Skip to content

Commit

Permalink
Change checks to use byte for opcode, nn, and n
Browse files Browse the repository at this point in the history
  • Loading branch information
@Eggbertx
Eggbertx committed Oct 22, 2024
1 parent 9026eb0 commit dd90e52
Show file tree
Hide file tree
Showing 3 changed files with 70 additions and 69 deletions.
109 changes: 56 additions & 53 deletions src/chip8.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -137,11 +137,13 @@ void stepOut() {
#endif

void _OC8_FASTCALL doCycle() {
uchar x = 0; /* -X-- */
uchar y = 0; /* --Y- */
ushort nnn = 0; /* -nnn */
uchar nn = 0; /* --nn */
uchar n = 0; /* ---n */
ushort romWord = 0;
uchar opcode = 0; /* O--- */
uchar x = 0; /* -X-- */
uchar y = 0; /* --Y- */
ushort nnn = 0; /* -nnn */
uchar nn = 0; /* --nn */
uchar n = 0; /* ---n */

chip8.currentKey = getKey(); /* -1 if no keys are pressed, otherwise the CHIP-8 key value is stored here */

Expand Down Expand Up @@ -169,30 +171,31 @@ void _OC8_FASTCALL doCycle() {
return;
}

chip8.opcode = chip8.memory[chip8.PC++];
nn = chip8.memory[chip8.PC++];
n = nn & 0xFF;
x = chip8.opcode & 0xF;
y = n & 0xF0 >> 4;
nnn = (x << 8) | nn;
romWord = GET_WORD();
chip8.PC += 2;
opcode = OPCODE_INSTRUCTION(romWord);
nnn = OPCODE_NNN(romWord);
nn = OPCODE_NN(romWord);
n = OPCODE_N(romWord);
x = OPCODE_X(romWord);
y = OPCODE_Y(romWord);
chip8.drawFlag = 0;


