595 lines
22 KiB
C#
595 lines
22 KiB
C#
//http://nesdev.parodius.com/bbs/viewtopic.php?p=4571&sid=db4c7e35316cc5d734606dd02f11dccb
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//todo - read http://wiki.nesdev.com/w/index.php/PPU_sprite_priority
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//TODO - correctly emulate PPU OFF state
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using BizHawk.Common;
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using System;
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namespace BizHawk.Emulation.Cores.Nintendo.NES
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{
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sealed partial class PPU
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{
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const int kFetchTime = 2;
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struct BGDataRecord {
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public byte nt, at;
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public byte pt_0, pt_1;
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};
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public short[] xbuf = new short[256*240];
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// values here are used in sprite evaluation
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public bool sprite_eval_write;
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public byte read_value;
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public int soam_index;
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public int soam_index_prev;
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public int soam_m_index;
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public int oam_index;
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public int read_value_aux;
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public int soam_m_index_aux;
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public int oam_index_aux;
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public bool is_even_cycle;
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public bool sprite_zero_in_range=false;
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public bool sprite_zero_go = false;
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public int yp;
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public int spriteHeight;
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public int o_bug; // this is incramented when checks for sprite overflow start, mirroring a hardware bug
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public byte[] soam = new byte[512]; // in a real nes, this would only be 32, but we wish to allow more then 8 sprites per scanline
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struct TempOAM
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{
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public byte oam_y;
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public byte oam_ind;
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public byte oam_attr;
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public byte oam_x;
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public byte patterns_0;
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public byte patterns_1;
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}
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TempOAM[] t_oam = new TempOAM[64];
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int ppu_addr_temp;
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void Read_bgdata(ref BGDataRecord bgdata)
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{
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for (int i = 0; i < 8; i++)
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Read_bgdata(i,ref bgdata);
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}
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void Read_bgdata(int cycle, ref BGDataRecord bgdata)
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{
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switch (cycle)
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{
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case 0:
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ppu_addr_temp = ppur.get_ntread();
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bgdata.nt = ppubus_read(ppu_addr_temp, true);
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runppu(1);
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break;
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case 1:
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runppu(1);
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break;
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case 2:
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{
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ppu_addr_temp = ppur.get_atread();
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byte at = ppubus_read(ppu_addr_temp, true);
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//modify at to get appropriate palette shift
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if ((ppur.vt & 2) != 0) at >>= 4;
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if ((ppur.ht & 2) != 0) at >>= 2;
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at &= 0x03;
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at <<= 2;
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bgdata.at = at;
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//horizontal scroll clocked at cycle 3 and then
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//vertical scroll at 251
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runppu(1);
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if (reg_2001.PPUON)
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{
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ppur.increment_hsc();
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if (ppur.status.cycle == 251)
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ppur.increment_vs();
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}
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break;
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}
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case 3:
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runppu(1);
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break;
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case 4:
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ppu_addr_temp = ppur.get_ptread(bgdata.nt);
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bgdata.pt_0 = ppubus_read(ppu_addr_temp, true);
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runppu(1);
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break;
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case 5:
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runppu(1);
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break;
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case 6:
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ppu_addr_temp |= 8;
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bgdata.pt_1 = ppubus_read(ppu_addr_temp, true);
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runppu(1);
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break;
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case 7:
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runppu(1);
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break;
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} //switch(cycle)
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}
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//TODO - check flashing sirens in werewolf
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short PaletteAdjustPixel(int pixel)
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{
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//tack on the deemph bits. THESE MAY BE ORDERED WRONG. PLEASE CHECK IN THE PALETTE CODE
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return (short)(pixel | reg_2001.intensity_lsl_6);
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}
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const int kLineTime = 341;
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public unsafe void FrameAdvance()
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{
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BGDataRecord *bgdata = stackalloc BGDataRecord[34]; //one at the end is junk, it can never be rendered
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//262 scanlines
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if (ppudead != 0)
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{
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FrameAdvance_ppudead();
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return;
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}
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Reg2002_vblank_active_pending = true;
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ppuphase = PPUPHASE.VBL;
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ppur.status.sl = 241;
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//Not sure if this is correct. According to Matt Conte and my own tests, it is. Timing is probably off, though.
