From eb62d598178fdcb3d354418e5260304d247f6015 Mon Sep 17 00:00:00 2001
From: Kevin Hamacher <kevin.hamacher@ruhr-uni-bochum.de>
Date: Fri, 14 Feb 2020 13:15:52 +0100
Subject: [PATCH] Add support for MBC5

---
 src/cartridge.rs |   5 ++-
 src/mbc/mbc5.rs  | 112 +++++++++++++++++++++++++++++++++++++++++++++++
 src/mbc/mod.rs   |   1 +
 3 files changed, 117 insertions(+), 1 deletion(-)
 create mode 100644 src/mbc/mbc5.rs

diff --git a/src/cartridge.rs b/src/cartridge.rs
index c666490..c694d8b 100644
--- a/src/cartridge.rs
+++ b/src/cartridge.rs
@@ -1,4 +1,4 @@
-use crate::mbc::{mbc, mbc1, mbc2, mbc3};
+use crate::mbc::{mbc, mbc1, mbc2, mbc3, mbc5};
 
 #[derive(Debug, PartialEq)]
 enum MemoryBankControllerType {
@@ -6,6 +6,7 @@ enum MemoryBankControllerType {
     MBC1,
     MBC2,
     MBC3,
+    MBC5,
     //HuC1,
 }
 
@@ -29,6 +30,7 @@ impl Cartridge {
             0x01..=0x03 => MemoryBankControllerType::MBC1,
             0x05..=0x06 => MemoryBankControllerType::MBC2,
             0x0F..=0x13 => MemoryBankControllerType::MBC3,
+            0x19..=0x1E => MemoryBankControllerType::MBC5,
             // 0xFF => MemoryBankControllerType::HuC1,
             _ => panic!("Unsupported MBC type: {:02X}", rom[0x0147]),
         };
@@ -62,6 +64,7 @@ impl Cartridge {
             MemoryBankControllerType::MBC1 => Box::new(mbc1::MBC1::new(rom, ram)),
             MemoryBankControllerType::MBC2 => Box::new(mbc2::MBC2::new(rom, ram)),
             MemoryBankControllerType::MBC3 => Box::new(mbc3::MBC3::new(rom, ram)),
+            MemoryBankControllerType::MBC5 => Box::new(mbc5::MBC5::new(rom, ram)),
         };
 
         Cartridge {
diff --git a/src/mbc/mbc5.rs b/src/mbc/mbc5.rs
new file mode 100644
index 0000000..7cf4d23
--- /dev/null
+++ b/src/mbc/mbc5.rs
@@ -0,0 +1,112 @@
+use super::mbc::MBC;
+
+pub struct MBC5 {
+    rom: Box<[u8]>,
+    ram: Box<[u8]>,
+    rom_bank_no: u16,
+    ram_bank_no: u8,
+    ram_rtc_enabled: bool,
+}
+
+impl MBC5 {
+    pub fn new(rom: Box<[u8]>, ram: Box<[u8]>) -> Self {
+        MBC5 {
+            rom: rom,
+            ram: ram,
+            rom_bank_no: 1,
+            ram_bank_no: 0,
+            ram_rtc_enabled: false,
+        }
+    }
+    fn active_rom_bank(&self) -> u16 {
+        self.rom_bank_no
+    }
+
+    fn active_ram_bank(&self) -> u8 {
+        self.ram_bank_no
+    }
+}
+
+impl MBC for MBC5 {
+    fn dump_ram(&self, file: &String) {
+        use crate::write_file;
+        write_file(&file, &self.ram).expect("Saving failed");
+    }
+
+    fn read_byte(&self, addr: u16) -> u8 {
+        match addr {
+            0x0000..=0x3FFF => self.rom[addr as usize],
+            0x4000..=0x7FFF => {
+                let addr = addr - 0x4000;
+                let abs_addr: usize = addr as usize + self.active_rom_bank() as usize * 0x4000;
+                let val: u8 = self.rom[abs_addr];
+                val
+            }
+            0xA000..=0xBFFF => {
+                let addr = addr - 0xA000;
+                match self.active_ram_bank() {
+                    0x00..=0x03 => {
+                        self.ram[self.active_ram_bank() as usize * 0x2000 + addr as usize]
+                    }
+                    0x08..=0x0C => {
+                        // TODO
+                        println!("MBC5: Ignoring RTC read");
+                        0
+                    }
+                    _ => panic!(
+                        "MBC5: Accessing unknown RAM bank {:02X}",
+                        self.active_ram_bank()
+                    ),
+                }
+            }
+            _ => {
+                panic!("MBC5: Unable to read from {:04X}", addr);
+            }
+        }
+    }
+
+    fn write_byte(&mut self, addr: u16, val: u8) {
+        match addr {
+            0x0000..=0x1FFF => match val {
+                0x0A => self.ram_rtc_enabled = true,
+                0x00 => self.ram_rtc_enabled = false,
+                _ => println!("MBC5: Unknown MBC value {:02X} for {:04X}", val, addr),
+            },
+            // Lower part rom bank select
+            0x2000..=0x2FFF => self.rom_bank_no = (self.rom_bank_no & (!0xFF)) | u16::from(val),
+            0x3000..=0x3FFF => {
+                self.rom_bank_no = (self.rom_bank_no & (0xFF)) | ((u16::from(val) & 1) << 8)
+            }
+            0x4000..=0x5FFF => {
+                // RAM bank select
+                self.ram_bank_no = val & 0x0F;
+            }
+            0x6000..=0x7FFF => {
+                // Latch clock data
+                match val {
+                    0x00 => println!("latch = 0"),
+                    0x01 => println!("latch = 1"), // TODO: This should copy the current clock to the register
+                    _ => panic!("MBC5: Unknown latch value {:02X}", val),
+                }
+            }
+            0xA000..=0xBFFF => {
+                let addr = addr - 0xA000;
+                match self.active_ram_bank() {
+                    0x00..=0x03 => {
+                        let active_bank = self.active_ram_bank() as usize;
+                        self.ram[active_bank * 0x2000 + addr as usize] = val;
+                    }
+                    0x08..=0x0C => {
+                        // TODO
+                        println!("MBC5: Ignoring RTC write ({:02X})", val);
+                    }
+                    _ => panic!(
+                        "MBC5: Writing unknown RAM bank {:02X}",
+                        self.active_ram_bank()
+                    ),
+                }
+            }
+            _ => panic!("MBC5: Writing {:02X} to {:04X} not supported", val, addr),
+        }
+    }
+}
diff --git a/src/mbc/mod.rs b/src/mbc/mod.rs
index fdcb7ca..889428c 100644
--- a/src/mbc/mod.rs
+++ b/src/mbc/mod.rs
@@ -2,3 +2,4 @@ pub mod mbc;
 pub mod mbc1;
 pub mod mbc2;
 pub mod mbc3;
+pub mod mbc5;