mostly intact mbc1 impl

src/main.rs

@@ -1,4 +1,4 @@
-#![feature(exclusive_range_pattern)]
+#![feature(exclusive_range_pattern, let_chains)]
 
 mod processor;
 

src/processor/memory.rs

@@ -140,7 +140,7 @@ impl Memory {
             }
             0xA000..0xC000 => {
                 // cart ram
-                0xFF
+                self.rom.get_ram(address)
             }
             0xC000..0xE000 => {
                 return self.ram[(address - 0xC000) as usize];
@@ -178,7 +178,7 @@ impl Memory {
                 self.vram[(address - 0x8000) as usize] = data;
             }
             0xA000..0xC000 => {
-                // self.switchable_ram[(address - 0xA000) as usize] = data;
+                self.rom.set_ram(address, data);
             }
             0xC000..0xE000 => {
                 self.ram[(address - 0xC000) as usize] = data;

src/processor/memory/rom.rs

@@ -23,10 +23,15 @@ impl ROM {
         let _gbc_flag = data[0x143];
         let _sgb_flag = data[0x146];
         let rom_size = data[0x148];
-        let _ram_size = data[0x149];
+        let ram_size = data[0x149];
         let mbc: Box<dyn MBC> = match data[0x147] {
             0x00 => Box::new(NONE::init(data)),
-            0x01 => Box::new(MBC1::init(data, rom_size)),
+            0x01 => Box::new(MBC1::init(data, rom_size, 0, None)),
+            0x02 => Box::new(MBC1::init(data, rom_size, ram_size, None)),
+            0x03 => {
+                println!("MBC1 w/battery - battery not implemented!");
+                Box::new(MBC1::init(data, rom_size, ram_size, None))
+            }
             _ => panic!("unimplemented mbc: {:#X}", data[0x147]),
         };
         Self { title, mbc }
@@ -40,10 +45,18 @@ impl ROM {
         self.mbc.get(address)
     }
 
+    pub(super) fn get_ram(&self, address: Address) -> u8 {
+        self.mbc.get_ram(address)
+    }
+
     pub(super) fn set(&mut self, address: Address, data: u8) {
         self.mbc.set(address, data);
     }
 
+    pub(super) fn set_ram(&mut self, address: Address, data: u8) {
+        self.mbc.set_ram(address, data);
+    }
+
     pub fn mbc_type(&self) -> &str {
         self.mbc.mbc_type()
     }

src/processor/memory/rom/mbcs.rs

@@ -2,7 +2,9 @@ use crate::processor::memory::Address;
 
 pub(super) trait MBC {
     fn get(&self, address: Address) -> u8;
+    fn get_ram(&self, address: Address) -> u8;
     fn set(&mut self, address: Address, data: u8);
+    fn set_ram(&mut self, address: Address, data: u8);
     fn mbc_type(&self) -> &str;
 }
 
@@ -21,6 +23,12 @@ impl MBC for NONE {
         self.data[address as usize]
     }
 
+    fn get_ram(&self, _address: Address) -> u8 {
+        0xFF
+    }
+
+    fn set_ram(&mut self, _address: Address, _data: u8) {}
+
     fn set(&mut self, _address: Address, _data: u8) {
         return;
     }
@@ -32,21 +40,33 @@ impl MBC for NONE {
 
 #[derive(Clone, Copy)]
 enum BankingMode {
-    RomBanking,
-    RamBanking,
+    Simple,
+    Advanced,
 }
 
 pub(super) struct MBC1 {
     pub(super) data: Vec<u8>,
-    num_banks: usize,
-    bank_mode: BankingMode,
-    ram_enabled: bool,
+    rom_len: usize,
     rom_bank: u8,
+    ram_enabled: bool,
+    ram: Option<Vec<u8>>,
+    ram_bank: u8,
+    upper_banks: u8,
+    bank_mode: BankingMode,
 }
 
