#include #include #include #include #include #include #define SCALE 4 #define SCREEN_WIDTH 280 #define SCREEN_HEIGHT 192 #define SCREEN_REFRESH_EVERY_CYCLES 10000 #define CARRY 0x01 #define ZERO 0x02 #define INTERRUPT_DISABLE 0x04 #define DECIMAL_MODE 0x08 #define INTERRUPT_VECTORING 0x10 #define OVERFLOW 0x40 #define NEGATIVE 0x80 Display *dsp; Window win; GC gc; unsigned int white, black; Atom wmDelete; XEvent evt; KeyCode keyQ; uint8_t show_screen = 0; uint8_t show_log = 1; int init_display() { dsp = XOpenDisplay(NULL); if (!dsp) return 1; int screen = DefaultScreen(dsp); white = WhitePixel(dsp, screen); black = BlackPixel(dsp, screen); win = XCreateSimpleWindow(dsp, DefaultRootWindow(dsp), 0, 0, SCREEN_WIDTH * SCALE, SCREEN_HEIGHT * SCALE, 0, black, black ); wmDelete = XInternAtom(dsp, "WM_DELETE_WINDOW", True); XSetWMProtocols(dsp, win, &wmDelete, 1); gc = XCreateGC(dsp, win, 0, NULL); // XSetForeground(dsp, gc, white); long eventMask = StructureNotifyMask; eventMask |= ButtonPressMask|ButtonReleaseMask|KeyPressMask|KeyReleaseMask; XSelectInput(dsp, win, eventMask); keyQ = XKeysymToKeycode(dsp, XStringToKeysym("Q")); XMapWindow(dsp, win); // wait until window appears do { XNextEvent(dsp,&evt); } while (evt.type != MapNotify); } uint16_t yoffset[192] = { 0x0000, 0x0400, 0x0800, 0x0c00, 0x1000, 0x1400, 0x1800, 0x1c00, 0x0080, 0x0480, 0x0880, 0x0c80, 0x1080, 0x1480, 0x1880, 0x1c80, 0x0100, 0x0500, 0x0900, 0x0d00, 0x1100, 0x1500, 0x1900, 0x1d00, 0x0180, 0x0580, 0x0980, 0x0d80, 0x1180, 0x1580, 0x1980, 0x1d80, 0x0200, 0x0600, 0x0a00, 0x0e00, 0x1200, 0x1600, 0x1a00, 0x1e00, 0x0280, 0x0680, 0x0a80, 0x0e80, 0x1280, 0x1680, 0x1a80, 0x1e80, 0x0300, 0x0700, 0x0b00, 0x0f00, 0x1300, 0x1700, 0x1b00, 0x1f00, 0x0380, 0x0780, 0x0b80, 0x0f80, 0x1380, 0x1780, 0x1b80, 0x1f80, 0x0028, 0x0428, 0x0828, 0x0c28, 0x1028, 0x1428, 0x1828, 0x1c28, 0x00a8, 0x04a8, 0x08a8, 0x0ca8, 0x10a8, 0x14a8, 0x18a8, 0x1ca8, 0x0128, 0x0528, 0x0928, 0x0d28, 0x1128, 0x1528, 0x1928, 0x1d28, 0x01a8, 0x05a8, 0x09a8, 0x0da8, 0x11a8, 0x15a8, 0x19a8, 0x1da8, 0x0228, 0x0628, 0x0a28, 0x0e28, 0x1228, 0x1628, 0x1a28, 0x1e28, 0x02a8, 0x06a8, 0x0aa8, 0x0ea8, 0x12a8, 0x16a8, 0x1aa8, 0x1ea8, 0x0328, 0x0728, 0x0b28, 0x0f28, 0x1328, 0x1728, 0x1b28, 0x1f28, 0x03a8, 0x07a8, 0x0ba8, 0x0fa8, 0x13a8, 0x17a8, 0x1ba8, 0x1fa8, 0x0050, 0x0450, 0x0850, 0x0c50, 0x1050, 0x1450, 0x1850, 0x1c50, 0x00d0, 0x04d0, 0x08d0, 0x0cd0, 0x10d0, 0x14d0, 0x18d0, 0x1cd0, 0x0150, 0x0550, 0x0950, 0x0d50, 0x1150, 0x1550, 0x1950, 0x1d50, 0x01d0, 0x05d0, 0x09d0, 0x0dd0, 0x11d0, 0x15d0, 0x19d0, 0x1dd0, 0x0250, 0x0650, 0x0a50, 0x0e50, 0x1250, 0x1650, 0x1a50, 0x1e50, 0x02d0, 0x06d0, 0x0ad0, 0x0ed0, 0x12d0, 0x16d0, 0x1ad0, 0x1ed0, 0x0350, 0x0750, 0x0b50, 0x0f50, 0x1350, 0x1750, 0x1b50, 0x1f50, 0x03d0, 0x07d0, 0x0bd0, 0x0fd0, 0x13d0, 0x17d0, 0x1bd0, 0x1fd0 }; typedef struct { uint16_t ip; uint8_t sp; uint32_t