add mapper #66 (GXROM)

1 files changed, 27 insertions, 0 deletions

diff --git a/mapper_gxrom.c b/mapper_gxrom.c
new file mode 100644
index 0000000..e03f9d2
--- /dev/null
+++ b/mapper_gxrom.c
@@ -0,0 +1,27 @@
+
+static void mapper_66_init(struct nes_state *state) {
+	state->map.gxrom.prg_offset = 0;
+	state->map.gxrom.chr_offset = 0;
+}
+
+static uint8_t mapper_66_read(struct nes_state *state, uint32_t addr) {
+	if(addr >= 0x8000) {
+		uint32_t base = state->map.gxrom.prg_offset;
+		return state->rom[base + (addr - 0x8000)];
+	}
+	return 0;
+}
+
+static void mapper_66_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.gxrom.prg_offset = prg_bank * 0x8000;
+		state->map.gxrom.chr_offset = chr_bank * 0x2000;
+	}
+}
+
+static void mapper_66_tick(struct nes_state *state) {
+	// No IRQ or timing logic needed
+}