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180 lines
2.9 KiB
180 lines
2.9 KiB
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#include <stdlib.h>
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#include "defs.h"
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#include "hw.h"
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#include "cpu.h"
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#include "regs.h"
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#include "lcd.h"
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#define C (cpu.lcdc)
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/*
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* stat_trigger updates the STAT interrupt line to reflect whether any
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* of the conditions set to be tested (by bits 3-6 of R_STAT) are met.
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* This function should be called whenever any of the following occur:
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* 1) LY or LYC changes.
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* 2) A state transition affects the low 2 bits of R_STAT (see below).
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* 3) The program writes to the upper bits of R_STAT.
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* stat_trigger also updates bit 2 of R_STAT to reflect whether LY=LYC.
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*/
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void stat_trigger()
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{
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static const int condbits[4] = { 0x08, 0x30, 0x20, 0x00 };
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int flag = 0;
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if ((R_LY < 0x91) && (R_LY == R_LYC))
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{
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R_STAT |= 0x04;
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if (R_STAT & 0x40) flag = IF_STAT;
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}
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else R_STAT &= ~0x04;
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if (R_STAT & condbits[R_STAT&3]) flag = IF_STAT;
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if (!(R_LCDC & 0x80)) flag = 0;
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hw_interrupt(flag, IF_STAT);
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}
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void stat_write(byte b)
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{
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R_STAT = (R_STAT & 0x07) | (b & 0x78);
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if (!hw.cgb && !(R_STAT & 2)) /* DMG STAT write bug => interrupt */
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hw_interrupt(IF_STAT, IF_STAT);
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stat_trigger();
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}
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/*
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* stat_change is called when a transition results in a change to the
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* LCD STAT condition (the low 2 bits of R_STAT). It raises or lowers
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* the VBLANK interrupt line appropriately and calls stat_trigger to
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* update the STAT interrupt line.
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*/
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static void stat_change(int stat)
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{
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stat &= 3;
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R_STAT = (R_STAT & 0x7C) | stat;
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if (stat != 1) hw_interrupt(0, IF_VBLANK);
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/* hw_interrupt((stat == 1) ? IF_VBLANK : 0, IF_VBLANK); */
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stat_trigger();
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}
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void lcdc_change(byte b)
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{
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byte old = R_LCDC;
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R_LCDC = b;
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if ((R_LCDC ^ old) & 0x80) /* lcd on/off change */
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{
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R_LY = 0;
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stat_change(2);
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C = 40;
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lcd_begin();
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}
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}
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void lcdc_trans()
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{
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if (!(R_LCDC & 0x80))
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{
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while (C <= 0)
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{
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switch ((byte)(R_STAT & 3))
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{
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case 0:
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case 1:
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stat_change(2);
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C += 40;
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break;
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case 2:
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stat_change(3);
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C += 86;
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break;
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case 3:
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stat_change(0);
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if (hw.hdma & 0x80)
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hw_hdma();
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else
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C += 102;
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break;
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}
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return;
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}
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}
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while (C <= 0)
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{
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switch ((byte)(R_STAT & 3))
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{
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case 1:
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if (!(hw.ilines & IF_VBLANK))
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{
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C += 218;
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hw_interrupt(IF_VBLANK, IF_VBLANK);
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break;
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}
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if (R_LY == 0)
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{
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lcd_begin();
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stat_change(2);
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C += 40;
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break;
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}
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else if (R_LY < 152)
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C += 228;
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else if (R_LY == 152)
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C += 28;
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else
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{
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R_LY = -1;
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C += 200;
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}
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R_LY++;
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stat_trigger();
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break;
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case 2:
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lcd_refreshline();
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stat_change(3);
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C += 86;
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break;
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case 3:
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stat_change(0);
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if (hw.hdma & 0x80)
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hw_hdma();
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/* FIXME -- how much of the hblank does hdma use?? */
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/* else */
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C += 102;
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break;
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case 0:
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if (++R_LY >= 144)
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{
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if (cpu.halt)
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{
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hw_interrupt(IF_VBLANK, IF_VBLANK);
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C += 228;
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}
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else C += 10;
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stat_change(1);
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break;
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}
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stat_change(2);
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C += 40;
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break;
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}
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}
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}
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