switch(chip8.opcode & 0xF000) {
case 0x0000:
if(chip8.opcode == 0x0000) {
switch(opcode) {
case 0x00:
if(nn == 0x00) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "SYS %04x", nnn); /* not used for most "modern" ROMs */
#endif
} else if(chip8.opcode == 0x00E0) {
} else if(nn == 0xE0) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
strcpy(currentOpcode, "CLS");
#endif
clearDisplay();
chip8.drawFlag = 1;
} else if(chip8.opcode == 0x00EE) {
} else if(nn == 0xEE) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
strcpy(currentOpcode, "RET");
Expand All @@ -205,7 +208,7 @@ void _OC8_FASTCALL doCycle() {
goto unrecognized_opcode;
}
break;
case 0x1000:
case 0x10:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "JP %#04x", nnn);
Expand All @@ -219,7 +222,7 @@ void _OC8_FASTCALL doCycle() {
}
chip8.PC = nnn;
break;
case 0x2000:
case 0x20:
/* increment SP, put PC on top of stack, set to nnn */
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
Expand All @@ -231,7 +234,7 @@ void _OC8_FASTCALL doCycle() {
chip8.stack[chip8.stackPointer] = chip8.PC;
chip8.PC = nnn;
break;
case 0x3000:
case 0x30:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "SE V%X, #%x", x, nn);
Expand All @@ -240,7 +243,7 @@ void _OC8_FASTCALL doCycle() {
chip8.PC += 2;
}
break;
case 0x4000:
case 0x40:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "SNE V%X, #%x", x, nn);
Expand All @@ -249,7 +252,7 @@ void _OC8_FASTCALL doCycle() {
chip8.PC += 2;
}
break;
case 0x5000:
case 0x50:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "SE V%X, V%X", x, y);
Expand All @@ -258,46 +261,46 @@ void _OC8_FASTCALL doCycle() {
chip8.PC += 2;
}
break;
case 0x6000:
case 0x60:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "LD V%X, #%x", x, nn);
#endif
chip8.V[x] = nn;
break;
case 0x7000:
case 0x70:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "ADD V%X, #%x", x, nn);
#endif
chip8.V[x] += nn;
break;
case 0x8000: {
if(n == 0x0000) {
case 0x80: {
if(n == 0x0) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "LD V%X, V%X", x, y);
#endif
chip8.V[x] = chip8.V[y];
} else if(n == 0x0001) {
} else if(n == 0x1) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "OR V%X, V%X", x, y);
#endif
chip8.V[x] = chip8.V[x] | chip8.V[y];
} else if(n == 0x0002) {
} else if(n == 0x2) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "AND V%X, V%X", x, y);
#endif
chip8.V[x] = chip8.V[x] & chip8.V[y];
} else if(n == 0x0003) {
} else if(n == 0x3) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "XOR V%X, V%X", x, y);
#endif
chip8.V[x] ^= chip8.V[y];
} else if(n == 0x0004) {
} else if(n == 0x4) {
ushort sum = 0;
/*
* Add V[x] and V[y] (lowest 8 bits)
Expand All @@ -310,7 +313,7 @@ void _OC8_FASTCALL doCycle() {
sum = chip8.V[x] + chip8.V[y];
chip8.V[0xF] = sum > 255;
chip8.V[x] = sum & 0xFF;
} else if(n == 0x0005) {
} else if(n == 0x5) {
/*
* Set Vx = Vx - Vy, set VF = NOT borrow.
* If Vx > Vy, then VF is set to 1, otherwise 0.
Expand All @@ -322,7 +325,7 @@ void _OC8_FASTCALL doCycle() {
#endif
chip8.V[0xF] = chip8.V[x] > chip8.V[y];
chip8.V[x] -= chip8.V[y];
} else if(n == 0x0006) {
} else if(n == 0x6) {
/*
* If the least-significant bit of Vx is 1, then VF is set to 1, otherwise 0.
* Then Vx is divided by 2.
Expand All @@ -334,7 +337,7 @@ void _OC8_FASTCALL doCycle() {
chip8.V[0xF] = (chip8.V[x] & 1);
chip8.V[x] /= 2;
/* chip8.V[x] = chip8.V[x] >> 1; */
} else if(n == 0x0007) {
} else if(n == 0x7) {
/*
* If Vy > Vx, then VF is set to 1, otherwise 0.
* Then Vx is subtracted from Vy, and the results stored in Vx.
Expand All @@ -344,7 +347,7 @@ void _OC8_FASTCALL doCycle() {
#endif
chip8.V[0xF] = chip8.V[y] > chip8.V[x];
chip8.V[x] = chip8.V[y] - chip8.V[x];
} else if(n == 0x000E) {
} else if(n == 0xE) {
/*
* If the most-significant bit of Vx is 1, then VF is set to 1, otherwise to 0.
* Then Vx is multiplied by 2.
Expand All @@ -360,29 +363,29 @@ void _OC8_FASTCALL doCycle() {
}
}
break;
case 0x9000:
case 0x90:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "SNE V%X, V%X", x, y);
#endif
if(chip8.V[x] != chip8.V[y])
chip8.PC += 2;
break;
case 0xA000:
case 0xA0:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "LD I, %#04x", nnn);
#endif
chip8.I = nnn;
break;
case 0xB000:
case 0xB0:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "JP V0, %#04x", nnn);
#endif
chip8.PC = nnn + chip8.V[0];
break;
case 0xC000: {
case 0xC0: {
uchar rnd;
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
Expand All @@ -392,36 +395,36 @@ void _OC8_FASTCALL doCycle() {
chip8.V[x] = rnd & nn;
break;
}
case 0xD000:
case 0xD0:
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "DRW %X, %X, %X", x, y, n);
#endif
drawSprite(x, y, n);
break;
case 0xE000:
if(nn == 0x009E) {
case 0xE0:
if(nn == 0x9E) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "SKP V%X", x);
#endif
if(isPressed(chip8.V[x])) chip8.PC += 2;
} else if(nn == 0x00A1) {
} else if(nn == 0xA1) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "SKNP V%X", x);
#endif
if(!isPressed(chip8.V[x])) chip8.PC += 2;
}
break;
case 0xF000: {
if(nn == 0x0007) {
case 0xF0: {
if(nn == 0x7) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "LD V%X, DT", x);
#endif
chip8.V[x] = chip8.delayTimer;
} else if(nn == 0x000A) {
} else if(nn == 0xA) {
int key = 0xFF;
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
Expand All @@ -431,23 +434,23 @@ void _OC8_FASTCALL doCycle() {
key = getKey();
} while(key == 0xFF);
chip8.V[x] = key;
} else if(nn == 0x0015) {
} else if(nn == 0x15) {
chip8.delayTimer = chip8.V[x];
} else if(nn == 0x0018) {
} else if(nn == 0x18) {
chip8.soundTimer = chip8.V[x];
} else if(nn == 0x001E) {
} else if(nn == 0x1E) {
chip8.I += chip8.V[x];
} else if(nn == 0x0029) {
} else if(nn == 0x29) {
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
sprintf(currentOpcode, "LD F, V%X", x);
#endif
chip8.I = chip8.V[x] * 5;
} else if(nn == 0x0033) {
} else if(nn == 0x33) {
chip8.memory[chip8.I+0] = chip8.V[x] / 100;
chip8.memory[chip8.I+1] = (chip8.V[x] / 10) % 10;
chip8.memory[chip8.I+2] = chip8.V[x] % 10;
} else if(nn == 0x0055) {
} else if(nn == 0x55) {
ushort i;
#ifdef DEBUG_KEYS
CLEAR_CURENT_OPCODE();
Expand All @@ -456,7 +459,7 @@ void _OC8_FASTCALL doCycle() {
for(i = 0; i <= x; i++) {
chip8.memory[chip8.I + i] = chip8.V[i];
}
} else if(nn == 0x0065) {
} else if(nn == 0x65) {
ushort i;
for(i = 0; i <= x; i++) {
chip8.V[i] = chip8.memory[chip8.I + i];
Expand All @@ -472,7 +475,7 @@ void _OC8_FASTCALL doCycle() {

