commit 024662694be4fddbe0ccbdd0631a14406d9c2497
Author: Léo Villeveygoux <leo.villeveygoux@u-bordeaux.fr>
Date: Fri, 30 Nov 2018 19:18:59 +0100
initial commit: base emulator
Working stuff:
* all 36 base CHIP-8 instruction implemented
* loading file argument at address 0x200
* basic terminal diplay
* fixed 1ms sleep between instructions
Thing probably needed to play basic games:
* input handling
* frequency tuning
* sound
* graphic display, debug outputs, input config, pause, save, shaders, VR, …
Diffstat:
| A | chip8.c | | | 382 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
1 file changed, 382 insertions(+), 0 deletions(-)
diff --git a/chip8.c b/chip8.c
@@ -0,0 +1,382 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+
+unsigned char RAM[0x1000];
+
+unsigned char V[16];
+unsigned short I;
+
+unsigned char DT;
+unsigned char ST;
+
+unsigned short PC=0x200;
+unsigned char SP;
+
+unsigned short STACK[16];
+
+unsigned short KEYBOARD;
+
+unsigned char SCREEN[256];
+
+#define CHAR_SPRITES_OFFSET 0x100
+char char_sprites[80] = {
+ /* Source: Cowgod's Chip-8 Technical Reference */
+ /* 0 */
+ 0xF0,
+ 0x90,
+ 0x90,
+ 0x90,
+ 0xF0,
+ /* 1 */
+ 0x20,
+ 0x60,
+ 0x20,
+ 0x20,
+ 0x70,
+ /* 2 */
+ 0xF0,
+ 0x10,
+ 0xF0,
+ 0x80,
+ 0xF0,
+ /* 3 */
+ 0xF0,
+ 0x10,
+ 0xF0,
+ 0x10,
+ 0xF0,
+ /* 4 */
+ 0x90,
+ 0x90,
+ 0xF0,
+ 0x10,
+ 0x10,
+ /* 5 */
+ 0xF0,
+ 0x80,
+ 0xF0,
+ 0x10,
+ 0xF0,
+ /* 6 */
+ 0xF0,
+ 0x80,
+ 0xF0,
+ 0x90,
+ 0xF0,
+ /* 7 */
+ 0xF0,
+ 0x10,
+ 0x20,
+ 0x40,
+ 0x40,
+ /* 8 */
+ 0xF0,
+ 0x90,
+ 0xF0,
+ 0x90,
+ 0xF0,
+ /* 9 */
+ 0xF0,
+ 0x90,
+ 0xF0,
+ 0x10,
+ 0xF0,
+ /* A */
+ 0xF0,
+ 0x90,
+ 0xF0,
+ 0x90,
+ 0x90,
+ /* B */
+ 0xE0,
+ 0x90,
+ 0xE0,
+ 0x90,
+ 0xE0,
+ /* C */
+ 0xF0,
+ 0x80,
+ 0x80,
+ 0x80,
+ 0xF0,
+ /* D */
+ 0xE0,
+ 0x90,
+ 0x90,
+ 0x90,
+ 0xE0,
+ /* E */
+ 0xF0,
+ 0x80,
+ 0xF0,
+ 0x80,
+ 0xF0,
+ /* F */
+ 0xF0,
+ 0x80,
+ 0xF0,
+ 0x80,
+ 0x80,
+};
+
+/* instructions are a 2 char array */
+
+#define I_SHORT(instr) (short)((instr)[0]<<8u | (instr)[1])
+#define I_CLASS(instr) ((instr)[0]>>4u)
+#define I_NNN(instr) ((((instr)[0]&15u)<<8u) | (instr)[1])
+#define I_ADDR(instr) I_NNN(instr)
+#define I_NN(instr) ((instr)[1])
+#define I_KK(instr) I_NN(instr)
+#define I_N(instr) ((instr)[1]&15u)
+#define I_NIBBLE(instr) I_N(inst)
+#define I_X(instr) ((instr)[0]&15u)
