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H/GDMA was 4 times faster than it should have been. Made it also more accurate. Fixes #56

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This commit is contained in:
Lior Halphon 2018-04-13 14:41:39 +03:00
parent 51e3cb7b9f
commit f1ec42d4ba
3 changed files with 19 additions and 18 deletions
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2
Core/gb.h
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@ -280,7 +280,7 @@ struct GB_gameboy_internal_s {
bool hdma_on;
bool hdma_on_hblank;
uint8_t hdma_steps_left;
uint16_t hdma_cycles; // in 8MHz units
int16_t hdma_cycles; // in 8MHz units
uint16_t hdma_current_src, hdma_current_dest;
uint8_t dma_steps_left;

13
Core/memory.c
View File

@ -767,7 +767,7 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
gb->hdma_on_hblank = (value & 0x80) != 0;
if (gb->hdma_on_hblank && (gb->io_registers[GB_IO_STAT] & 3) == 0) {
gb->hdma_on = true;
gb->hdma_cycles = 0;
gb->hdma_cycles = -8;
}
gb->io_registers[GB_IO_HDMA5] = value;
gb->hdma_steps_left = (gb->io_registers[GB_IO_HDMA5] & 0x7F) + 1;
@ -775,7 +775,7 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
if (gb->hdma_current_dest + (gb->hdma_steps_left << 4) > 0xFFFF) {
gb->hdma_steps_left = (0x10000 - gb->hdma_current_dest) >> 4;
}
gb->hdma_cycles = 0;
gb->hdma_cycles = -8;
return;
/* Todo: what happens when starting a transfer during a transfer?
@ -863,6 +863,7 @@ void GB_dma_run(GB_gameboy_t *gb)
/* Todo: measure this value */
gb->dma_cycles -= 4;
gb->dma_steps_left--;
if (gb->dma_current_src < 0xe000) {
gb->oam[gb->dma_current_dest++] = GB_read_memory(gb, gb->dma_current_src);
}
@ -882,13 +883,12 @@ void GB_dma_run(GB_gameboy_t *gb)
void GB_hdma_run(GB_gameboy_t *gb)
{
if (!gb->hdma_on) return;
while (gb->hdma_cycles >= 0x10) {
gb->hdma_cycles -= 0x10;
while (gb->hdma_cycles >= 0x4) {
gb->hdma_cycles -= 0x4;
for (uint8_t i = 0; i < 0x10; i++) {
GB_write_memory(gb, 0x8000 | (gb->hdma_current_dest++ & 0x1FFF), GB_read_memory(gb, (gb->hdma_current_src++)));
}
if ((gb->hdma_current_dest & 0xf) == 0) {
if(--gb->hdma_steps_left == 0){
gb->hdma_on = false;
gb->hdma_on_hblank = false;
@ -901,3 +901,4 @@ void GB_hdma_run(GB_gameboy_t *gb)
}
}
}
}

2
Core/z80_cpu.c
View File

@ -1438,6 +1438,6 @@ void GB_cpu_run(GB_gameboy_t *gb)
if (gb->hdma_starting) {
gb->hdma_starting = false;
gb->hdma_on = true;
gb->hdma_cycles = 0;
gb->hdma_cycles = -8;
}
}