total_cycles; uint8_t a, x, y, flags; } r_cpu; void init_cpu(r_cpu* cpu) { cpu->ip = 0; cpu->sp = 0xff; cpu->total_cycles = 0; cpu->a = 0; cpu->x = 0; cpu->y = 0; cpu->flags = 0x20; // bit 5 is always set } uint8_t ram[0x10000]; r_cpu cpu; void load(char* path, uint16_t offset) { uint8_t buffer[0x10000]; size_t size; FILE* f; f = fopen(path, "rw"); if (!f) { printf("Error reading file: %s\n", path); exit(1); } size = fread(buffer, 1, 0x10000, f); printf("Read 0x%04x bytes from %s, saved to 0x%04x.\n", (int)size, path, offset); memcpy(ram + offset, buffer, size); fclose(f); } uint8_t rip8() { return ram[cpu.ip++]; } uint16_t rip16() { uint16_t result = rip8(); result |= ((uint16_t)rip8()) << 8; return result; } uint8_t read8(uint16_t address) { return ram[address]; } uint16_t read16(uint16_t address) { uint16_t result = read8(address); result |= ((uint16_t)read8(address + 1)) << 8; return result; } void write8(uint16_t address, uint8_t value) { ram[address] = value; } void write16(uint16_t address, uint16_t value) { ram[address] = value & 0xff; ram[address + 1] = (value >> 8) & 0xff; } void push(uint8_t value) { if (cpu.sp == 0) { printf("Stack overflow!\n"); exit(1); } ram[(uint16_t)cpu.sp + 0x100] = value; cpu.sp--; } uint8_t pop() { if (cpu.sp == 0xff) { printf("Stack underrun!\n"); exit(1); } cpu.sp++; return ram[(uint16_t)cpu.sp + 0x100]; } void set_flag(int which, int value) { // TODO: Implement decimal mode (BCD) // if ((which == DECIMAL_MODE) && value) // { // printf("Decimal flag not implemented yet!"); // exit(1); // } cpu.flags &= ~which; if (value) cpu.flags |= which; } void update_zero_and_negative_flags(uint8_t value) { set_flag(ZERO, value == 0); set_flag(NEGATIVE, value & 0x80); } uint8_t test_flag(int which) { return ((cpu.flags & which) == 0) ? 0 : 1; } void cmp(uint8_t a, uint8_t b) { set_flag(CARRY, a >= b); set_flag(ZERO, a == b); set_flag(NEGATIVE, (a - b) & 0x80); } uint8_t rol(uint8_t x) { uint8_t old_carry = test_flag(CARRY); set_flag(CARRY, x & 0x80); x <<= 1; if (old_carry) x |= 1; return x; } uint8_t ror(uint8_t x) { uint8_t old_carry = test_flag(CARRY); set_flag(CARRY, x & 1); x >>= 1; if (old_carry) x |= 0x80; return x; } void sbc(uint8_t value) { uint8_t new_carry = (value > cpu.a) ? 1 : 0; cpu.a -= value; if (!test_flag(CARRY)) { if (1 > cpu.a) new_carry = 1; cpu.a -= 1; } update_zero_and_negative_flags(cpu.a); set_flag(CARRY, !new_carry); } void adc(uint8_t value) { uint16_t t16 = cpu.a + value + (test_flag(CARRY) ? 