chore: stub vram, start work on ppu, fix set_register bug

src/bus.rs

@@ -2,8 +2,9 @@ use super::cartridge::Cartridge;
 
 #[derive(Debug, Clone)]
 pub struct Bus {
-    boot: Option<[u8; 256]>,
+    boot: Option<[u8; 256]>, // Boot ROM is 256b long
     cartridge: Option<Cartridge>,
+    vram: [u8; 8192], // 8KB of VRAM
 }
 
 impl Default for Bus {
@@ -11,6 +12,7 @@ impl Default for Bus {
         Self {
             boot: Some(include_bytes!("../bin/DMG_ROM.bin").to_owned()),
             cartridge: None,
+            vram: [0; 8192],
         }
     }
 }
@@ -23,7 +25,7 @@ impl Bus {
     pub fn without_boot() -> Self {
         Self {
             boot: None,
-            cartridge: None,
+            ..Default::default()
         }
     }
 
@@ -54,7 +56,7 @@ impl Bus {
             },
             0x8000..=0x9FFF => {
                 // 8KB Video RAM
-                unimplemented!("Unable to read {:#06X} in Video RAM", addr);
+                self.vram[(addr - 0x8000) as usize]
             }
             0xA000..=0xBFFF => {
                 // 8KB External RAM
@@ -87,13 +89,62 @@ impl Bus {
             }
             0xFFFF => {
                 // Interupts Enable Register
-                unimplemented!("Unable to read Interrupt Enable Register {:#06X} ", addr);
+                unimplemented!("Unable to read IE Register {:#06X} ", addr);
             }
         }
     }
 
     pub fn write_byte(&mut self, addr: u16, byte: u8) {
-        unimplemented!("Can't write {:#04x} to {:#06X}", byte, addr)
+        match addr {
+            0x0000..=0x3FFF => {
+                // 16KB ROM bank 00
+                panic!("Tried to write to {:#06X} in ROM Bank 00", addr);
+            }
+            0x4000..=0x7FFF => {
+                // 16KB ROM Bank 01 -> NN (switchable via MB)
+                panic!("Tried to write to {:#06X} in ROM Bank 01 -> NN", addr);
+            }
+            0x8000..=0x9FFF => {
+                // 8KB Video RAM
+                self.vram[(addr - 0x8000) as usize] = byte;
+            }
+            0xA000..=0xBFFF => {
+                // 8KB External RAM
+                unimplemented!("Unable to write to {:#06X} in Extermal RAM", addr);
+            }
+            0xC000..=0xCFFF => {
+                // 4KB Work RAM Bank 0
+                unimplemented!("Unable to write to {:#06X} in Work RAM Bank 0", addr);
+            }
+            0xD000..=0xDFFF => {
+                // 4KB Work RAM Bank 1 -> N
+                unimplemented!("Unable to write to {:#06X} in Work RAM Bank N", addr);
+            }
+            0xE000..=0xFDFF => {
+                // Mirror of 0xC000 to 0xDDFF
+                unimplemented!("Unable to write to {:#06X} in Restricted Mirror", addr);
+            }
+            0xFE00..=0xFE9F => {
+                // Sprite Attrbute Table
+                unimplemented!(
+                    "Unable to write to {:#06X} in the Sprite Attribute Table",
+                    addr
+                );
+            }
+            0xFEA0..=0xFEFF => unimplemented!("{:#06X} is not allowed to be used", addr),
+            0xFF00..=0xFF7F => {
+                // IO Registers
+                unimplemented!("Unable to write to {:#06X} in I/O Registers", addr);
+            }
+            0xFF80..=0xFFFE => {
+                // High RAM
+                unimplemented!("Unable to write to {:#06X} in High RAM", addr);
+            }
+            0xFFFF => {
+                // Interupts Enable Register
+                unimplemented!("Unable to write to IE Register {:#06X} ", addr);
+            }
+        }
     }
 
     pub fn read_word(&self, addr: u16) -> u16 {
@@ -117,7 +168,8 @@ impl Bus {
             },
             0x8000..=0x9FFF => {
                 // 8KB Video RAM
-                unimplemented!("Unable to read {:#06X} in Video RAM", addr);
+                (self.vram[((addr + 1) - 0x8000) as usize] as u16) << 8
+                    | self.vram[(addr - 0x8000) as usize] as u16
             }
             0xA000..=0xBFFF => {
                 // 8KB External RAM
@@ -150,7 +202,7 @@ impl Bus {
             }
             0xFFFF => {
                 // Interupts Enable Register
-                unimplemented!("Unable to read Interrupt Enable Register {:#06X} ", addr);
+                unimplemented!("Unable to read IE Register {:#06X} ", addr);
             }
         }
     }