65 lines
1.2 KiB
C
65 lines
1.2 KiB
C
#include <dma.h>
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#include <ppu.h>
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#include <bus.h>
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#include <cart.h>
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#include <ppu.h>
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#include <ram.h>
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static dma_context ctx;
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void dma_start(u8 start) {
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ctx.start_delay = 1;
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ctx.value_buffer = start;
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ctx.dma_waiting = true;
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}
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void dma_begin() {
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ctx.active = true;
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ctx.byte = 0;
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ctx.value = ctx.value_buffer;
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ctx.dma_waiting = false;
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}
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void dma_tick() {
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ctx.transferring = false;
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if (ctx.start_delay) {
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ctx.start_delay--;
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} else if(ctx.dma_waiting) {
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dma_begin();
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}
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if (!ctx.active) {
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return;
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}
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ctx.transferring = true;
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u8 data = 0;
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u16 addr = (ctx.value << 8) | ctx.byte;
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if(ctx.value < 0x80) {
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data = cart_read(addr);
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} else if (ctx.value < 0xA0) {
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data = ppu_vram_read(addr);
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} else if (ctx.value < 0xC0) {
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data = cart_read(addr);
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} else {
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data = wram_read((addr & 0x1FFF) | 0xC000);
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}
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ppu_oam_write(ctx.byte, data);
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ctx.byte++;
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ctx.active = ctx.byte < 0xA0;
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}
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bool dma_transferring() {
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return ctx.transferring;// && ctx.active;
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}
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void dma_save_state(dma_state* state) {
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state->ctx = ctx;
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}
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void dma_load_state(const dma_state* state) {
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ctx = state->ctx;
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} |