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129 lines (105 loc) · 3.62 KB
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/*
olc::NES - Mapper 000 - NROM
"Thanks Dad for believing computers were gonna be a big deal..." - javidx9
License (OLC-3)
~~~~~~~~~~~~~~~
Copyright 2018-2019 OneLoneCoder.com
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions or derivations of source code must retain the above
copyright notice, this list of conditions and the following disclaimer.
2. Redistributions or derivative works in binary form must reproduce
the above copyright notice. This list of conditions and the following
disclaimer must be reproduced in the documentation and/or other
materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Relevant Video: https://youtu.be/xdzOvpYPmGE
Links
~~~~~
YouTube: https://www.youtube.com/javidx9
https://www.youtube.com/javidx9extra
Discord: https://discord.gg/WhwHUMV
Twitter: https://www.twitter.com/javidx9
Twitch: https://www.twitch.tv/javidx9
GitHub: https://www.github.com/onelonecoder
Patreon: https://www.patreon.com/javidx9
Homepage: https://www.onelonecoder.com
Author
~~~~~~
David Barr, aka javidx9, �OneLoneCoder 2019
*/
#include "Mapper_000.h"
Mapper_000::Mapper_000(uint8_t prgBanks, uint8_t chrBanks) : Mapper(prgBanks, chrBanks)
{
reset();
}
Mapper_000::~Mapper_000()
{
}
void Mapper_000::reset()
{
}
bool Mapper_000::cpuMapRead(uint16_t addr, uint32_t &mapped_addr)
{
// if PRGROM is 16KB
// CPU Address Bus PRG ROM
// 0x8000 -> 0xBFFF: Map 0x0000 -> 0x3FFF
// 0xC000 -> 0xFFFF: Mirror 0x0000 -> 0x3FFF
// if PRGROM is 32KB
// CPU Address Bus PRG ROM
// 0x8000 -> 0xFFFF: Map 0x0000 -> 0x7FFF
if (addr >= 0x8000 && addr <= 0xFFFF)
{
mapped_addr = addr & (nPRGBanks > 1 ? 0x7FFF : 0x3FFF);
return true;
}
return false;
}
bool Mapper_000::cpuMapWrite(uint16_t addr, uint32_t &mapped_addr)
{
if (addr >= 0x8000 && addr <= 0xFFFF)
{
mapped_addr = addr & (nPRGBanks > 1 ? 0x7FFF : 0x3FFF);
return true;
}
return false;
}
bool Mapper_000::ppuMapRead(uint16_t addr, uint32_t &mapped_addr)
{
// There is no mapping required for PPU
// PPU Address Bus CHR ROM
// 0x0000 -> 0x1FFF: Map 0x0000 -> 0x1FFF
if (addr >= 0x0000 && addr <= 0x1FFF)
{
mapped_addr = addr;
return true;
}
return false;
}
bool Mapper_000::ppuMapWrite(uint16_t addr, uint32_t &mapped_addr)
{
if (addr >= 0x0000 && addr <= 0x1FFF)
{
if (nCHRBanks == 0)
{
// Treat as RAM
mapped_addr = addr;
return true;
}
}
return false;
}