+const KB: usize = 1024;
+const ROM_BANK_SIZE: usize = 16 * KB;
+const RAM_BANK_SIZE: usize = 8 * KB;
+
 impl MBC1 {
-    pub(super) fn init(data: Vec<u8>, rom_size: u8) -> Self {
-        let num_banks = match rom_size {
+    pub(super) fn init(
+        data: Vec<u8>,
+        rom_size: u8,
+        ram_size: u8,
+        _save_file: Option<Vec<u8>>,
+    ) -> Self {
+        let rom_len = match rom_size {
             0x00 => 2,
             0x01 => 4,
             0x02 => 8,
@@ -60,23 +80,48 @@ impl MBC1 {
             0x53 => 80,
             0x54 => 96,
             _ => panic!("unacceptable rom size"),
+        } * ROM_BANK_SIZE;
+        // in kb
+        let ram = match ram_size {
+            0x00 => None,
+            0x01 => Some(vec![0; 2 * KB]),
+            0x02 => Some(vec![0; 8 * KB]),
+            0x03 => Some(vec![0; 32 * KB]),
+            0x04 => Some(vec![0; 128 * KB]),
+            0x05 => Some(vec![0; 64 * KB]),
+            _ => panic!("unacceptable ram size"),
         };
         Self {
             data,
-            num_banks,
-            bank_mode: BankingMode::RomBanking,
-            ram_enabled: false,
+            rom_len,
             rom_bank: 0x1,
+            ram_enabled: false,
+            ram,
+            ram_bank: 0,
+            upper_banks: 0,
+            bank_mode: BankingMode::Simple,
         }
     }
 }
 
 impl MBC for MBC1 {
     fn get(&self, address: Address) -> u8 {
-        match address {
-            0x0..0x4000 => self.data[address as usize],
-            0x4000..0x8000 => self.data[address as usize - (self.rom_bank as usize * 0x4000)],
-            _ => panic!("address too big for rom!"),
+        self.data[self.get_rom_addr(address)]
+    }
+
+    fn get_ram(&self, address: Address) -> u8 {
+        if self.ram_enabled && let Some(ram) = &self.ram {
+            let addr = self.get_ram_addr(address)%ram.len();
+            return ram[addr];
+        }
+        0xFF
+    }
+
+    fn set_ram(&mut self, address: Address, data: u8) {
+        let mut addr = self.get_ram_addr(address);
+        if self.ram_enabled && let Some(ram) = &mut self.ram {
+            addr = addr % ram.len();
+            ram[addr] = data;
         }
     }
 
@@ -92,25 +137,24 @@ impl MBC for MBC1 {
                 if set_data == 0 {
                     set_data = 1;
                 }
-                self.rom_bank = (self.rom_bank & 0b11100000) | set_data;
+                self.rom_bank = set_data;
             }
             0x4000..0x6000 => {
                 // ram bank OR upper bits 5 & 6 of rom bank
-                self.rom_bank = (self.rom_bank & 0b00011111) | ((data & 0b00000011) << 5);
+                self.upper_banks = data & 0b11;
             }
             0x6000..0x8000 => {
                 // mode select
                 self.bank_mode = if data == 0x1 {
-                    BankingMode::RamBanking
+                    BankingMode::Advanced
                 } else if data == 0x0 {
-                    BankingMode::RomBanking
+                    BankingMode::Simple
                 } else {
                     self.bank_mode
                 };
             }
             _ => {}
         }
-        self.rom_bank = (self.rom_bank as usize % self.num_banks) as u8;
         return;
     }
 
@@ -118,3 +162,41 @@ impl MBC for MBC1 {
         "MBC1"
     }
 }
+
+impl MBC1 {
+    fn get_rom_addr(&self, address: Address) -> usize {
+        (match address {
+            0x0..0x4000 => match self.bank_mode {
+                BankingMode::Simple => address as usize,
+                BankingMode::Advanced => {
+                    (address as usize) + (self.upper_banks as usize * 512 * KB)
+                }
+            },
+            0x4000..0x8000 => {
+                (address - 0x4000) as usize
+                    + (ROM_BANK_SIZE * self.rom_bank as usize)
+                    + (self.upper_banks as usize * 512 * KB)
+            }
+
+            0xA000..0xC000 => panic!("passed ram address to rom address function"),
+            _ => panic!("address {address} incompatible with MBC1"),
+        } % self.rom_len)
+    }
+
+    fn get_ram_addr(&self, address: Address) -> usize {
+        match address {
+            0x0..0x8000 => panic!("passed rom address to ram address function"),
+            0xA000..0xC000 => match self.bank_mode {
+                BankingMode::Simple => {
+                    (address - 0xA000) as usize + (RAM_BANK_SIZE * self.ram_bank as usize)
+                }
+                BankingMode::Advanced => {
+                    (address - 0xA000) as usize
+                        + (RAM_BANK_SIZE * self.ram_bank as usize)
+                        + (self.upper_banks as usize * 16 * KB)
+                }
+            },
+            _ => panic!("address {address} incompatible with MBC1"),
+        }
+    }
+}