1 files changed, 30 insertions, 0 deletions
diff --git a/mapper_0042.c b/mapper_0042.c
new file mode 100644
index 0000000..4cf4c86
--- /dev/null
+++ b/mapper_0042.c
@@ -0,0 +1,30 @@
+
+static void mapper_0042_init(struct nes_state *state) {
+	state->map.m0042.prg_offset = 0;
+	state->map.m0042.chr_offset = 0;
+}
+
+static uint8_t mapper_0042_prg_read(struct nes_state *state, uint32_t addr) {
+	if(addr >= 0x8000) {
+		uint32_t base = state->map.m0042.prg_offset;
+		return state->prg_rom[base + (addr - 0x8000)];
+	}
+	return 0;
+}
+
+static void mapper_0042_prg_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	if(addr >= 0x8000) {
+		uint32_t prg_bank = (value >> 4) & 3;
+		uint32_t chr_bank = (value >> 0) & 3;
+
+		state->map.m0042.prg_offset = prg_bank * 0x8000;
+		state->map.m0042.chr_offset = chr_bank * 0x2000;
+	}
+}
+
+static uint8_t mapper_0042_chr_read(struct nes_state *state, uint32_t addr) {
+	return state->chr_rom[state->map.m0042.chr_offset + addr];
+}
+
+static void mapper_0042_chr_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+}