1 : 0); set_flag(CARRY, t16 > 0xff); cpu.a = t16 & 0xff; update_zero_and_negative_flags(cpu.a); } #define OPCODES \ _(ADC) _(AND) _(ASL) _(BCC) _(BCS) _(BEQ) _(BIT) _(BMI) _(BNE) _(BPL) _(BRK) _(BVC) \ _(BVS) _(CLC) _(CLD) _(CLI) _(CLV) _(CMP) _(CPX) _(CPY) _(DEC) _(DEX) _(DEY) _(EOR) \ _(INC) _(INX) _(INY) _(JMP) _(JSR) _(LDA) _(LDX) _(LDY) _(LSR) _(NOP) _(ORA) _(PHA) \ _(PHP) _(PLA) _(PLP) _(ROL) _(ROR) _(RTI) _(RTS) _(SBC) _(SEC) _(SED) _(SEI) _(STA) \ _(STX) _(STY) _(TAX) _(TAY) _(TSX) _(TXA) _(TXS) _(TYA) \ _(BRA) _(PHX) _(PHY) _(PLX) _(PLY) _(STZ) _(TRB) _(TSB) _(DEA) _(INA) #define _(x) x, typedef enum { NO_OPCODE = -1, OPCODES } r_opcode; #undef _ #define _(x) #x, const char* const OPCODE_STRINGS[] = { OPCODES }; #undef _ #define ADDRESSING_MODES \ _(accumulator) \ _(immediate) \ _(implied) \ _(relative) \ _(absolute) \ _(zero_page) \ _(zero_page_indirect) \ _(indirect) /* JMP only */ \ _(zero_page_x) \ _(zero_page_y) \ _(absolute_x) /* +1 for page overflow */ \ _(absolute_y) /* +1 for page overflow */ \ _(indexed_indirect_x) \ _(indirect_indexed_y) /* +1 for page overflow */ #define _(x) x, typedef enum { NO_ADDRESSING_MODE = -1, ADDRESSING_MODES } r_addressing_mode; #undef _ #define _(x) #x, const char* const ADDRESSING_MODE_STRINGS[] = { ADDRESSING_MODES }; #undef _ #define TEST_OPCODE(opcode) test_opcode = opcode; #define OPCODE_VARIANT(opcode, cycles, addressing_mode) \ if (opcode_from_ip == opcode) { \ *_opcode = test_opcode; \ *_addressing_mode = addressing_mode; \ *_cycles = cycles; \ } void fetch_next_opcode(uint8_t* _read_opcode, r_opcode* _opcode, r_addressing_mode* _addressing_mode, uint8_t* _cycles) { /* * The following data has been transcribed from * https://www.atarimax.com/jindroush.atari.org/aopc.html */ r_opcode test_opcode = NO_OPCODE; uint8_t opcode_from_ip = rip8(); *_read_opcode = opcode_from_ip; TEST_OPCODE(ADC) OPCODE_VARIANT(0x69, 2, immediate) OPCODE_VARIANT(0x65, 3, zero_page) OPCODE_VARIANT(0x75, 4, zero_page_x) OPCODE_VARIANT(0x6D, 4, absolute) OPCODE_VARIANT(0x7D, 4, absolute_x) OPCODE_VARIANT(0x79, 4, absolute_y) OPCODE_VARIANT(0x61, 6, indexed_indirect_x) OPCODE_VARIANT(0x71, 6, indirect_indexed_y) TEST_OPCODE(AND) OPCODE_VARIANT(0x29, 2, immediate) OPCODE_VARIANT(0x25, 2, zero_page) OPCODE_VARIANT(0x35, 3, zero_page_x) OPCODE_VARIANT(0x2D, 4, absolute) OPCODE_VARIANT(0x3D, 4, absolute_x) OPCODE_VARIANT(0x39, 4, absolute_y) OPCODE_VARIANT(0x21, 6, indexed_indirect_x) OPCODE_VARIANT(0x31, 5, indirect_indexed_y) TEST_OPCODE(ASL) OPCODE_VARIANT(0x0A, 2, accumulator) OPCODE_VARIANT(0x06, 5, zero_page) OPCODE_VARIANT(0x16, 6, zero_page_x) OPCODE_VARIANT(0x0E, 6, absolute) OPCODE_VARIANT(0x1E, 7, absolute_x) TEST_OPCODE(BIT) OPCODE_VARIANT(0x24, 3, zero_page) OPCODE_VARIANT(0x2C, 4, absolute) TEST_OPCODE(BPL) OPCODE_VARIANT(0x10, 2, relative) TEST_OPCODE(BRA) OPCODE_VARIANT(0x80, 2, relative) TEST_OPCODE(BMI) OPCODE_VARIANT(0x30, 2, relative) TEST_OPCODE(BVC) OPCODE_VARIANT(0x50, 2, relative) TEST_OPCODE(BVS) OPCODE_VARIANT(0x70, 2, relative) TEST_OPCODE(BCC) OPCODE_VARIANT(0x90, 2, relative) TEST_OPCODE(BCS) OPCODE_VARIANT(0xB0, 2, relative) TEST_OPCODE(BNE) OPCODE_VARIANT(0xD0, 2, relative) TEST_OPCODE(BEQ) OPCODE_VARIANT(0xF0, 