+#define I_Y(instr) ((instr)[1]>>4u)
+
+/*XXX:debug*/
+void display();
+
+void step(){
+ unsigned char instr[2] = {RAM[PC], RAM[PC+1]};
+ /* TODO: debug: print state */
+ PC+=2;
+ switch(I_CLASS(instr)){
+ case 0:
+ switch(I_SHORT(instr)){
+ case 0x00E0: /* clear screen */
+ for(int i=0 ; i<256 ; i++)
+ SCREEN[i] = 0;
+ break;
+ case 0x00EE: /* return from a subroutine */
+ if(SP)
+ PC=STACK[--SP];
+ break;
+ default: /*legacy instr*/
+ /*TODO: warn*/
+ break;
+ }
+ break;
+ case 1: /* jump */
+ PC=I_ADDR(instr);
+ break;
+ case 2: /* call a subroutine */
+ STACK[SP++] = PC;
+ PC=I_ADDR(instr);
+ break;
+ case 3:
+ if(V[I_X(instr)] == I_NN(instr))
+ PC+=2;
+ break;
+ case 4:
+ if(V[I_X(instr)] != I_NN(instr))
+ PC+=2;
+ break;
+ case 5:
+ if(V[I_X(instr)] == V[I_Y(instr)])
+ PC+=2;
+ break;
+ case 6:
+ V[I_X(instr)] = I_NN(instr);
+ break;
+ case 7:
+ V[I_X(instr)] += I_NN(instr);
+ break;
+ case 8:
+ switch(I_N(instr)){
+ case 0:
+ V[I_X(instr)] = V[I_Y(instr)];
+ break;
+ case 1:
+ V[I_X(instr)] |= V[I_Y(instr)];
+ break;
+ case 2:
+ V[I_X(instr)] &= V[I_Y(instr)];
+ break;
+ case 3:
+ V[I_X(instr)] ^= V[I_Y(instr)];
+ break;
+ case 4:
+ V[0xf] = V[I_X(instr)] + V[I_Y(instr)] > 0xff ? 1 : 0;
+ V[I_X(instr)] += V[I_Y(instr)];
+ break;
+ case 5:
+ V[0xf] = V[I_X(instr)] > V[I_Y(instr)] ? 1 : 0;
+ V[I_X(instr)] -= V[I_Y(instr)];
+ break;
+ case 6:
+ V[0xf] = V[I_X(instr)]&1u;
+ V[I_X(instr)] >>= 1u;
+ break;
+ case 7:
+ V[0xf] = V[I_X(instr)] < V[I_Y(instr)] ? 1 : 0;
+ V[I_X(instr)] = V[I_Y(instr)] - V[I_X(instr)] ;
+ break;
+ case 0xE:
+ V[0xf] = V[I_X(instr)]>>7u;
+ V[I_X(instr)] <<= 1u;
+ break;
+
+
+
+ default: /*unknown instruction*/
+ /*TODO: warn*/
+ break;
+ }
+ break;
+ case 9:
+ if(V[I_X(instr)] != V[I_Y(instr)])
+ PC+=2;
+ break;
+ case 0xA:
+ I=I_ADDR(instr);
+ break;
+ case 0xB:
+ PC = I_ADDR(instr) + V[0];
+ break;
+ case 0xC:
+ V[I_X(instr)] = rand() & I_NN(instr);
+ break;
+ case 0xD: /*display*/
+ /*TODO:check OOB coords*/
+ /*assert(Vx in [0;63], Vy in [0;31]), Vy+nible in [0;31]*/
+ V[0xf] = 0;
+ unsigned char x = V[I_X(instr)];
+ unsigned char y = V[I_Y(instr)];
+ unsigned char shift = x%8;
+
+ for(int i=0;i<I_N(instr);i++){
+ unsigned char *screen_tile = &SCREEN[(y+i)*8+x/8];
+ unsigned char sprite_tile = RAM[I+i]>>shift;
+ V[0xf] |= *screen_tile & sprite_tile ? 1:0;