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//NOTE: Not having this here breaks a Super Donkey Kong game.
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if (reg_2001.show_obj || reg_2001.show_bg) reg_2003 = 0;
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//this was repeatedly finetuned from the fceux days thrugh the old cpu core and into the new one to pass 05-nmi_timing.nes
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//note that there is still some leniency. for instance, 4,2 will pass in addition to 3,3
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const int delay = 6;
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runppu(3);
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bool nmi_destiny = reg_2000.vblank_nmi_gen && Reg2002_vblank_active;
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runppu(3);
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if (nmi_destiny) TriggerNMI();
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nes.Board.AtVsyncNMI();
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runppu(postNMIlines * kLineTime - delay);
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//this seems to run just before the dummy scanline begins
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clear_2002();
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idleSynch ^= true;
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//render 241 scanlines (including 1 dummy at beginning)
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for (int sl = 0; sl < 241; sl++)
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{
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ppur.status.cycle = 0;
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ppur.status.sl = sl;
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soam_index = 0;
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soam_m_index = 0;
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soam_m_index_aux = 0;
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oam_index_aux = 0;
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oam_index = 0;
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o_bug = 0;
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is_even_cycle = true;
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sprite_eval_write = true;
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sprite_zero_go = false;
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if (sprite_zero_in_range)
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sprite_zero_go = true;
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sprite_zero_in_range = false;
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yp = sl - 1;
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ppuphase = PPUPHASE.BG;
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if (NTViewCallback != null && yp == NTViewCallback.Scanline) NTViewCallback.Callback();
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if (PPUViewCallback != null && yp == PPUViewCallback.Scanline) PPUViewCallback.Callback();
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//ok, we're also going to draw here.
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//unless we're on the first dummy scanline
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if (sl != 0)
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{
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//the main scanline rendering loop:
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//32 times, we will fetch a tile and then render 8 pixels.
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//two of those tiles were read in the last scanline.
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int yp_shift = yp << 8;
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for (int xt = 0; xt < 32; xt++)
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{
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int xstart = xt << 3;
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int target = yp_shift + xstart;
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int rasterpos = xstart;
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spriteHeight = reg_2000.obj_size_16 ? 16 : 8;
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//check all the conditions that can cause things to render in these 8px
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bool renderspritenow = reg_2001.show_obj && (xt > 0 || reg_2001.show_obj_leftmost);
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bool renderbgnow = reg_2001.show_bg && (xt > 0 || reg_2001.show_bg_leftmost);
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for (int xp = 0; xp < 8; xp++, rasterpos++)
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{
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//////////////////////////////////////////////////
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//Sprite Evaluation Start
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//////////////////////////////////////////////////
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if (ppur.status.cycle <= 63 && !is_even_cycle)
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{
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// the first 64 cycles of each scanline are used to initialize sceondary OAM
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// the actual effect setting a flag that always returns 0xFF from a OAM read
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// this is a bit of a shortcut to save some instructions
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// data is read from OAM as normal but never used
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soam[soam_index] = 0xFF;
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soam_index++;
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}
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if (ppur.status.cycle == 64)
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soam_index = 0;
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// otherwise, scan through OAM and test if sprites are in range
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// if they are, they get copied to the secondary OAM
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if (ppur.status.cycle >= 64)
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{
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if (oam_index==64)
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{
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oam_index_aux = 0;
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oam_index = 0;
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sprite_eval_write = false;
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}
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if (is_even_cycle)
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{
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read_value = OAM[oam_index * 4+soam_m_index];
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if (oam_index_aux>63)
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oam_index_aux = 63;
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read_value_aux = OAM[oam_index_aux * 4 + soam_m_index_aux];
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}
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else if (sprite_eval_write)
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{
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if (soam_index >= 8)
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{
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// this code mirrors sprite overflow bug behaviour
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// see http://wiki.nesdev.com/w/index.php/PPU_sprite_evaluation
