more mbc work

src/mbc.cpp

@@ -1 +1,44 @@
+#include "addressSpace.hpp"
 #include "gameboy.hpp"
+
+void AddressSpace::determineMBCInfo() {
+	MBC = static_cast<MBCType>(memoryLayout.romBank0[0x147]);
+	romSize = 32768 * (1 << memoryLayout.romBank0[0x147]);
+	romBanks = (1 << (memoryLayout.romBank0[0x147] + 1));
+
+	switch (memoryLayout.romBank0[0x0149]) {
+	case 0x02:
+		externalRamSize = 8196;
+		externalRamBanks = 1;
+		break;
+	case 0x03:
+		externalRamSize = 32768;
+		externalRamBanks = 4;
+		break;
+	case 0x04:
+		externalRamSize = 131072;
+		externalRamBanks = 16;
+		break;
+	case 0x05:
+		externalRamSize = 65536;
+		externalRamBanks = 8;
+		break;
+	default:
+		externalRamSize = 0;
+		externalRamBanks = 0;
+		break;
+	}
+
+	if (MBC == MBC2 || MBC2Battery) {
+		//only the lower 4 bits are usable
+		externalRamSize = 512;
+	}
+}
+
+bool GameBoy::testMBCWrite(const Byte& address) {
+	const Byte* ptr = &address;
+	if (ptr >= &addressSpace[0x0] && ptr <= &addressSpace[0x7FFF])
+		return true;
+	return false;
+}
+