2, relative) TEST_OPCODE(BRK) OPCODE_VARIANT(0x00, 7, implied) TEST_OPCODE(CMP) OPCODE_VARIANT(0xC9, 2, immediate) OPCODE_VARIANT(0xC5, 3, zero_page) OPCODE_VARIANT(0xD5, 4, zero_page_x) OPCODE_VARIANT(0xCD, 4, absolute) OPCODE_VARIANT(0xDD, 4, absolute_x) OPCODE_VARIANT(0xD9, 4, absolute_y) OPCODE_VARIANT(0xC1, 6, indexed_indirect_x) OPCODE_VARIANT(0xD1, 5, indirect_indexed_y) TEST_OPCODE(CPX) OPCODE_VARIANT(0xE0, 2, immediate) OPCODE_VARIANT(0xE4, 3, zero_page) OPCODE_VARIANT(0xEC, 4, absolute) TEST_OPCODE(CPY) OPCODE_VARIANT(0xC0, 2, immediate) OPCODE_VARIANT(0xC4, 3, zero_page) OPCODE_VARIANT(0xCC, 4, absolute) TEST_OPCODE(DEC) OPCODE_VARIANT(0xC6, 5, zero_page) OPCODE_VARIANT(0xD6, 6, zero_page_x) OPCODE_VARIANT(0xCE, 6, absolute) OPCODE_VARIANT(0xDE, 7, absolute_x) TEST_OPCODE(EOR) OPCODE_VARIANT(0x49, 2, immediate) OPCODE_VARIANT(0x45, 3, zero_page) OPCODE_VARIANT(0x55, 4, zero_page_x) OPCODE_VARIANT(0x4D, 4, absolute) OPCODE_VARIANT(0x5D, 4, absolute_x) OPCODE_VARIANT(0x59, 4, absolute_y) OPCODE_VARIANT(0x41, 6, indexed_indirect_x) OPCODE_VARIANT(0x51, 5, indirect_indexed_y) TEST_OPCODE(CLC) OPCODE_VARIANT(0x18, 2, implied) TEST_OPCODE(SEC) OPCODE_VARIANT(0x38, 2, implied) TEST_OPCODE(CLI) OPCODE_VARIANT(0x58, 2, implied) TEST_OPCODE(SEI) OPCODE_VARIANT(0x78, 2, implied) TEST_OPCODE(CLV) OPCODE_VARIANT(0xB8, 2, implied) TEST_OPCODE(CLD) OPCODE_VARIANT(0xD8, 2, implied) TEST_OPCODE(SED) OPCODE_VARIANT(0xF8, 2, implied) TEST_OPCODE(INC) OPCODE_VARIANT(0xE6, 5, zero_page) OPCODE_VARIANT(0xF6, 6, zero_page_x) OPCODE_VARIANT(0xEE, 6, absolute) OPCODE_VARIANT(0xFe, 7, absolute_x) TEST_OPCODE(JMP) OPCODE_VARIANT(0x4C, 3, absolute) OPCODE_VARIANT(0x6C, 5, indirect) TEST_OPCODE(JSR) OPCODE_VARIANT(0x20, 6, absolute) TEST_OPCODE(LDA) OPCODE_VARIANT(0xA9, 2, immediate) OPCODE_VARIANT(0xA5, 3, zero_page) OPCODE_VARIANT(0xB5, 4, zero_page_x) OPCODE_VARIANT(0xAD, 4, absolute) OPCODE_VARIANT(0xBD, 4, absolute_x) OPCODE_VARIANT(0xB9, 4, absolute_y) OPCODE_VARIANT(0xA1, 6, indexed_indirect_x) OPCODE_VARIANT(0xB1, 5, indirect_indexed_y) TEST_OPCODE(LDX) OPCODE_VARIANT(0xA2, 2, immediate) OPCODE_VARIANT(0xA6, 3, zero_page) OPCODE_VARIANT(0xB6, 4, zero_page_y) OPCODE_VARIANT(0xAE, 4, absolute) OPCODE_VARIANT(0xBE, 4, absolute_y) TEST_OPCODE(LDY) OPCODE_VARIANT(0xA0, 2, immediate) OPCODE_VARIANT(0xA4, 3, zero_page) OPCODE_VARIANT(0xB4, 4, zero_page_x) OPCODE_VARIANT(0xAC, 4, absolute) OPCODE_VARIANT(0xBC, 4, absolute_x) TEST_OPCODE(LSR) OPCODE_VARIANT(0x4A, 2, accumulator) OPCODE_VARIANT(0x46, 5, zero_page) OPCODE_VARIANT(0x56, 6, zero_page_x) OPCODE_VARIANT(0x4E, 6, absolute) OPCODE_VARIANT(0x5E, 7, absolute_x) TEST_OPCODE(NOP) OPCODE_VARIANT(0xEA, 2, implied) TEST_OPCODE(ORA) OPCODE_VARIANT(0x09, 2, immediate) OPCODE_VARIANT(0x05, 2, zero_page) OPCODE_VARIANT(0x15, 3, zero_page_x) OPCODE_VARIANT(0x0D, 4, absolute) OPCODE_VARIANT(0x1D, 