use crate::cartridge::base_mapper::BaseMapper;
use crate::cartridge::mmc3::MMC3Mapper;
use crate::cartridge::{Mapper, MapperCapabilities};
pub struct Mapper348 {
mmc3: MMC3Mapper,
outer_reg: u8,
}
impl Mapper348 {
const PRG_BANK_SIZE: usize = 0x2000;
const PRG_BANK_MASK: usize = Self::PRG_BANK_SIZE - 1;
const CHR_1K_BANK_SIZE: usize = 0x0400;
const CHR_BANK_MASK: usize = Self::CHR_1K_BANK_SIZE - 1;
const SPECIAL_MODE_FIXED_PRG_BASE: usize = 0x32;
pub fn new(ctx: super::mapper::MapperContext) -> Self {
let prg_rom = ctx.prg_rom;
let chr_rom = ctx.chr_rom;
let mirroring = ctx.mirroring;
Self {
mmc3: MMC3Mapper::new_with_irq_mode(prg_rom, chr_rom, mirroring, false),
outer_reg: 0,
}
}
fn outer_bank_high_bits(&self) -> usize {
(self.outer_reg & 0x0C) as usize
}
fn special_mode(&self) -> bool {
self.outer_bank_high_bits() == 0x0C
}
fn apply_chr_outer_bits(&self, raw_1k_bank: usize) -> usize {
(self.outer_bank_high_bits() << 5) | (raw_1k_bank & 0x7F)
}
fn apply_prg_outer_bits(&self, raw_8k_page: u8) -> usize {
(self.outer_bank_high_bits() << 2) | (usize::from(raw_8k_page) & 0x0F)
}
fn forced_special_mode_prg_bank(&self, source_window_addr: u16) -> usize {
let low_nibble = usize::from(self.mmc3.raw_prg_8k_page_number(source_window_addr)) & 0x0F;
Self::SPECIAL_MODE_FIXED_PRG_BASE | low_nibble
}
fn mapped_chr_bank_and_offset(&self, addr: u16) -> (usize, usize) {
let raw_bank = self.mmc3.raw_chr_1k_bank(addr);
let bank = self.apply_chr_outer_bits(raw_bank);
let offset = (addr as usize) & Self::CHR_BANK_MASK;
(bank, offset)
}
fn mapped_prg_bank_for_addr(&self, addr: u16) -> usize {
if self.special_mode() {
match addr {
0x8000..=0x9FFF => {
self.apply_prg_outer_bits(self.mmc3.raw_prg_8k_page_number(0x8000))
}
0xA000..=0xBFFF => {
self.apply_prg_outer_bits(self.mmc3.raw_prg_8k_page_number(0xA000))
}
0xC000..=0xDFFF => self.forced_special_mode_prg_bank(0x8000),
0xE000..=0xFFFF => self.forced_special_mode_prg_bank(0xA000),
_ => 0,
}
} else {
let raw = self.mmc3.raw_prg_8k_page_number(addr);
self.apply_prg_outer_bits(raw)
}
}
}
impl Mapper for Mapper348 {
fn base(&self) -> &BaseMapper {
&self.mmc3.base
}
fn base_mut(&mut self) -> &mut BaseMapper {
&mut self.mmc3.base
}
fn mmc3_delegate(&self) -> Option<&MMC3Mapper> {
Some(&self.mmc3)
}
fn mmc3_delegate_mut(&mut self) -> Option<&mut MMC3Mapper> {
Some(&mut self.mmc3)
}
fn read_prg(&self, addr: u16) -> u8 {
if !(0x8000..=0xFFFF).contains(&addr) {
return 0;
}
let bank = self.mapped_prg_bank_for_addr(addr);
let offset = (addr as usize) & Self::PRG_BANK_MASK;
self.mmc3.read_prg_at_bank(bank, offset)
}
fn write_prg(&mut self, addr: u16, value: u8) {
if (0x6800..=0x68FF).contains(&addr) {
self.outer_reg = value;
} else if (0x8000..=0xFFFF).contains(&addr) {
self.mmc3.write_prg(addr, value);
}
}
fn mapper_number(&self) -> u16 {
348
}
fn read_chr(&mut self, addr: u16) -> u8 {
let (bank, offset) = self.mapped_chr_bank_and_offset(addr);
self.mmc3.read_chr_1k_at(bank, offset)
}
fn write_chr(&mut self, addr: u16, value: u8) {
let (bank, offset) = self.mapped_chr_bank_and_offset(addr);
self.mmc3.write_chr_1k_at(bank, offset, value);
}
fn registers_snapshot(&self) -> Vec<u8> {
let mut snap = self.mmc3.registers_snapshot();