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if (yp >= read_value && yp < read_value + spriteHeight && reg_2001.PPUON)
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{
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Reg2002_objoverflow = true;
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}
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else
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{
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soam_m_index++;
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oam_index++;
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if (soam_m_index == 4)
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soam_m_index = 0;
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}
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}
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//look for sprites
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soam[soam_index * 4] = OAM[oam_index_aux * 4];
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if (yp >= read_value_aux && yp < read_value_aux + spriteHeight && soam_m_index_aux == 0)
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{
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//a flag gets set if sprite zero is in range
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if (oam_index_aux == 0)
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sprite_zero_in_range = true;
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soam_m_index_aux++;
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} else if (soam_m_index_aux > 0 && soam_m_index_aux < 4)
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{
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soam[soam_index * 4 + soam_m_index_aux] = OAM[oam_index_aux * 4 + soam_m_index_aux];
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soam_m_index_aux++;
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if (soam_m_index_aux == 4)
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{
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oam_index_aux++;
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soam_index++;
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soam_m_index_aux = 0;
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}
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} else
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{
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oam_index_aux++;
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}
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if (soam_index<8)
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{
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soam_m_index = soam_m_index_aux;
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oam_index = oam_index_aux;
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}
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}
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}
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//////////////////////////////////////////////////
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//Sprite Evaluation End
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//////////////////////////////////////////////////
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//process the current clock's worth of bg data fetching
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//this needs to be split into 8 pieces or else exact sprite 0 hitting wont work due to the cpu not running while the sprite renders below
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Read_bgdata(xp, ref bgdata[xt + 2]);
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//bg pos is different from raster pos due to its offsetability.
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//so adjust for that here
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int bgpos = rasterpos + ppur.fh;
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int bgpx = bgpos & 7;
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int bgtile = bgpos >> 3;
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int pixel = 0, pixelcolor = PALRAM[pixel];
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//according to qeed's doc, use palette 0 or $2006's value if it is & 0x3Fxx
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//at one point I commented this out to fix bottom-left garbage in DW4. but it's needed for full_nes_palette.
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//solution is to only run when PPU is actually OFF (left-suppression doesnt count)
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if (!reg_2001.show_bg && !reg_2001.show_obj)
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{
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// if there's anything wrong with how we're doing this, someone please chime in
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int addr = ppur.get_2007access();
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if ((addr & 0x3F00) == 0x3F00)
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{
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pixel = addr & 0x1F;
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}
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pixelcolor = PALRAM[pixel];
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pixelcolor |= 0x8000; //whats this? i think its a flag to indicate a hidden background to be used by the canvas filling logic later
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}
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//generate the BG data
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if (renderbgnow)
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{
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byte pt_0 = bgdata[bgtile].pt_0;
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byte pt_1 = bgdata[bgtile].pt_1;
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int sel = 7 - bgpx;
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pixel = ((pt_0 >> sel) & 1) | (((pt_1 >> sel) & 1) << 1);
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if (pixel != 0)
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pixel |= bgdata[bgtile].at;
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pixelcolor = PALRAM[pixel];
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}
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if (!nes.Settings.DispBackground)
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pixelcolor = 0x8000; //whats this? i think its a flag to indicate a hidden background to be used by the canvas filling logic later
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//look for a sprite to be drawn
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bool havepixel = false;
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for (int s = 0; s < soam_index_prev; s++)
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{
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int x = t_oam[s].oam_x;
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if (rasterpos >= x && rasterpos < x + 8)
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{
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//build the pixel.
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//fetch the LSB of the patterns
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int spixel = t_oam[s].patterns_0 & 1;
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spixel |= (t_oam[s].patterns_1 & 1) << 1;
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//shift down the patterns so the next pixel is in the LSB
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t_oam[s].patterns_0 >>= 1;
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t_oam[s].patterns_1 >>= 1;
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//bail out if we already have a pixel from a higher priority sprite.
