76 lines
1.8 KiB
C
76 lines
1.8 KiB
C
//
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// Created by william on 10/15/23.
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//
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#include <assert.h>
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#include "log.h"
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#include "memory.h"
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#include "../include/rom.h"
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#include "cpu.h"
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#define RAM_MAX_ADDR 0x2000
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#define RAM_BANK_SIZE 0x800
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#define PPU_MAX_ADDR 0x4000
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#define PPU_BANK_SIZE 0x8
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#define APU_MAX_ADDR 0x4020
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#define MAX_ADDR 0xffff
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byte ram[RAM_SIZE];
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byte mem_get_byte(address addr) {
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assert(addr <= MAX_ADDR);
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if (addr >= RAM_MAX_ADDR && addr < PPU_MAX_ADDR) {
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byte reg = (addr - RAM_MAX_ADDR) % PPU_BANK_SIZE;
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ppu_sig_read_register(reg);
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}
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return ram[addr];
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}
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byte *mem_get_ptr(address addr) {
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assert(addr <= MAX_ADDR);
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return &ram[addr];
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}
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word mem_get_word(address addr) {
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assert(addr < MAX_ADDR);
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word word = ram[addr];
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word += ram[addr + 1] << 8; // Little endian
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return word;
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}
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void mem_set_byte(address addr, byte byte) {
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assert(addr < MAX_ADDR);
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log_trace("Writing '%02x' to address 0x%04x", byte, addr);
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if (addr < RAM_MAX_ADDR) {
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address init_ram_addr = addr % RAM_BANK_SIZE;
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// The value must also be cloned in the three mirrors
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for (int i = 0; i < 4; i++) {
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address ram_addr = init_ram_addr + RAM_BANK_SIZE * i;
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ram[ram_addr] = byte;
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}
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} else if (addr < PPU_MAX_ADDR) {
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address reg_addr = (addr - RAM_MAX_ADDR) % PPU_BANK_SIZE;
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int bank_count = (PPU_MAX_ADDR - RAM_MAX_ADDR) / PPU_BANK_SIZE;
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for (int i = 0; i < bank_count; i++) {
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address ram_addr = reg_addr + PPU_BANK_SIZE * i + RAM_MAX_ADDR;
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ram[ram_addr] = byte;
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}
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ppu_sig_write_register(reg_addr);
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} else {
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ram[addr] = byte;
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if (addr == PPU_REGISTER_OAM_DMA_ADDR) {
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// Writing to this address triggers an upload to the PPU memory
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cpu_trigger_oam_dma();
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}
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}
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} |