snap.push(self.outer_reg);
snap
}
fn restore_registers(&mut self, data: &[u8]) {
if let Some((&outer, mmc3_data)) = data.split_last() {
self.outer_reg = outer;
self.mmc3.restore_registers(mmc3_data);
}
}
fn reset(&mut self) {
self.outer_reg = 0;
self.mmc3.reset();
}
fn capabilities(&self) -> MapperCapabilities {
MapperCapabilities {
has_irq: true,
has_chr_banking: true,
has_dynamic_mirroring: true,
has_expansion_audio: false,
max_prg_ram_kb: 0,
prg_bank_size_kb: 8,
chr_bank_size_kb: 1,
..Default::default()
}
}
}
#[cfg(test)]
mod tests {
use crate::cartridge::NametableLayout;
use crate::cartridge::mapper::{Mapper, MapperContext, create_mapper};
use crate::cartridge::test_helpers::banked_data;
const PRG_BANKS_8K: usize = 64;
const CHR_BANKS_1K: usize = 256;
fn make_mapper() -> Box<dyn Mapper> {
create_mapper(MapperContext::new_for_test(
348,
banked_data(8 * 1024, PRG_BANKS_8K),
banked_data(1024, CHR_BANKS_1K),
NametableLayout::Vertical,
))
.expect("Mapper 348 should be implemented")
}
#[test]
fn mapper_348_is_registered_in_factory() {
let result = create_mapper(MapperContext::new_for_test(
348,
banked_data(8 * 1024, PRG_BANKS_8K),
banked_data(1024, CHR_BANKS_1K),
NametableLayout::Vertical,
));
assert!(
result.is_ok(),
"Mapper 348 must be registered in the mapper factory"
);
}
#[test]
fn outer_register_bits_2_3_extend_chr_bank_selection() {
let mut mapper = make_mapper();
mapper.write_prg(0x8000, 0x00);
mapper.write_prg(0x8001, 0x01);
let chr_before = mapper.read_chr(0x0000);
mapper.write_prg(0x6800, 0x04);
let chr_after = mapper.read_chr(0x0000);
assert_ne!(
chr_before, chr_after,
"Writing $6800 with bit2 set should change CHR bank high bits"
);
}
#[test]
fn special_mode_reg_0x0c_forces_upper_prg_windows_from_0x32_or_low_nibble() {
let mut mapper = make_mapper();
mapper.write_prg(0x6800, 0x0C);
mapper.write_prg(0x8000, 0x06);
mapper.write_prg(0x8001, 0x09);
mapper.write_prg(0x8000, 0x07);
mapper.write_prg(0x8001, 0x03);
let bank_low_0 = mapper.read_prg(0x8000);
let bank_low_1 = mapper.read_prg(0xA000);
let bank_high_0 = mapper.read_prg(0xC000);
let bank_high_1 = mapper.read_prg(0xE000);
assert_eq!(bank_high_0, 0x32 | (bank_low_0 & 0x0F));
assert_eq!(bank_high_1, 0x32 | (bank_low_1 & 0x0F));
}
#[test]
fn mirroring_and_capabilities_follow_mmc3_expectations() {
let mut mapper = make_mapper();
mapper.write_prg(0xA000, 0x00);
assert_eq!(mapper.get_mirroring(), NametableLayout::Vertical);
mapper.write_prg(0xA000, 0x01);
assert_eq!(mapper.get_mirroring(), NametableLayout::Horizontal);
let caps = mapper.capabilities();
assert!(caps.has_irq);
assert!(caps.has_chr_banking);
assert!(caps.has_dynamic_mirroring);
assert!(!caps.has_expansion_audio);
}
#[test]
fn writes_to_6000_region_except_6800_68ff_do_not_change_outer_register() {
let mut mapper = make_mapper();
mapper.write_prg(0x6800, 0x00);
mapper.write_prg(0x8000, 0x00);
mapper.write_prg(0x8001, 0x01);
let baseline = mapper.read_chr(0x0000);
mapper.write_prg(0x6000, 0x04);
mapper.write_prg(0x67FF, 0x04);
mapper.write_prg(0x6900, 0x04);
mapper.write_prg(0x7FFF, 0x04);
assert_eq!(mapper.read_chr(0x0000), baseline);
mapper.write_prg(0x6800, 0x04);
assert_ne!(mapper.read_chr(0x0000), baseline);
}
}