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//notice that we continue looping anyway, so that we can shift down the patterns
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//transparent pixel bailout
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if (!renderspritenow || havepixel || spixel == 0) continue;
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havepixel = true;
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//TODO - make sure we dont trigger spritehit if the edges are masked for either BG or OBJ
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//spritehit:
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//1. is it sprite#0?
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//2. is the bg pixel nonzero?
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//then, it is spritehit.
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Reg2002_objhit |= (sprite_zero_go && s==0 && pixel != 0 && rasterpos < 255 && reg_2001.show_bg && reg_2001.show_obj);
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//priority handling, if in front of BG:
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bool drawsprite = !(((t_oam[s].oam_attr & 0x20) != 0) && ((pixel & 3) != 0));
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if (drawsprite && nes.Settings.DispSprites)
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{
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//bring in the palette bits and palettize
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spixel |= (t_oam[s].oam_attr & 3) << 2;
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//save it for use in the framebuffer
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pixelcolor = PALRAM[0x10 + spixel];
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}
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} //rasterpos in sprite range
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} //oamcount loop
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if (reg_2001.color_disable)
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pixelcolor &= 0x30;
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xbuf[target] = PaletteAdjustPixel(pixelcolor);
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target++;
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} //loop across 8 pixels
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} //loop across 32 tiles
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}
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else
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for (int xt = 0; xt < 32; xt++)
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Read_bgdata(ref bgdata[xt + 2]);
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// normally only 8 sprites are allowed, but with a particular setting we can have more then that
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soam_index_prev = soam_index;
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if (soam_index_prev > 8 && !nes.Settings.AllowMoreThanEightSprites)
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soam_index_prev = 8;
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ppuphase = PPUPHASE.OBJ;
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spriteHeight = reg_2000.obj_size_16 ? 16 : 8;
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// if there are less then 8 evaluated sprites, we still process 8 sprites
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int bound;
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if (soam_index_prev>8)
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{
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bound = soam_index_prev;
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} else
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{
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bound = 8;
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}
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for (int s = 0; s < bound; s++)
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{
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//if this is a real sprite sprite, then it is not above the 8 sprite limit.
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//this is how we support the no 8 sprite limit feature.
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//not that at some point we may need a virtual CALL_PPUREAD which just peeks and doesnt increment any counters
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//this could be handy for the debugging tools also
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bool realSprite = (s < 8);
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bool junksprite = (!reg_2001.PPUON);
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bool extra_sprite = (s >= 8);
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t_oam[s].oam_y = soam[s*4];
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t_oam[s].oam_ind = soam[s * 4+1];
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t_oam[s].oam_attr = soam[s * 4+2];
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t_oam[s].oam_x = soam[s * 4+3];
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int line = yp - t_oam[s].oam_y;
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if ((t_oam[s].oam_attr & 0x80) != 0) //vflip
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line = spriteHeight - line - 1;
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int patternNumber = t_oam[s].oam_ind;
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int patternAddress;
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//8x16 sprite handling:
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if (reg_2000.obj_size_16)
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{
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int bank = (patternNumber & 1) << 12;
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patternNumber = patternNumber & ~1;
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patternNumber |= (line >> 3) & 1;
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patternAddress = (patternNumber << 4) | bank;
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}
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else
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patternAddress = (patternNumber << 4) | (reg_2000.obj_pattern_hi << 12);
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//offset into the pattern for the current line.
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//tricky: tall sprites have already had lines>8 taken care of by getting a new pattern number above.
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//so we just need the line offset for the second pattern
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patternAddress += line & 7;
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//garbage nametable fetches + scroll resets
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int garbage_todo = 2;
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ppubus_read(ppur.get_ntread(), true);
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if (reg_2001.PPUON)
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{
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if (sl == 0 && ppur.status.cycle == 304)
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{
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runppu(1);
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read_value = t_oam[s].oam_y;
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if (reg_2001.PPUON) ppur.install_latches();
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runppu(1);
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read_value = t_oam[s].oam_ind;
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garbage_todo = 0;
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}
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if ((sl != 0) && ppur.status.cycle == 256)
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{
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runppu(1);
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read_value = t_oam[s].oam_y;
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//at 257: 3d world runner is ugly if we do this at 256
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if (reg_2001.PPUON) ppur.install_h_latches();
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runppu(1);
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read_value = t_oam[s].oam_ind;
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garbage_todo = 0;
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}
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}
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if (realSprite)
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{
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for (int i=0;i<garbage_todo;i++)
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{
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runppu(1);
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if (i==0)
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{
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read_value = t_oam[s].oam_y;
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} else
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{
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read_value = t_oam[s].oam_ind;
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}
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}
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}
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ppubus_read(ppur.get_atread(), true); //at or nt?
