Compute 2bpp background framebuffer (#4)

snes-core/src/cpu/instructions/brl.rs

@@ -24,7 +24,7 @@ impl CPUInstruction for BRL {
     }
 
     fn mnemonic(&self, registers: &Registers, bus: &Bus, opcode: u8) -> String {
-        decoder_common::mnemonic_absolute(opcode, INSTR_NAME, registers, bus)
+        decoder_common::mnemonic_absolute_16bit(opcode, INSTR_NAME, registers, bus)
     }
 }
 

snes-core/src/cpu/instructions/decoder_common.rs

@@ -10,7 +10,10 @@ pub fn mnemonic_arithmetic(is_16bit: bool, opcode: u8, instr_name: &str, address
             true =>  mnemonic_16bit_immediate(opcode, instr_name, registers, bus),
             false => mnemonic_8bit_immediate(opcode, instr_name, registers, bus),
         },
-        A::Absolute => mnemonic_absolute(opcode, instr_name, registers, bus),
+        A::Absolute => match is_16bit {
+            true => mnemonic_absolute_16bit(opcode, instr_name, registers, bus),
+            false => mnemonic_absolute_8bit(opcode, instr_name, registers, bus),
+        },
         A::AbsoluteLong => mnemonic_absolute_long(opcode, instr_name, registers, bus),
         A::DirectPage => mnemonic_direct_page(opcode, instr_name, registers, bus),
         A::DirectPageIndirect => mnemonic_direct_page_indirect(opcode, instr_name, registers, bus),
@@ -38,14 +41,21 @@ pub fn mnemonic_8bit_immediate(opcode: u8, instr_name: &str, registers: &Registe
 pub fn mnemonic_16bit_immediate(opcode: u8, instr_name: &str, registers: &Registers, bus: &Bus) -> String {
     let next_byte = bus.read_external(registers.get_pc_address() + 1);
     let next_second_byte = bus.read_external(registers.get_pc_address() + 2);
-    let word = (next_byte as u16) | ((next_byte as u16) << 8);
+    let word = (next_byte as u16) | ((next_second_byte as u16) << 8);
     format!("{:02X} {:02X} {:02X} __ | {} #${:04X}", opcode, next_byte, next_second_byte, instr_name, word)
 }
 
-pub fn mnemonic_absolute(opcode: u8, instr_name: &str, registers: &Registers, bus: &Bus) -> String {
+pub fn mnemonic_absolute_8bit(opcode: u8, instr_name: &str, registers: &Registers, bus: &Bus) -> String {
     let next_byte = bus.read_external(registers.get_pc_address() + 1);
     let next_second_byte = bus.read_external(registers.get_pc_address() + 2);
-    let word = (next_byte as u16) | ((next_byte as u16) << 8);
+    let word = (next_byte as u16) | ((next_second_byte as u16) << 8);
+    format!("{:02X} {:02X} {:02X} __ | {} ${:04X}", opcode, next_byte, next_second_byte, instr_name, word)
+}
+
+pub fn mnemonic_absolute_16bit(opcode: u8, instr_name: &str, registers: &Registers, bus: &Bus) -> String {
+    let next_byte = bus.read_external(registers.get_pc_address() + 1);
+    let next_second_byte = bus.read_external(registers.get_pc_address() + 2);
+    let word = (next_byte as u16) | ((next_second_byte as u16) << 8);
     format!("{:02X} {:02X} {:02X} __ | {} ${:04X}", opcode, next_byte, next_second_byte, instr_name, word)
 }
 

snes-core/src/cpu/instructions/pea.rs

@@ -19,7 +19,7 @@ impl CPUInstruction for PEA {
     }
 
     fn mnemonic(&self, registers: &Registers, bus: &Bus, opcode: u8) -> String {
-        decoder_common::mnemonic_absolute(opcode, INSTR_NAME, registers, bus)
+        decoder_common::mnemonic_absolute_16bit(opcode, INSTR_NAME, registers, bus)
     }
 }
 

snes-core/src/cpu/instructions/per.rs

@@ -24,7 +24,7 @@ impl CPUInstruction for PER {
     }
 
     fn mnemonic(&self, registers: &Registers, bus: &Bus, opcode: u8) -> String {
-        decoder_common::mnemonic_absolute(opcode, INSTR_NAME, registers, bus)
+        decoder_common::mnemonic_absolute_16bit(opcode, INSTR_NAME, registers, bus)
     }
 }
 

snes-core/src/cpu/internal_registers.rs

@@ -57,9 +57,11 @@ impl InternalRegisters {
     }
 
     fn read_vblank_nmi_mut(&self, ppu_registers: &mut PPURegisters) -> u8 {
-        let byte = self._read(RDNMI);
+        let result = self.read_vblank_nmi(ppu_registers);
+        if result == 0x80 {
+            println!("nmi set");
+        }
         // When register is read, bit 7 is cleared
-        let result = (byte & 0x7F) | ((ppu_registers.vblank_nmi as u8) << 7);
         ppu_registers.vblank_nmi = false;
         result
     }

snes-core/src/ppu/registers.rs

@@ -111,7 +111,7 @@ pub enum BgSize {
     T32x32,
     T64x32, // V Mirror
     T32x64, // H Mirror
-    T64x64, // H Mirror
+    T64x64, // H/V Mirror
 }
 
 impl BgSize {
@@ -266,10 +266,10 @@ impl PPURegisters {
     pub fn get_bg_tile_size(&self, background: Background) -> TileSize {
         let byte = self._read(BGMODE);
         let bit = match background {
-            Background::Bg1 => byte >> 3 & 0b1 == 1, // Bit 4
-            Background::Bg2 => byte >> 4 & 0b1 == 1, // Bit 5
-            Background::Bg3 => byte >> 5 & 0b1 == 1, // Bit 6
-            Background::Bg4 => byte >> 6 & 0b1 == 1, // Bit 7
+            Background::Bg1 => byte >> 4 & 0b1 == 1, // Bit 4
+            Background::Bg2 => byte >> 5 & 0b1 == 1, // Bit 5
+            Background::Bg3 => byte >> 6 & 0b1 == 1, // Bit 6
+            Background::Bg4 => byte >> 7 & 0b1 == 1, // Bit 7
         };
         match bit {
             true => TileSize::P16x16,
@@ -393,9 +393,9 @@ mod ppu_registers_test {
     #[test]
     fn test_get_bg_tile_size() {
         let mut registers = PPURegisters::new();
-        registers.write(BGMODE, 0b00000100);
+        registers.write(BGMODE, 0b00000000);
         assert_eq!(registers.get_bg_tile_size(Background::Bg1), TileSize::P8x8);
-        registers.write(BGMODE, 0b00001100);
+        registers.write(BGMODE, 0b00010000);
         assert_eq!(registers.get_bg_tile_size(Background::Bg1), TileSize::P16x16);
     }
 

snes-core/src/rom/lo_rom.rs

@@ -27,7 +27,7 @@ impl ROM for LoROM {
         let address = LoROM::adjust_address(address);
         match self.data.get(address as usize) {
             Some(byte) => *byte,
-            None => 0xFF,
+            None => 0x00,
         }
     }