+ *screen_tile ^= sprite_tile;
+ if(shift){
+ screen_tile = &SCREEN[(y+i)*8+(x/8+1)%8];
+ sprite_tile = RAM[I+i]<<(8u-shift);
+ V[0xf] |= *screen_tile & sprite_tile ? 1:0;
+ *screen_tile ^= sprite_tile;
+ }
+ }
+ /*XXX:debug*/
+ display();
+ //usleep(500000);
+ break;
+ case 0xE:
+ switch(I_NN(instr)){
+ case 0x9E:
+ if(KEYBOARD & 1<<(V[I_X(instr)]))
+ PC+=2;
+ break;
+ case 0xA1:
+ if(!(KEYBOARD & 1<<(V[I_X(instr)])))
+ PC+=2;
+ break;
+ default: /*unknown instruction*/
+ /*TODO: warn*/
+ break;
+
+ }
+ break;
+ case 0xF:
+ switch(I_NN(instr)){
+ case 0x07:
+ V[I_X(instr)]=DT;
+ break;
+ case 0x0A:
+ if(!KEYBOARD)
+ PC-=2;
+ else {
+ V[I_X(instr)]=0;
+ for(unsigned char k=KEYBOARD;!(k&1);k>>=1)
+ V[I_X(instr)]++;
+ }
+ break;
+ case 0x15:
+ DT=V[I_X(instr)];
+ break;
+ case 0x18:
+ ST=V[I_X(instr)];
+ break;
+ case 0x1E:
+ I+=V[I_X(instr)];
+ break;
+ case 0x29:
+ /*TODO: warn OOB*/
+ if(V[I_X(instr)]<=0xF)
+ I = CHAR_SPRITES_OFFSET + 5*V[I_X(instr)];
+ break;
+ case 0x33:
+ RAM[I+2] = V[I_X(instr)]%10;
+ RAM[I+1] = (V[I_X(instr)]/10)%10;
+ RAM[I] = (V[I_X(instr)]/100)%10;
+ break;
+ case 0x55:
+ for(int i=0 ; i<I_X(instr) ; i++)
+ RAM[I+i] = V[i];
+ break;
+ case 0x65:
+ for(int i=0 ; i<I_X(instr) ; i++)
+ V[i] = RAM[I+i];
+ break;
+ default: /*unknown instruction*/
+ /*TODO: warn*/
+ break;
+ }
+ break;
+ default: /*unknown instr*/
+ /*TODO: warn*/
+ break;
+ }
+
+}
+
+void display(){
+ printf("\033[H");
+ for(int y=0 ; y<32 ; y++){
+ for(int xc=0 ; xc<8 ; xc++){
+ for(int xb=7 ; xb>=0 ; xb--){
+ printf("%s",SCREEN[y*8+xc]&1<<xb ? "█":" ");
+ }
+ }
+ printf("\n");
+ }
+}
+
+int main(int argc, char **argv){
+
+ /* Set up char sprites */
+ for(int i=0 ; i<sizeof(char_sprites) ; i++)
+ RAM[CHAR_SPRITES_OFFSET+i] = char_sprites[i];
+
+ /* Load ROM */
+ if(argc<2)
+ return 1;
+ FILE *rom=fopen(argv[1], "r");
+ if(!rom)
+ return 2;
+ fread(RAM+0x200,1,0x1000-0x200,rom);
+ if(ferror(rom))
+ return 3;
+ fclose(rom);
+
+ /*TODO: init more stuff: graphics, input, sound, timer*/
+
+ /* Let's go */
+ for(int i=0 ; 1 ; i++){
+ step();
+ /*XXX:debug*/
+ /*TODO: other stuff*/
+ //display();
+ nanosleep(&(struct timespec){0,1000000},NULL);
+ if(!(i%16)){
+ //display();
+ if(DT)
+ DT--;
+ if(ST)
+ ST--;
+ }
+ printf("i=%5d, DT=%3d \r", i, (int)DT);
+ }
+
+ return 0;
+}
