cleanup and rewrite of memory_read()

1 files changed, 21 insertions, 3 deletions

diff --git a/memory.c b/memory.c
index 74b0a0f..6e0c6df 100644
--- a/memory.c
+++ b/memory.c
@@ -7,10 +7,27 @@ static uint8_t memory_read(struct nes_state *restrict state, uint32_t offset) {
 	ppu_tick(state);
 	// apu_tick(state);
 
-	if(LIKELY(offset < 0x2000)) {
+	if(LIKELY(offset >= 0x6000)) {	// MOST
+		return state->mapper.prg_read(state, offset);
+
+	} else if(LIKELY(offset < 0x2000)) {	// SECOND
 		return state->ram[offset & 0x07ff];
 
-	} else if(offset < 0x4000) {
+	} else if(offset < 0x4000) {	// THIRD
+		return ppu_read(state, offset);
+
+	} else if(offset == 0x4016 || offset == 0x4017) {
+		uint32_t index = offset & 1;
+		uint8_t value = (state->ppu.input_latch[index] >> state->ppu.input_bit[index]) & 1;
+		state->ppu.input_bit[index]++;
+		return value | 0x40;	// Bit 6 open bus high, bit 7 low
+	}
+
+#if 0
+	if(LIKELY(offset < 0x2000)) {	// SECOND
+		return state->ram[offset & 0x07ff];
+
+	} else if(offset < 0x4000) {	// THIRD
 		return ppu_read(state, offset);
 
 	} else if(offset == 0x4016 || offset == 0x4017) {
@@ -23,10 +40,11 @@ static uint8_t memory_read(struct nes_state *restrict state, uint32_t offset) {
 	// 	static uint32_t apuread = 0;
 	// 	// printf("%.5d apu\n", apuread++);
 
-	} else if(LIKELY(offset >= 0x6000)) {
+	} else if(LIKELY(offset >= 0x6000)) {	// MOST
 		return state->mapper.prg_read(state, offset);
 
 	}
+#endif
 	return 0;
 }