4, absolute_x) OPCODE_VARIANT(0x19, 4, absolute_y) OPCODE_VARIANT(0x01, 6, indexed_indirect_x) OPCODE_VARIANT(0x11, 5, indirect_indexed_y) TEST_OPCODE(TAX) OPCODE_VARIANT(0xAA, 2, implied) TEST_OPCODE(TXA) OPCODE_VARIANT(0x8A, 2, implied) TEST_OPCODE(DEA) OPCODE_VARIANT(0x3A, 2, implied) TEST_OPCODE(INA) OPCODE_VARIANT(0x1A, 2, implied) TEST_OPCODE(DEX) OPCODE_VARIANT(0xCA, 2, implied) TEST_OPCODE(INX) OPCODE_VARIANT(0xE8, 2, implied) TEST_OPCODE(TAY) OPCODE_VARIANT(0xA8, 2, implied) TEST_OPCODE(TYA) OPCODE_VARIANT(0x98, 2, implied) TEST_OPCODE(DEY) OPCODE_VARIANT(0x88, 2, implied) TEST_OPCODE(INY) OPCODE_VARIANT(0xC8, 2, implied) TEST_OPCODE(ROL) OPCODE_VARIANT(0x2A, 2, accumulator) OPCODE_VARIANT(0x26, 5, zero_page) OPCODE_VARIANT(0x36, 6, zero_page_x) OPCODE_VARIANT(0x2E, 6, absolute) OPCODE_VARIANT(0x3E, 7, absolute_x) TEST_OPCODE(ROR) OPCODE_VARIANT(0x6A, 2, accumulator) OPCODE_VARIANT(0x66, 5, zero_page) OPCODE_VARIANT(0x76, 6, zero_page_x) OPCODE_VARIANT(0x6E, 6, absolute) OPCODE_VARIANT(0x7E, 7, absolute_x) TEST_OPCODE(RTI) OPCODE_VARIANT(0x40, 6, implied) TEST_OPCODE(RTS) OPCODE_VARIANT(0x60, 6, implied) TEST_OPCODE(SBC) OPCODE_VARIANT(0xE9, 2, immediate) OPCODE_VARIANT(0xE5, 3, zero_page) OPCODE_VARIANT(0xF5, 4, zero_page_x) OPCODE_VARIANT(0xED, 4, absolute) OPCODE_VARIANT(0xFD, 4, absolute_x) OPCODE_VARIANT(0xF9, 4, absolute_y) OPCODE_VARIANT(0xE1, 6, indexed_indirect_x) OPCODE_VARIANT(0xF1, 5, indirect_indexed_y) TEST_OPCODE(STA) OPCODE_VARIANT(0x85, 3, zero_page) OPCODE_VARIANT(0x95, 4, zero_page_x) OPCODE_VARIANT(0x8D, 4, absolute) OPCODE_VARIANT(0x9D, 5, absolute_x) /* no page cross penalty? */ OPCODE_VARIANT(0x99, 5, absolute_y) OPCODE_VARIANT(0x81, 6, indexed_indirect_x) OPCODE_VARIANT(0x91, 6, indirect_indexed_y) OPCODE_VARIANT(0x92, 5, zero_page_indirect) TEST_OPCODE(TXS) OPCODE_VARIANT(0x9A, 2, implied) TEST_OPCODE(TSX) OPCODE_VARIANT(0xBA, 2, implied) TEST_OPCODE(PHA) OPCODE_VARIANT(0x48, 3, implied) TEST_OPCODE(PLA) OPCODE_VARIANT(0x68, 4, implied) TEST_OPCODE(PLX) OPCODE_VARIANT(0xFA, 4, implied) TEST_OPCODE(PLY) OPCODE_VARIANT(0x7A, 4, implied) TEST_OPCODE(PHP) OPCODE_VARIANT(0x08, 3, implied) TEST_OPCODE(PHX) OPCODE_VARIANT(0xDA, 3, implied) TEST_OPCODE(PHY) OPCODE_VARIANT(0x5A, 3, implied) TEST_OPCODE(PLP) OPCODE_VARIANT(0x28, 4, implied) TEST_OPCODE(STX) OPCODE_VARIANT(0x86, 3, zero_page) OPCODE_VARIANT(0x96, 4, zero_page_y) OPCODE_VARIANT(0x8E, 4, absolute) TEST_OPCODE(STY) OPCODE_VARIANT(0x84, 3, zero_page) OPCODE_VARIANT(0x94, 4, zero_page_x) OPCODE_VARIANT(0x8C, 4, absolute) TEST_OPCODE(STZ) OPCODE_VARIANT(0x64, 3, zero_page) OPCODE_VARIANT(0x74, 4, zero_page_x) OPCODE_VARIANT(0x9C, 4, absolute) OPCODE_VARIANT(0x9E, 5, absolute_x) } void branch(uint8_t condition, int8_t offset, uint8_t* cycles) { if (condition) { // branch succeeds *cycles += 1; if ((cpu.ip & 0xfff0) != ((cpu.ip + offset) & 