From ddc63f98b2d2b293c1b50332af24835f97fba575 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Tue, 28 Jun 2022 23:02:53 +0100
Subject: [PATCH] feat: better memory mapping
---
src/cpu.rs | 79 ++++++++++++++++++++++++++++++++++++++++++++-----
src/gb.rs | 3 +-
src/mmu.rs | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++---
3 files changed, 155 insertions(+), 14 deletions(-)
diff --git a/src/cpu.rs b/src/cpu.rs
index d663cdf8..a28049fd 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -28,7 +28,7 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
(nop, 4, "NOP"),
(nop, 4, "NOP"),
(nop, 4, "NOP"),
- (nop, 4, "NOP"),
+ (rla, 4, "RLA"),
(nop, 4, "NOP"),
(nop, 4, "NOP"),
(ld_a_mde, 8, "LD A, [DE]"),
@@ -208,8 +208,8 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
(nop, 4, "NOP"),
(nop, 4, "NOP"),
// 0xc opcodes
- (nop, 4, "NOP"),
- (nop, 4, "NOP"),
+ (ret_nz, 8, "RET NZ"),
+ (pop_bc, 12, "POP BC"),
(nop, 4, "NOP"),
(nop, 4, "NOP"),
(nop, 4, "NOP"),
@@ -297,7 +297,7 @@ pub const BITWISE: [(fn(&mut Cpu), u8, &'static str); 176] = [
(nop, 4, "NOP"),
// 0x1 opcodes
(nop, 4, "NOP"),
- (nop, 4, "NOP"),
+ (rl_c, 8, "RL C"),
(nop, 4, "NOP"),
(nop, 4, "NOP"),
(nop, 4, "NOP"),
@@ -514,9 +514,10 @@ impl Cpu {
let mut opcode = self.mmu.read(self.pc);
self.pc = self.pc.wrapping_add(1);
+ let is_prefix = opcode == PREFIX;
let instruction: &(fn(&mut Cpu), u8, &str);
- if opcode == PREFIX {
+ if is_prefix {
opcode = self.mmu.read(self.pc);
self.pc = self.pc.wrapping_add(1);
instruction = &BITWISE[opcode as usize];
@@ -526,7 +527,10 @@ impl Cpu {
let (instruction_fn, instruction_size, instruction_str) = instruction;
- println!("{}\t(0x{:02x})\t${:04x}", instruction_str, opcode, pc);
+ println!(
+ "{}\t(0x{:02x})\t${:04x} {}",
+ instruction_str, opcode, pc, is_prefix
+ );
instruction_fn(self);
self.ticks = self.ticks.wrapping_add(*instruction_size as u32);
@@ -614,7 +618,7 @@ impl Cpu {
}
#[inline(always)]
- fn push_byte(&mut self, byte: u8){
+ fn push_byte(&mut self, byte: u8) {
self.sp -= 1;
self.mmu.write(self.sp, byte);
}
@@ -625,6 +629,19 @@ impl Cpu {
self.push_byte(word as u8);
}
+ #[inline(always)]
+ fn pop_byte(&mut self) -> u8 {
+ let byte = self.mmu.read(self.sp);
+ self.sp += 1;
+ byte
+ }
+
+ #[inline(always)]
+ fn pop_word(&mut self) -> u16 {
+ let word = self.pop_byte() as u16 | ((self.pop_byte() as u16) << 8);
+ word
+ }
+
#[inline(always)]
fn get_zero(&self) -> bool {
self.zero
@@ -748,6 +765,18 @@ fn ld_de_u16(cpu: &mut Cpu) {
cpu.set_de(word);
}
+fn rla(cpu: &mut Cpu) {