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if (realSprite)
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{
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runppu(1);
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read_value = t_oam[s].oam_attr;
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runppu(1);
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read_value = t_oam[s].oam_x;
|
|
}
|
|
|
|
// TODO - fake sprites should not come through ppubus_read but rather peek it
|
|
// (at least, they should not probe it with AddressPPU. maybe the difference between peek and read is not necessary)
|
|
if (junksprite)
|
|
{
|
|
if (realSprite)
|
|
{
|
|
ppubus_read(patternAddress, true);
|
|
ppubus_read(patternAddress, true);
|
|
runppu(kFetchTime * 2);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
int addr = patternAddress;
|
|
t_oam[s].patterns_0 = ppubus_read(addr, true);
|
|
if (realSprite)
|
|
{
|
|
runppu(kFetchTime);
|
|
read_value = t_oam[s].oam_x;
|
|
}
|
|
addr += 8;
|
|
t_oam[s].patterns_1 = ppubus_read(addr, true);
|
|
if (realSprite)
|
|
{
|
|
runppu(kFetchTime);
|
|
read_value = t_oam[s].oam_x;
|
|
}
|
|
|
|
|
|
// hflip
|
|
if ((t_oam[s].oam_attr & 0x40) == 0)
|
|
{
|
|
t_oam[s].patterns_0 = BitReverse.Byte8[t_oam[s].patterns_0];
|
|
t_oam[s].patterns_1 = BitReverse.Byte8[t_oam[s].patterns_1];
|
|
}
|
|
|
|
}
|
|
|
|
} // sprite pattern fetch loop
|
|
|
|
ppuphase = PPUPHASE.BG;
|
|
|
|
// fetch BG: two tiles for next line
|
|
for (int xt = 0; xt < 2; xt++)
|
|
{
|
|
Read_bgdata(ref bgdata[xt]);
|
|
}
|
|
|
|
|
|
// this sequence is tuned to pass 10-even_odd_timing.nes
|
|
runppu(kFetchTime);
|
|
bool evenOddDestiny = (reg_2001.show_bg|| reg_2001.show_obj);
|
|
runppu(kFetchTime);
|
|
|
|
// After memory access 170, the PPU simply rests for 4 cycles (or the
|
|
// equivelant of half a memory access cycle) before repeating the whole
|
|
// pixel/scanline rendering process. If the scanline being rendered is the very
|
|
// first one on every second frame, then this delay simply doesn't exist.
|
|
if (sl == 0 && idleSynch && evenOddDestiny && chopdot)
|
|
{ }
|
|
else
|
|
runppu(1);
|
|
} // scanline loop
|
|
|
|
ppur.status.sl = 241;
|
|
|
|
//idle for pre NMI lines
|
|
runppu(preNMIlines * kLineTime);
|
|
|
|
} //FrameAdvance
|
|
|
|
|
|
void FrameAdvance_ppudead()
|
|
{
|
|
//not quite emulating all the NES power up behavior
|
|
//since it is known that the NES ignores writes to some
|
|
//register before around a full frame, but no games
|
|
//should write to those regs during that time, it needs
|
|
//to wait for vblank
|
|
ppur.status.sl = 241;
|
|
runppu(postNMIlines * kLineTime);
|
|
ppur.status.sl = 0;
|
|
Reg2002_vblank_active = true;
|
|
runppu(241 * kLineTime);
|
|
runppu(preNMIlines * kLineTime);
|
|
--ppudead;
|
|
}
|
|
}
|
|
}
|
|
|