0xfff0)) *cycles += 1; cpu.ip += offset; } } void handle_next_opcode() { uint16_t old_ip = cpu.ip; // fetch opcode, addressing mode and cycles for next instruction uint8_t read_opcode = 0; r_opcode opcode = NO_OPCODE; r_addressing_mode addressing_mode = NO_ADDRESSING_MODE; uint8_t cycles = 0; fetch_next_opcode(&read_opcode, &opcode, &addressing_mode, &cycles); if (opcode == NO_OPCODE || addressing_mode == NO_ADDRESSING_MODE) { printf("Unhandled opcode at %04x: %02x\n", old_ip, read_opcode); exit(1); } // handle addressing modes, store result in target_address uint16_t target_address = 0; uint8_t immediate_value = 0; int8_t relative_offset = 0; switch (addressing_mode) { case immediate: immediate_value = rip8(); break; case relative: relative_offset = (int8_t)rip8(); break; case absolute: target_address = rip16(); break; case zero_page: target_address = rip8(); break; case indirect: target_address = read16(rip16()); break; case zero_page_indirect: target_address = read16(rip8()); break; case zero_page_x: target_address = (rip8() + cpu.x) % 0xff; break; case zero_page_y: target_address = (rip8() + cpu.y) % 0xff; break; case absolute_x: target_address = rip16(); if ((target_address >> 12) != ((target_address + cpu.x) >> 12)) cycles += 1; target_address += cpu.x; break; case absolute_y: target_address = rip16(); if ((target_address >> 12) != ((target_address + cpu.y) >> 12)) cycles += 1; target_address += cpu.y; break; case indexed_indirect_x: target_address = read16((rip8() + cpu.x) & 0xff); break; case indirect_indexed_y: target_address = cpu.y; uint16_t temp = read16(rip8()); if ((target_address >> 12) != ((target_address + temp) >> 12)) cycles += 1; target_address += temp; break; } if (show_log) { printf("%04x | %d | %02x | %s %-18s | ", old_ip, cycles, read_opcode, OPCODE_STRINGS[opcode], ADDRESSING_MODE_STRINGS[addressing_mode] ); } int unhandled_opcode = 0; uint8_t t8 = 0; uint16_t t16 = 0; // handle opcode switch (opcode) { case ADC: adc((addressing_mode == immediate) ? immediate_value : read8(target_address)); set_flag(OVERFLOW, test_flag(CARRY) ^ test_flag(NEGATIVE)); break; case AND: t8 = (addressing_mode == immediate) ? immediate_value : read8(target_address); cpu.a &= t8; update_zero_and_negative_flags(cpu.a); break; case ASL: if (addressing_mode == accumulator) { set_flag(CARRY, cpu.a & 0x80); cpu.a <<= 1; update_zero_and_negative_flags(cpu.a); } else { t8 = read8(target_address); set_flag(CARRY, t8 & 0x80); t8 <<= 1; update_zero_and_negative_flags(t8); write8(target_address, t8); } break; case BCC: branch(!test_flag(CARRY), relative_offset, &cycles); break; case BCS: branch(test_flag(CARRY), relative_offset, &cycles); break; case BEQ: branch(test_flag(ZERO), relative_offset, &cycles); break; case BIT: t8 = read8(target_address); uint8_t temp = cpu.a; temp &= t8; update_zero_and_negative_flags(temp); set_flag(NEGATIVE, t8 & 0x80); set_flag(OVERFLOW, t8 & 0x40); break; case BMI: branch(test_flag(NEGATIVE), relative_offset, &cycles); break; case BNE: branch(!test_flag(ZERO), relative_offset, &cycles); break; case BPL: branch(!test_flag(NEGATIVE), relative_offset, &cycles); break; case BRA: branch(1, relative_offset, &cycles); break; case BRK: unhandled_opcode = 1; break; case BVC: if (old_ip == 0xf5b0) // TODO: REMOVE THIS HACK branch(1, relative_offset, &cycles); else branch(!test_flag(OVERFLOW), relative_offset, &cycles); break; case BVS: branch(test_flag(OVERFLOW), relative_offset, &cycles); break; case CLC: set_flag(CARRY, 0); break; case CLD: set_flag(DECIMAL_MODE, 0); break; case CLI: // is this the right flag 0x04 ? set_flag(INTERRUPT_DISABLE, 0); break; case CLV: set_flag(OVERFLOW, 0); break; case CMP: t8 = (addressing_mode == immediate) ? immediate_value : read8(target_address); cmp(cpu.a, t8); break; case CPX: t8 = (addressing_mode == immediate) ? immediate_value : read8(target_address); cmp(cpu.x, t8); break; case CPY: t8 = (addressing_mode == immediate) ? immediate_value : read8(target_address); cmp(cpu.y, t8); break; case DEC: t8 = read8(target_address); t8 -= 1; write8(target_address, t8); update_zero_and_negative_flags(t8); break; case DEA: cpu.a -= 1; update_zero_and_negative_flags(cpu.a); break; case DEX: cpu.x -= 1; update_zero_and_negative_flags(cpu.x); break; case DEY: cpu.y -= 1; update_zero_and_negative_flags(cpu.y); break; case EOR: t8 = (addressing_mode == immediate) ? immediate_value : read8(target_address); cpu.a ^= t8; update_zero_and_negative_flags(cpu.a); break; case INC: t8 = read8(target_address); t8 += 1; write8(target_address, t8); update_zero_and_negative_flags(t8); break; case INA: cpu.a += 1; update_zero_and_negative_flags(cpu.a); break; case INX: cpu.x += 1; update_zero_and_negative_flags(cpu.x); break; case INY: cpu.y += 1; update_zero_and_negative_flags(cpu.y); break; case JMP: cpu.ip = target_address; // TODO handle page boundary behaviour? break; case JSR: // push IP - 1 because target address has already been read push(((cpu.ip - 1) >> 8) & 0xff); push((cpu.ip - 1) & 0xff); cpu.ip = target_address; break; case LDA: cpu.a = (addressing_mode == immediate) ? immediate_value : read8(target_address); update_zero_and_negative_flags(cpu.a); break; case LDX: cpu.x = (addressing_mode == immediate) ? immediate_value : read8(target_address); update_zero_and_negative_flags(cpu.x); break; case LDY: cpu.y = (addressing_mode == immediate) ? immediate_value : read8(target_address); update_zero_and_negative_flags(cpu.y); break; case LSR: if (addressing_mode == accumulator) { set_flag(CARRY, cpu.a & 1); cpu.a >>= 1; update_zero_and_negative_flags(cpu.a); } else { t8 = read8(target_address); set_flag(CARRY, t8 & 1); t8 >>= 1; update_zero_and_negative_flags(t8); write8(target_address, t8); } break; case