+ let carry = cpu.get_carry();
+
+ cpu.set_carry(cpu.a & 0x80 == 0x80);
+
+ cpu.a = cpu.a << 1 | carry as u8;
+
+ cpu.set_sub(false);
+ cpu.set_zero(false);
+ cpu.set_half_carry(false);
+}
+
fn ld_a_mde(cpu: &mut Cpu) {
let byte = cpu.mmu.read(cpu.de());
cpu.a = byte;
@@ -796,6 +825,20 @@ fn xor_a_a(cpu: &mut Cpu) {
cpu.set_carry(false);
}
+fn ret_nz(cpu: &mut Cpu) {
+ if cpu.get_zero() {
+ return;
+ }
+
+ cpu.pc = cpu.pop_word();
+ cpu.ticks = cpu.ticks.wrapping_add(12);
+}
+
+fn pop_bc(cpu: &mut Cpu) {
+ let word = cpu.pop_word();
+ cpu.set_bc(word);
+}
+
fn push_bc(cpu: &mut Cpu) {
cpu.push_word(cpu.bc());
}
@@ -815,10 +858,31 @@ fn ld_mff00c_a(cpu: &mut Cpu) {
cpu.mmu.write(0xff0c + cpu.c as u16, cpu.a);
}
+fn rl_c(cpu: &mut Cpu) {
+ cpu.c = rl(cpu, cpu.c);
+}
+
fn bit_7_h(cpu: &mut Cpu) {
bit_h(cpu, 7);
}
+/// Helper function that rotates (shifts) the given
+/// byte (probably from a register) and updates the
+/// proper flag registers.
+fn rl(cpu: &mut Cpu, byte: u8) -> u8 {
+ let carry = cpu.get_carry();
+
+ cpu.set_carry(byte & 0x80 == 0x80);
+
+ let result = (byte << 1) | carry as u8;
+
+ cpu.set_sub(false);
+ cpu.set_zero(result == 0);
+ cpu.set_half_carry(false);
+
+ result
+}
+
/// Helper function to test one bit in a u8.
/// Returns true if bit is 0.
fn bit_zero(val: u8, bit: u8) -> bool {
@@ -826,7 +890,6 @@ fn bit_zero(val: u8, bit: u8) -> bool {
}
fn bit_h(cpu: &mut Cpu, bit: u8) {
- println!("{}", cpu.h);
cpu.set_sub(false);
cpu.set_zero(bit_zero(cpu.h, bit));
cpu.set_half_carry(true);
diff --git a/src/gb.rs b/src/gb.rs
index 8b2a4a9b..0d1da401 100644
--- a/src/gb.rs
+++ b/src/gb.rs
@@ -26,8 +26,7 @@ impl GameBoy {
pub fn load_boot(&mut self, path: &str) {
let data = read_file(path);
- self.cpu.mmu().write_buffer(0x0000, &data);
- println!("LOADED BOOT")
+ self.cpu.mmu().write_boot(0x0000, &data);
}
pub fn load_boot_default(&mut self) {
diff --git a/src/mmu.rs b/src/mmu.rs
index d2adbdd7..3cd912f1 100644
--- a/src/mmu.rs
+++ b/src/mmu.rs
@@ -1,29 +1,103 @@
use crate::ppu::Ppu;
+pub const BIOS_SIZE: usize = 256;
+pub const ROM_SIZE: usize = 32768;
pub const RAM_SIZE: usize = 8192;
+pub const ERAM_SIZE: usize = 8192;
+pub const HRAM_SIZE: usize = 128;
pub struct Mmu {
ppu: Ppu,
+ boot_active: bool,
+ boot: [u8; BIOS_SIZE],
+ rom: [u8; ROM_SIZE],
ram: [u8; RAM_SIZE],
+ eram: [u8; RAM_SIZE],
+ hram: [u8; HRAM_SIZE],
}
impl Mmu {
pub fn new(ppu: Ppu) -> Mmu {
Mmu {
ppu: ppu,
+ boot_active: true,
+ boot: [0u8; BIOS_SIZE],
+ rom: [0u8; ROM_SIZE],
ram: [0u8; RAM_SIZE],
+ eram: [0u8; ERAM_SIZE],
