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raxracks 2024-01-27 00:39:48 +13:00
commit b26428cdee
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7
Makefile Normal file
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emulator: emulator.c
gcc emulator.c -o emulator -g -Iinclude
hello: hello.asm
ca65 hello.asm -o hello.o
ld65 hello.o -o hello -C config.cfg
run: hello emulator
./emulator hello

9
config.cfg Normal file
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MEMORY {
RAM: start = $0000, size = $4000, type = rw;
ROM: start = $8000, size = $8000, type = ro;
}
SEGMENTS {
CODE: load = "ROM", type = ro;
DATA: load = "ROM", type = ro;
}

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emulator Executable file
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272
emulator.c Normal file
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#include <stdio.h>
#include <slibs/slibs.h>
#include <stdint.h>
#include <assert.h>
#define NEGATIVE 1 << 7
#define OVERFLOW 1 << 6
#define BREAK 1 << 4
#define DECIMAL 1 << 3
#define INTERRUPT 1 << 2
#define ZERO 1 << 1
#define CARRY 1 << 0
typedef struct {
uint8_t A;
uint8_t X;
uint8_t Y;
uint8_t SP;
uint8_t P;
uint16_t PC;
} CPU;
CPU cpu = { 0 };
uint8_t* memory;
int main(int argc, char** argv) {
assert(argc > 1);
sl_string code = { 0 };
sl_read_file(argv[1], &code);
memory = malloc(sizeof(uint8_t) * 0xffff);
memcpy(memory + 0x8000, code.data, code.size);
for(cpu.PC = 0; cpu.PC < code.size; cpu.PC++) {
uint8_t opcode = code.data[cpu.PC];
uint8_t one = code.data[cpu.PC + 1];
uint8_t two = code.data[cpu.PC + 2];
uint16_t word = (two << 8) | one;
uint8_t h_nib = (opcode >> 4) & 0xF;
uint8_t l_nib = opcode & 0xF;
printf("%d: 0x%02X (h_nib: 0x%X, l_nib: 0x%X)\n", cpu.PC, opcode, h_nib, l_nib);
switch(h_nib) {
case 0x8:
switch(l_nib) {
case 0x1:
printf(" ∟ STA ($%02X, X)\n", one);
memory[memory[one + cpu.X]] = cpu.A;
cpu.PC++;
break;
case 0x5:
printf(" ∟ STA $%02X\n", one);
memory[one] = cpu.A;
cpu.PC++;
break;
case 0x6:
printf(" ∟ STX $%02X\n", one);
memory[one] = cpu.X;
cpu.PC++;
break;
case 0xD:
printf(" ∟ STA $%04X\n", word);
memory[word] = cpu.A;
cpu.PC += 2;
break;
case 0xE:
printf(" ∟ STX $%04X\n", word);
memory[word] = cpu.X;
cpu.PC += 2;
break;
}
break;
case 0x9:
switch(l_nib) {
case 0x1:
printf(" ∟ STA ($%02X), Y\n", one);
memory[memory[one] + cpu.Y] = cpu.A;
cpu.PC++;
break;
case 0x5:
printf(" ∟ STA $%02X, X\n", word);
memory[one + cpu.X] = cpu.A;
cpu.PC++;
break;
case 0x9:
printf(" ∟ STA $%04X, Y\n", word);
memory[word + cpu.Y] = cpu.A;
cpu.PC += 2;
break;
case 0xD:
printf(" ∟ STA $%04X, X\n", word);
memory[word + cpu.X] = cpu.A;
cpu.PC += 2;
break;
}
break;
case 0xA:
switch(l_nib) {
case 0x0:
printf(" ∟ LDY #$%02X\n", one);
cpu.Y = one;
cpu.PC++;
break;
case 0x1:
printf(" ∟ LDA ($%02X, X)\n", one);
cpu.A = memory[memory[one + cpu.X]];
printf("addr: %x val: %x\n", memory[one + cpu.X], cpu.A);
cpu.PC++;
break;
case 0x2:
printf(" ∟ LDX #$%02X\n", one);
cpu.X = one;
cpu.PC++;
break;
case 0x4:
printf(" ∟ LDY $%02X\n", one);
cpu.Y = memory[one];
cpu.PC++;
break;
case 0x5:
printf(" ∟ LDA $%02X\n", one);
cpu.A = memory[one];
cpu.PC++;
break;
case 0x6:
printf(" ∟ LDX $%02X\n", one);
cpu.X = memory[one];
cpu.PC++;
break;
case 0x9:
printf(" ∟ LDA #$%02X\n", one);
cpu.A = one;
cpu.PC++;
break;
case 0xC:
printf(" ∟ LDY $%04X\n", word);
cpu.Y = memory[word];
cpu.PC += 2;
break;
case 0xD:
printf(" ∟ LDA $%04X\n", word);
cpu.A = memory[word];
cpu.PC += 2;
break;
case 0xE:
printf(" ∟ LDX $%04X\n", word);
cpu.X = memory[word];
cpu.PC += 2;
break;
}
break;
case 0xB:
switch(l_nib) {
case 0x1:
printf(" ∟ LDA ($%02X), Y\n", one);
cpu.A = memory[memory[one] + cpu.Y];
printf("addr: %x val: %x\n", memory[one] + cpu.Y, cpu.A);
cpu.PC++;
break;
case 0x4:
printf(" ∟ LDY $%02X, X\n", one);
cpu.Y = memory[one + cpu.X];
printf("addr: %x val: %x\n", one + cpu.X, cpu.Y);
cpu.PC++;
break;
case 0x5:
printf(" ∟ LDA $%02X, X\n", one);
cpu.A = memory[one + cpu.X];
printf("addr: %x val: %x\n", one + cpu.X, cpu.A);
cpu.PC++;
break;
case 0x6:
printf(" ∟ LDX $%02X, Y\n", one);
cpu.X = memory[one + cpu.Y];
printf("addr: %x val: %x\n", one + cpu.Y, cpu.X);
cpu.PC++;
break;
case 0x9:
printf(" ∟ LDA $%04X, Y\n", word);
cpu.A = memory[word + cpu.Y];
printf("addr: %x val: %x\n", word + cpu.Y, cpu.A);
cpu.PC++;
break;
case 0xC:
printf(" ∟ LDY $%04X, X\n", word);
cpu.Y = memory[word + cpu.X];
printf("addr: %x val: %x\n", word + cpu.X, cpu.Y);
cpu.PC += 2;
break;
case 0xD:
printf(" ∟ LDA $%04X, X\n", word);
cpu.A = memory[word + cpu.X];
printf("addr: %x val: %x\n", word + cpu.X, cpu.A);
cpu.PC += 2;
break;
case 0xE:
printf(" ∟ LDX $%04X, Y\n", word);
cpu.X = memory[word + cpu.Y];
printf("addr: %x val: %x\n", word + cpu.Y, cpu.X);
cpu.PC += 2;
break;
}
break;
case 0xC:
switch(l_nib) {
case 0x8:
printf(" ∟ INY\n");
cpu.Y++;
break;
}
break;
case 0xE:
switch(l_nib) {
case 0x6:
printf(" ∟ INC $%02X\n", one);
memory[one]++;
cpu.PC++;
break;
case 0x8:
printf(" ∟ INX\n");
cpu.X++;
break;
case 0xE:
printf(" ∟ INC $%04X\n", word);
memory[word]++;
cpu.PC += 2;
break;
}
break;
case 0xF:
switch(l_nib) {
case 0x6:
printf(" ∟ INC $%02X, X\n", one);
memory[one + cpu.X]++;
cpu.PC++;
break;
case 0xE:
printf(" ∟ INC $%04X, X\n", word);
memory[word + cpu.X]++;
cpu.PC += 2;
break;
}
break;
default:
printf(" ∟ Unimplemented\n");
break;
}
}
printf("CPU State:\n"
"A\t:\t0x%08X\n"
"X\t:\t0x%08X\n"
"Y\t:\t0x%08X\n"
"SP\t:\t0x%08X\n"
"P\t:\t0x%08X\n"
"PC\t:\t0x%016X\n\n"
, cpu.A, cpu.X, cpu.Y, cpu.SP, cpu.P, cpu.PC);
printf("Memory State:\n");
for(int i = 0; i < 0xffff; i++) {
if(memory[i] != 0x0) {
printf("0x%04X: 0x%02X (0b%08b)\n", i, memory[i], memory[i]);
}
}
return 0;
}

