_IO_IF] |= 2;
} }
#if 0
/* The value of LY is glitched in the last cycle of every line in CGB mode CGB in single speed /* The value of LY is glitched in the last cycle of every line in CGB mode CGB in single speed
This is based on GiiBiiAdvance's docs */ This is based on AntonioND's docs, however I could not reproduce these findings on my CGB.
Todo: Find out why my tests contradict these docs */
if (gb->cgb_mode && !gb->cgb_double_speed && if (gb->cgb_mode && !gb->cgb_double_speed &&
gb->display_cycles % LINE_LENGTH == LINE_LENGTH - 4) { gb->display_cycles % LINE_LENGTH == LINE_LENGTH - 4) {
uint8_t glitch_pattern[] = {0, 0, 2, 0, 4, 4, 6, 0, 8}; uint8_t glitch_pattern[] = {0, 0, 2, 0, 4, 4, 6, 0, 8};
@ -570,6 +575,7 @@ static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
gb->io_registers[GB_IO_LY] = glitch_pattern[gb->io_registers[GB_IO_LY] & 7] | (gb->io_registers[GB_IO_LY] & 0xF8); gb->io_registers[GB_IO_LY] = glitch_pattern[gb->io_registers[GB_IO_LY] & 7] | (gb->io_registers[GB_IO_LY] & 0xF8);
} }
} }
#endif
} }
void GB_display_run(GB_gameboy_t *gb, uint8_t cycles) void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)