unrecognized_opcode:
cleanup();
printf("Error: Unrecognized opcode: %04x at %04x\n", chip8.opcode, chip8.PC);
printf("Error: Unrecognized opcode: %04x at %04x\n", romWord, chip8.PC);
printStatus();
chip8.status = STATUS_ERROR;
return;
Expand Down
15 changes: 7 additions & 8 deletions src/chip8.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,13 +33,13 @@
#define STATUS_PAUSED 2
#define STATUS_ERROR 4

#define OPCODE() (chip8.memory[chip8.PC] << 8) | (chip8.memory[chip8.PC + 1])
#define OPCODE_INSTRUCTION() (chip8.opcode & 0xF000) >> 12
#define OPCODE_X() (chip8.opcode & 0x0F00) >> 8
#define OPCODE_Y() (chip8.opcode & 0x00F0) >> 4
#define OPCODE_NNN() chip8.opcode & 0x0FFF
#define OPCODE_NN() chip8.opcode & 0xFF
#define OPCODE_N() chip8.opcode & 0xF
#define GET_WORD() (chip8.memory[chip8.PC] << 8) | (chip8.memory[chip8.PC + 1])
#define OPCODE_INSTRUCTION(w) (w & 0xF000) >> 8
#define OPCODE_X(w) (w & 0x0F00) >> 8
#define OPCODE_Y(w) (w & 0x00F0) >> 4
#define OPCODE_NNN(w) w & 0x0FFF
#define OPCODE_NN(w) w & 0xFF
#define OPCODE_N(w) w & 0xF

#ifdef __CC65__
#define _OC8_FASTCALL __fastcall__
Expand All @@ -64,7 +64,6 @@ struct Chip8 {
uchar stackPointer;
uchar memory[CHIP8_MEMORY]; /* 4 KB, font located at 0x8110 */

uchar opcode;
uchar key[16];
schar currentKey;
uchar screen[SCREEN_MEMORY]; /* All drawings are done in XOR mode. */
Expand Down
15 changes: 7 additions & 8 deletions src/tests/chip8_test.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,14 +64,13 @@ TEST_F(Chip8Test, TestMacros) {
loadROM("games/macros", rom_macros);
ASSERT_EQ(chip8.romSize, rom_macros_size);
ASSERT_EQ(chip8.PC, ROM_START_ADDR);
ushort op = OPCODE();
chip8.opcode = op;
ASSERT_EQ(op, 0x0123);
ASSERT_EQ(OPCODE_N(), 3);
ASSERT_EQ(OPCODE_NN(), 0x23);
ASSERT_EQ(OPCODE_NNN(), 0x123);
ASSERT_EQ(OPCODE_X(), 1);
ASSERT_EQ(OPCODE_Y(), 2);
ushort romWord = GET_WORD();;
ASSERT_EQ(romWord, 0x0123);
ASSERT_EQ(OPCODE_N(romWord), 3);
ASSERT_EQ(OPCODE_NN(romWord), 0x23);
ASSERT_EQ(OPCODE_NNN(romWord), 0x123);
ASSERT_EQ(OPCODE_X(romWord), 1);
ASSERT_EQ(OPCODE_Y(romWord), 2);
}

TEST_F(Chip8Test, TestSize) {
Expand Down

0 comments on commit dd90e52

Please sign in to comment.