40
game.asm Normal file
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.segment "CODE"
.proc main
main:
; Initialize PPU
LDA #%10000000 ; Set the bit 7 to $2000 to use $2000-$2FFF for nametables
STA $2000
LDA #%00011110 ; Enable rendering, enable sprites, and make sure background is visible
STA $2001
; Load sprite data into OAM
LDX #0 ; Initialize X register to zero
LDA SpriteData,X ; Load the first byte of sprite data
STA $0200,X ; Store it in the Object Attribute Memory (OAM)
INX ; Increment X to load the next byte
LDA SpriteData,X ; Load the second byte of sprite data (attributes)
STA $0200,X ; Store it in OAM
INX ; Increment X to load the next byte (X position)
LDA SpriteData,X ; Load the third byte of sprite data (X position)
STA $0200,X ; Store it in OAM
; Infinite loop
forever:
JMP forever
.endproc
.segment "DATA"
SpriteData:
.byte $00 ; Tile index for the sprite
.byte $20 ; Attributes (palette, flipping, etc.)
.byte $80 ; X position of the sprite
; Additional sprite data can be added here
.segment "BSS"
; Define uninitialized memory (if needed)

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hello.asm Normal file
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LDA #10
LDX #$1
STA $20
INC $2000, X

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helloworld.nes Normal file
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39
implemented.txt Normal file
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==== LDA (completed) ====
LDA #
LDA $ (Z)
LDA $ (A)
LDA $, X (Z)
LDA $, X (A)
LDA $, Y (A)
LDA ($, X)
LDA ($), Y
==== LDX (completed) ====
LDX #
LDX $ (Z)
LDX $ (A)
LDX $, Y (Z)
LDX $, Y (A)
==== LDY (completed) ====
LDY #
LDY $ (Z)
LDY $ (A)
LDY $, X (Z)
LDY $, X (A)
==== STA (completed) ====
STA $ (Z)
STA $ (A)
STA $, X (Z)
STA $, X (A)
STA ($, X)
STA ($), Y
==== INC (completed) ====
INX
INY
INC $ (Z)
INC $ (A)
INC $, X (Z)
INC $, X (A)

1
include/slibs Submodule

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Subproject commit 63edb9343b6787883a667b69ece86bde005ab311

6
temp.asm Normal file
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LDA hello, X
INX
LDA hello, X
.DATA
hello: .byte "hello world", 0