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More accurate emulation of the OAM bug

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This commit is contained in:
Lior Halphon 2018-03-24 14:46:51 +03:00
parent 5cb74fb684
commit 9093f22293
1 changed files with 12 additions and 3 deletions
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15
Core/z80_cpu.c
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@ -23,15 +23,24 @@ typedef void GB_opcode_t(GB_gameboy_t *gb, uint8_t opcode);
*/
static uint8_t bitwise_glitch(uint8_t a, uint8_t b, uint8_t c)
{
return ((a ^ c) & (b ^ c)) ^ c;
}
static void trigger_oam_bug(GB_gameboy_t *gb, uint8_t register_id)
{
if (gb->is_cgb) return;
if (gb->registers[register_id] >= 0xFE00 && gb->registers[register_id] < 0xFF00) {
if (gb->oam_search_index < 38 && gb->oam_search_index > 0) {
/* Todo: bytes 2-7 are copied from the previous 8 bytes, but bytes 0 and 1 behave differently
on real hardware*/
for (unsigned i = 0; i < 8; i++) {
gb->oam[gb->oam_search_index * 4 + 4] = bitwise_glitch(gb->oam[gb->oam_search_index * 4 + 4],
gb->oam[gb->oam_search_index * 4 - 4],
gb->oam[gb->oam_search_index * 4]);
gb->oam[gb->oam_search_index * 4 + 5] = bitwise_glitch(gb->oam[gb->oam_search_index * 4 + 5],
gb->oam[gb->oam_search_index * 4 - 3],
gb->oam[gb->oam_search_index * 4 + 1]);
for (unsigned i = 2; i < 8; i++) {
gb->oam[gb->oam_search_index * 4 + 4 + i] = gb->oam[gb->oam_search_index * 4 - 4 + i];
}
}