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Basic emulation of the OAM bug

This commit is contained in:
Lior Halphon 2018-03-24 00:32:19 +03:00
parent f8c6b9e7a0
commit d343152fca
1 changed files with 35 additions and 12 deletions
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47
Core/z80_cpu.c
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@ -23,6 +23,21 @@ typedef void GB_opcode_t(GB_gameboy_t *gb, uint8_t opcode);
*/
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 + i] = gb->oam[gb->oam_search_index * 4 - 4 + i];
}
}
}
}
static void ill(GB_gameboy_t *gb, uint8_t opcode)
{
GB_log(gb, "Illegal Opcode. Halting.\n");
@ -89,9 +104,10 @@ static void ld_drr_a(GB_gameboy_t *gb, uint8_t opcode)
static void inc_rr(GB_gameboy_t *gb, uint8_t opcode)
{
uint8_t register_id;
GB_advance_cycles(gb, 8);
register_id = (opcode >> 4) + 1;
uint8_t register_id = (opcode >> 4) + 1;
GB_advance_cycles(gb, 4);
trigger_oam_bug(gb, register_id); /* Todo: test T-cycle timing */
GB_advance_cycles(gb, 4);
gb->registers[register_id]++;
}
@ -213,9 +229,10 @@ static void ld_a_drr(GB_gameboy_t *gb, uint8_t opcode)
static void dec_rr(GB_gameboy_t *gb, uint8_t opcode)
{
uint8_t register_id;
GB_advance_cycles(gb, 8);
register_id = (opcode >> 4) + 1;
uint8_t register_id = (opcode >> 4) + 1;
GB_advance_cycles(gb, 4);
trigger_oam_bug(gb, register_id); /* Todo: test T-cycle timing */
GB_advance_cycles(gb, 4);
gb->registers[register_id]--;
}
@ -411,6 +428,7 @@ static void ccf(GB_gameboy_t *gb, uint8_t opcode)
static void ld_dhli_a(GB_gameboy_t *gb, uint8_t opcode)
{
GB_advance_cycles(gb, 3);
trigger_oam_bug(gb, GB_REGISTER_HL); /* Todo: test T-cycle timing */
GB_write_memory(gb, gb->registers[GB_REGISTER_HL]++, gb->registers[GB_REGISTER_AF] >> 8);
GB_advance_cycles(gb, 5);
}
@ -418,6 +436,7 @@ static void ld_dhli_a(GB_gameboy_t *gb, uint8_t opcode)
static void ld_dhld_a(GB_gameboy_t *gb, uint8_t opcode)
{
GB_advance_cycles(gb, 3);
trigger_oam_bug(gb, GB_REGISTER_HL); /* Todo: test T-cycle timing */
GB_write_memory(gb, gb->registers[GB_REGISTER_HL]--, gb->registers[GB_REGISTER_AF] >> 8);
GB_advance_cycles(gb, 5);
}
@ -425,6 +444,7 @@ static void ld_dhld_a(GB_gameboy_t *gb, uint8_t opcode)
static void ld_a_dhli(GB_gameboy_t *gb, uint8_t opcode)
{
GB_advance_cycles(gb, 4);
trigger_oam_bug(gb, GB_REGISTER_HL); /* Todo: test T-cycle timing */
gb->registers[GB_REGISTER_AF] &= 0xFF;
gb->registers[GB_REGISTER_AF] |= GB_read_memory(gb, gb->registers[GB_REGISTER_HL]++) << 8;
GB_advance_cycles(gb, 4);
@ -433,6 +453,7 @@ static void ld_a_dhli(GB_gameboy_t *gb, uint8_t opcode)
static void ld_a_dhld(GB_gameboy_t *gb, uint8_t opcode)
{
GB_advance_cycles(gb, 4);
trigger_oam_bug(gb, GB_REGISTER_HL); /* Todo: test T-cycle timing */
gb->registers[GB_REGISTER_AF] &= 0xFF;
gb->registers[GB_REGISTER_AF] |= GB_read_memory(gb, gb->registers[GB_REGISTER_HL]--) << 8;
GB_advance_cycles(gb, 4);
@ -738,12 +759,13 @@ static void pop_rr(GB_gameboy_t *gb, uint8_t opcode)
uint8_t register_id;
GB_advance_cycles(gb, 4);
register_id = ((opcode >> 4) + 1) & 3;
gb->registers[register_id] = GB_read_memory(gb, gb->registers[GB_REGISTER_SP]);
trigger_oam_bug(gb, GB_REGISTER_SP); /* Todo: test T-cycle timing */
gb->registers[register_id] = GB_read_memory(gb, gb->registers[GB_REGISTER_SP]++);
GB_advance_cycles(gb, 4);
gb->registers[register_id] |= GB_read_memory(gb, gb->registers[GB_REGISTER_SP] + 1) << 8;
trigger_oam_bug(gb, GB_REGISTER_SP); /* Todo: test T-cycle timing */
gb->registers[register_id] |= GB_read_memory(gb, gb->registers[GB_REGISTER_SP]++) << 8;
GB_advance_cycles(gb, 4);
gb->registers[GB_REGISTER_AF] &= 0xFFF0; // Make sure we don't set impossible flags on F! See Blargg's PUSH AF test.
gb->registers[GB_REGISTER_SP] += 2;
}
static void jp_cc_a16(GB_gameboy_t *gb, uint8_t opcode)
@ -801,10 +823,11 @@ static void push_rr(GB_gameboy_t *gb, uint8_t opcode)
uint8_t register_id;
GB_advance_cycles(gb, 7);
register_id = ((opcode >> 4) + 1) & 3;
gb->registers[GB_REGISTER_SP] -= 2;
GB_write_memory(gb, gb->registers[GB_REGISTER_SP] + 1, (gb->registers[register_id]) >> 8);
trigger_oam_bug(gb, GB_REGISTER_SP); /* Todo: test T-cycle timing */
GB_write_memory(gb, --gb->registers[GB_REGISTER_SP], (gb->registers[register_id]) >> 8);
GB_advance_cycles(gb, 4);
GB_write_memory(gb, gb->registers[GB_REGISTER_SP], (gb->registers[register_id]) & 0xFF);
trigger_oam_bug(gb, GB_REGISTER_SP); /* Todo: test T-cycle timing */
GB_write_memory(gb, --gb->registers[GB_REGISTER_SP], (gb->registers[register_id]) & 0xFF);
GB_advance_cycles(gb, 5);
}