118 lines
4.2 KiB
Rust
118 lines
4.2 KiB
Rust
use super::{
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NativeBus, PPU_DOTS_PER_FRAME, PPU_DOTS_PER_SCANLINE, PPU_PRERENDER_SCANLINE,
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PPU_VBLANK_START_SCANLINE,
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};
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use crate::native_core::cpu::CpuBus;
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use crate::native_core::mapper::Mapper;
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impl NativeBus {
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fn clock_one_cpu_cycle(&mut self) {
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self.cpu_cycles_since_poll = self.cpu_cycles_since_poll.saturating_add(1);
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for _ in 0..3 {
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self.clock_ppu_dot();
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}
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self.mapper.clock_cpu(1);
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self.apu.clock_cpu_cycle();
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}
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fn service_dmc_dma(&mut self, addr: u16) {
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let byte = self.dma_read(addr);
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self.apu.provide_dmc_dma_byte(byte);
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// DMC DMA steals CPU bus cycles while APU/PPU/mapper keep ticking.
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for _ in 0..4 {
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self.clock_one_cpu_cycle();
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}
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}
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pub(super) fn dma_read(&mut self, addr: u16) -> u8 {
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<Self as CpuBus>::read(self, addr)
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}
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pub(super) fn clock_ppu_dot(&mut self) {
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self.ppu_dot += 1;
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if self.ppu_dot >= PPU_DOTS_PER_FRAME {
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self.ppu_dot = 0;
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self.frame_complete = true;
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self.odd_frame = !self.odd_frame;
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}
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let scanline = self.ppu_dot / PPU_DOTS_PER_SCANLINE;
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let dot = self.ppu_dot % PPU_DOTS_PER_SCANLINE;
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let rendering_enabled = self.ppu.rendering_enabled();
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{
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let mapper: &(dyn Mapper + Send) = &*self.mapper;
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self.ppu.render_dot(mapper, scanline, dot);
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}
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if rendering_enabled && (scanline < 240 || scanline == PPU_PRERENDER_SCANLINE) {
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if self.mapper.needs_ppu_a12_clock() {
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let a12_high = self.ppu.mmc3_a12_high_at(scanline, dot);
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if a12_high {
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if !self.mmc3_a12_prev_high
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&& self.mmc3_a12_low_dots >= 8
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&& self.mmc3_last_irq_scanline != scanline
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{
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self.mapper.clock_scanline();
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self.mmc3_last_irq_scanline = scanline;
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}
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self.mmc3_a12_prev_high = true;
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self.mmc3_a12_low_dots = 0;
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} else {
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self.mmc3_a12_prev_high = false;
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self.mmc3_a12_low_dots = self.mmc3_a12_low_dots.saturating_add(1);
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}
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} else if dot == 260 {
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self.mapper.clock_scanline();
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}
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} else {
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self.mmc3_a12_prev_high = false;
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self.mmc3_a12_low_dots = self.mmc3_a12_low_dots.saturating_add(1);
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}
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if rendering_enabled && scanline == PPU_PRERENDER_SCANLINE && dot == 339 && self.odd_frame {
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// NTSC odd frame timing: skip pre-render dot 340 when rendering is enabled.
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self.ppu_dot = self.ppu_dot.saturating_add(1);
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}
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if !self.in_vblank && scanline == PPU_VBLANK_START_SCANLINE && dot == 1 {
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if self.suppress_vblank_this_frame {
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self.suppress_vblank_this_frame = false;
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self.in_vblank = false;
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self.ppu.set_vblank(false);
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} else {
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self.in_vblank = true;
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self.ppu.set_vblank(true);
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if self.ppu.nmi_enabled() {
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self.nmi_pending = true;
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}
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}
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} else if scanline == PPU_PRERENDER_SCANLINE && dot == 1 {
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self.in_vblank = false;
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self.ppu.set_vblank(false);
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self.ppu.set_sprite0_hit(false);
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self.ppu.set_sprite_overflow(false);
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self.suppress_vblank_this_frame = false;
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}
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}
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pub(super) fn clock_cpu_cycles(&mut self, cycles: u32) {
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if cycles == 0 {
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return;
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}
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let mut remaining = cycles;
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while remaining != 0 {
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self.clock_one_cpu_cycle();
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while let Some(addr) = self.apu.take_dmc_dma_request() {
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self.service_dmc_dma(addr);
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}
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remaining -= 1;
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}
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}
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pub(super) fn note_scroll_write_now(&mut self) {
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let scanline = (self.ppu_dot / PPU_DOTS_PER_SCANLINE) as usize;
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let dot = self.ppu_dot % PPU_DOTS_PER_SCANLINE;
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self.ppu.note_scroll_register_write(scanline, dot);
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}
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}
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