+ hram: [0u8; HRAM_SIZE],
}
}
pub fn read(&self, addr: u16) -> u8 {
- self.ram[addr as usize]
+ match addr & 0xf000 {
+ // BIOS
+ 0x0000 => {
+ //@todo we still need to control if we're reading from boot
+ // if(MMU._inboot)
+ // {
+ // if(addr < 0x0100)
+ // return MMU._boot[addr];
+ // else if(Z80._r.pc == 0x0100)
+ // MMU._inboot = 0;
+ //}
+ //return MMU._rom[addr];
+ if self.boot_active {
+ if addr < 0x0100 {
+ return self.boot[addr as usize];
+ }
+ //else if self @todo implementar isto
+ }
+ self.rom[addr as usize]
+ }
+ // ROM0
+ 0x1000 | 0x2000 | 0x3000 => self.rom[addr as usize],
+ // ROM1 (unbanked) (16k)
+ 0x4000 | 0x5000 | 0x6000 | 0x7000 => self.rom[addr as usize],
+ // Graphics: VRAM (8k)
+ 0x8000 | 0x9000 => {
+ println!("READING FROM VRAM");
+ self.ppu.vram[(addr & 0x1fff) as usize]
+ }
+ // External RAM (8k)
+ 0xa000 | 0xb000 => {
+ println!("READING FROM ERAM");
+ self.eram[(addr & 0x1fff) as usize]
+ }
+ // Working RAM (8k)
+ 0xc000 | 0xd000 => self.ram[(addr & 0x1fff) as usize],
+ // Working RAM shadow
+ 0xe000 => {
+ println!("READING FROM RAM Shadow");
+ self.ram[(addr & 0x1fff) as usize]
+ }
+ // Working RAM shadow, I/O, Zero-page RAM
+ 0xf000 => match addr & 0x0f00 {
+ 0x000 | 0x100 | 0x200 | 0x300 | 0x400 | 0x500 | 0x600 | 0x700 | 0x800 | 0x900
+ | 0xa00 | 0xb00 | 0xc00 | 0xd00 => self.ram[(addr & 0x1fff) as usize],
+ 0xe00 => {
+ println!("READING FROM GPU OAM - NOT IMPLEMENTED");
+ 0x00
+ }
+ 0xf00 => {
+ if addr >= 0xff80 {
+ self.ram[(addr & 0x7f) as usize]
+ } else {
+ println!("WRITING TO IO control");
+ 0x00
+ }
+ }
+ addr => panic!("Reading from unknown location 0x{:04x}", addr),
+ },
+ addr => panic!("Reading from unknown location 0x{:04x}", addr),
+ }
}
pub fn write(&mut self, addr: u16, value: u8) {
match addr & 0xf000 {
- // BIOS
+ // BOOT
0x0000 => {
- println!("WRITING to BIOS")
+ println!("WRITING to BOOT")
}
// ROM0
0x1000 | 0x2000 | 0x3000 => {
@@ -64,6 +138,7 @@ impl Mmu {
0xf00 => {
if addr >= 0xff80 {
println!("WRITING TO Zero page");
+ self.hram[(addr & 0x7f) as usize] = value;
} else {
println!("WRITING TO IO control");
}
@@ -74,7 +149,11 @@ impl Mmu {
}
}
- pub fn write_buffer(&mut self, addr: u16, buffer: &[u8]) {
+ pub fn write_boot(&mut self, addr: u16, buffer: &[u8]) {
+ self.boot[addr as usize..addr as usize + buffer.len()].clone_from_slice(buffer);
+ }
+
+ pub fn write_ram(&mut self, addr: u16, buffer: &[u8]) {
self.ram[addr as usize..addr as usize + buffer.len()].clone_from_slice(buffer);
}
}
--
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