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#include "chip8.h"
uint16_t opcode; // 2 byte opcode
uint8_t key[KEY_SIZE]; // hex key input
uint32_t video[WIDTH*HEIGHT]; // video memory TODO: video should be 8 bit not 32
uint8_t V[16]; // registers - 0x0 to 0xF
uint16_t I; // special I register, stores addresses
uint16_t PC; // program counter
uint8_t SP; // stack pointer
uint16_t stack[STACK_SIZE]; // stack, for address storage when using subroutines, maximum of 16 levels of nested subroutines
uint8_t memory[MEMORY_SIZE]; // 4KB of program memory
int draw_flag; // draw flag, when 1 the screen will be drawn
uint8_t delay_timer; // delay timer, decremented by one at 60hz, at 0 do nothing
uint8_t sound_timer; // sound timer, decremented by one at 60hz, while it is > 0 a beep is played
/* 0 - F hexidecimal font as required by the chip8 spec */
uint8_t chip8_fontset[80] =
{
0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
0x20, 0x60, 0x20, 0x20, 0x70, // 1
0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
0x90, 0x90, 0xF0, 0x10, 0x10, // 4
0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
0xF0, 0x10, 0x20, 0x40, 0x40, // 7
0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
0xF0, 0x90, 0xF0, 0x90, 0x90, // A
0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
0xF0, 0x80, 0x80, 0x80, 0xF0, // C
0xE0, 0x90, 0x90, 0x90, 0xE0, // D
0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
0xF0, 0x80, 0xF0, 0x80, 0x80 // F
};
int
load_rom(char *rom)
{
int ret = 1;
printf("loading rom %s..\n", rom);
FILE *romfile;
romfile = fopen(rom, "rb");
if (romfile == NULL)
{
fprintf(stderr, "cannot read rom %s: %s\n", rom, strerror(errno));
ret = 0;
}
/* read a maximum of MAX_ROM_SIZE bytes into memory starting after the reserved memory */
fread(&memory[0x200], 1, MAX_ROM_SIZE, romfile);
fclose(romfile);
return ret;
}
void
chip8_init()
{
/* clear everything and set sane defaults */
memset(key, 0, sizeof(uint8_t) * 15);
memset(video, 0, (WIDTH*HEIGHT) * sizeof(uint32_t));
memset(V, 0, sizeof(uint8_t) * 16);
memset(stack, 0, (STACK_SIZE) * sizeof(uint16_t));
memset(memory, 0, sizeof(uint8_t) * MEMORY_SIZE);
PC = 0x200; // set program counter to where roms are stored
opcode = 0;
I = 0;
SP = 0;
draw_flag = 1; // draw by default i guess
delay_timer = 0;
sound_timer = 0;
srand(time(NULL)); // seed rng
/* load font into memory at 0x00: we have 0x00 to 0x1FF free for anything we want */
//TODO: add whole alphabet, then can write a rom to write strings or something
for (uint8_t i = 0; i < 80; i++)
{
memory[0x0 + i] = chip8_fontset[i];
}
}
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