Add mapper 468

src/boards/468_vrc3.h

@@ -0,0 +1,63 @@
+#define VRC3_prg   regByte[0]
+#define VRC3_latch regWord[0]
+#define VRC3_mode  regByte[1]
+#define VRC3_count regWord[1]
+
+static void VRC3_sync() {
+	int AND =prgAND >>1;
+	int OR  =prgOR >>1;
+	setprg16(0x8000, VRC3_prg &AND | OR &~AND);
+	setprg16(0xC000,           AND | OR &~AND);
+	setchr8(0);
+	setmirror(mapperFlags &4? MI_H: MI_V);
+}
+
+static DECLFW(VRC3_writeReg) {
+	int shift;
+	switch(A &0xF000) {
+	case 0x8000: case 0x9000: case 0xA000: case 0xB000:
+		V &=0xF;
+		shift =A >>10 &0xC;
+		VRC3_latch =VRC3_latch &~(0xF <<shift) | V <<shift;
+		break;
+	case 0xC000:
+		VRC3_mode =V;
+		if (VRC3_mode &0x02) VRC3_count =VRC3_latch;
+		X6502_IRQEnd(FCEU_IQEXT);
+		break;
+	case 0xD000:
+		VRC3_mode =VRC3_mode &~0x02 | VRC3_mode <<1 &0x02;
+		X6502_IRQEnd(FCEU_IQEXT);
+		break;
+	case 0xF000:
+		VRC3_prg =V;
+		sync();
+		break;
+	}
+}
+
+static void FP_FASTAPASS(1) VRC3_cpuCycle(int a) {
+	while (a--) {
+		int mask =VRC3_mode &0x04? 0xFF: 0xFFFF;
+		if (VRC3_mode &0x02) {
+			if ((VRC3_count &mask) ==mask) {
+				VRC3_count =VRC3_latch;
+				X6502_IRQBegin(FCEU_IQEXT);
+			} else
+				++VRC3_count;
+		}
+	}
+}
+
+void VRC3_reset(uint8 clearRegs) {
+	sync =VRC3_sync;
+	prgAND =0x0F;
+	MapIRQHook =VRC3_cpuCycle;
+	SetWriteHandler(0x8000, 0xFFFF, VRC3_writeReg);
+	sync();
+}
+
+#undef VRC3_prg
+#undef VRC3_latch
+#undef VRC3_mode
+#undef VRC3_count