Rockboy - gameboy emulation for rockbox, based on gnuboy. Still a bit early, but already playable on iRiver H1xx and the simulators. The archos recorder version is currently rather slow...

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@6104 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 180 insertions, 0 deletions

diff --git a/apps/plugins/rockboy/lcdc.c b/apps/plugins/rockboy/lcdc.c
new file mode 100644
index 0000000..c82b828
--- /dev/null
+++ b/apps/plugins/rockboy/lcdc.c
@@ -0,0 +1,180 @@
+
+
+#include "rockmacros.h"
+
+#include "defs.h"
+#include "hw.h"
+#include "cpu.h"
+#include "regs.h"
+#include "lcd.h"
+
+
+#define C (cpu.lcdc)
+
+
+/*
+ * stat_trigger updates the STAT interrupt line to reflect whether any
+ * of the conditions set to be tested (by bits 3-6 of R_STAT) are met.
+ * This function should be called whenever any of the following occur:
+ * 1) LY or LYC changes.
+ * 2) A state transition affects the low 2 bits of R_STAT (see below).
+ * 3) The program writes to the upper bits of R_STAT.
+ * stat_trigger also updates bit 2 of R_STAT to reflect whether LY=LYC.
+ */
+
+void stat_trigger(void)
+{
+	static const int condbits[4] = { 0x08, 0x30, 0x20, 0x00 };
+	int flag = 0;
+
+	if ((R_LY < 0x91) && (R_LY == R_LYC))
+	{
+		R_STAT |= 0x04;
+		if (R_STAT & 0x40) flag = IF_STAT;
+	}
+	else R_STAT &= ~0x04;
+
+	if (R_STAT & condbits[R_STAT&3]) flag = IF_STAT;
+
+	if (!(R_LCDC & 0x80)) flag = 0;
+	
+	hw_interrupt(flag, IF_STAT);
+}
+
+void stat_write(byte b)
+{
+	R_STAT = (R_STAT & 0x07) | (b & 0x78);
+	if (!hw.cgb &&!(R_STAT & 2)) /* DMG STAT write bug => interrupt */
+		hw_interrupt(IF_STAT, IF_STAT);
+	stat_trigger();
+}
+
+
+/*
+ * stat_change is called when a transition results in a change to the
+ * LCD STAT condition (the low 2 bits of R_STAT).  It raises or lowers
+ * the VBLANK interrupt line appropriately and calls stat_trigger to
+ * update the STAT interrupt line.
+ */
+
+static void stat_change(int stat)
+{
+	stat &= 3;
+	R_STAT = (R_STAT & 0x7C) | stat;
+
+	if (stat != 1) hw_interrupt(0, IF_VBLANK);
+	/* hw_interrupt((stat == 1) ? IF_VBLANK : 0, IF_VBLANK); */
+	stat_trigger();
+}
+
+
+void lcdc_change(byte b)
+{
+	byte old = R_LCDC;
+	R_LCDC = b;
+	if ((R_LCDC ^ old) & 0x80) /* lcd on/off change */
+	{
+		R_LY = 0;
+		stat_change(2);
+		C = 40;
+		lcd_begin();
+	}
+}
+
+
+void lcdc_trans(void)
+{
+	if (!(R_LCDC & 0x80))
+	{
+		while (C <= 0)
+		{
+			switch ((byte)(R_STAT & 3))
+			{
+			case 0:
+			case 1:
+				stat_change(2);
+				C += 40;
+				break;
+			case 2:
+				stat_change(3);
+				C += 86;
+				break;
+			case 3:
+				stat_change(0);
+				if (hw.hdma & 0x80)
+					hw_hdma();
+				else
+					C += 102;
+				break;
+			}
+			return;
+		}
+	}
+	while (C <= 0)
+	{
+		switch ((byte)(R_STAT & 3))
+		{
+		case 1:
+			if (!(hw.ilines & IF_VBLANK))
+			{
+				C += 218;
+				hw_interrupt(IF_VBLANK, IF_VBLANK);
+				break;
+			}
+			if (R_LY == 0)
+			{
+				lcd_begin();
+				stat_change(2);
+				C += 40;
+				break;
+			}
+			else if (R_LY < 152)
+				C += 228;
+			else if (R_LY == 152)
+				C += 28;
+			else
+			{
+				R_LY = -1;
+				C += 200;
+			}
+			R_LY++;
+			stat_trigger();
+			break;
+		case 2:
+			lcd_refreshline();
+			stat_change(3);
+			C += 86;
+			break;
+		case 3:
+			stat_change(0);
+			if (hw.hdma & 0x80)
+				hw_hdma();
+			/* FIXME -- how much of the hblank does hdma use?? */
+			/* else */
+			C += 102;
+			break;
+		case 0:
+			if (++R_LY >= 144)
+			{
+				if (cpu.halt)
+				{
+					hw_interrupt(IF_VBLANK, IF_VBLANK);
+					C += 228;
+				}
+				else C += 10;
+				stat_change(1);
+				break;
+			}
+			stat_change(2);
+			C += 40;
+			break;
+		}
+	}
+}
+
+
+
+
+
+
+