NOP: break; case ORA: t8 = (addressing_mode == immediate) ? immediate_value : read8(target_address); cpu.a |= t8; update_zero_and_negative_flags(cpu.a); break; case PHA: push(cpu.a); break; case PHX: push(cpu.x); break; case PHY: push(cpu.y); break; case PHP: push(cpu.flags); break; case PLA: cpu.a = pop(); break; case PLX: cpu.x = pop(); break; case PLY: cpu.y = pop(); break; case PLP: pop(cpu.flags); break; case ROL: if (addressing_mode == accumulator) { cpu.a = rol(cpu.a); update_zero_and_negative_flags(cpu.a); } else { t8 = rol(read8(target_address)); write8(target_address, t8); update_zero_and_negative_flags(t8); } break; case ROR: if (addressing_mode == accumulator) { cpu.a = ror(cpu.a); update_zero_and_negative_flags(cpu.a); } else { t8 = ror(read8(target_address)); write8(target_address, t8); update_zero_and_negative_flags(t8); } break; case RTI: cpu.flags = pop(); t16 = pop(); t16 |= ((uint16_t)pop()) << 8; cpu.ip = t16; break; case RTS: t16 = pop(); t16 |= ((uint16_t)pop()) << 8; cpu.ip = t16 + 1; break; case SBC: sbc((addressing_mode == immediate) ? immediate_value : read8(target_address)); set_flag(OVERFLOW, test_flag(CARRY) ^ test_flag(NEGATIVE)); break; case SEC: set_flag(CARRY, 1); break; case SED: set_flag(DECIMAL_MODE, 1); break; case SEI: // is this the right flag 0x04 ? set_flag(INTERRUPT_DISABLE, 1); break; case STA: write8(target_address, cpu.a); break; case STX: write8(target_address, cpu.x); break; case STY: write8(target_address, cpu.y); break; case STZ: write8(target_address, 0); break; case TAX: cpu.x = cpu.a; update_zero_and_negative_flags(cpu.x); break; case TAY: cpu.y = cpu.a; update_zero_and_negative_flags(cpu.y); break; case TSX: cpu.x = cpu.sp; break; case TXA: cpu.a = cpu.x; update_zero_and_negative_flags(cpu.a); break; case TXS: cpu.sp = cpu.x; break; case TYA: cpu.a = cpu.y; update_zero_and_negative_flags(cpu.a); break; default: unhandled_opcode = 1; break; }; if (unhandled_opcode) { printf("Opcode not implemented yet!\n"); exit(1); } cpu.total_cycles += cycles; if (show_log) { printf("A: %02x, X: %02x, Y: %02x, FLAGS: %02x, PC: %04x, SP: %02x | %10ld", cpu.a, cpu.x, cpu.y, cpu.flags, cpu.ip, cpu.sp, cpu.total_cycles); printf("\n"); } } void set_pixel(int px, int py, unsigned int color) { int x, y; XSetForeground(dsp, gc, color); for (y = 0; y < SCALE; y++) for (x = 0; x < SCALE; x++) XDrawPoint(dsp, win, gc, px * SCALE + x, py * SCALE + y); } void render_hires_screen() { uint8_t current_screen = ram[0x30b]; int x, y; for (y = 0; y < 192; y++) { uint16_t line_offset = yoffset[y] | (current_screen == 1 ? 0x2000 : 0x4000); for (x = 0; x < 40; x++) { uint8_t byte = ram[line_offset + x]; for (int px = 0; px < 7; px++) set_pixel(x * 7 + px, y, ((byte >> px) & 1) ? white : black); } } } int main(int argc, char** argv) { if (argc < 2) { printf("Usage: ./champ [options] \n"); printf("\n"); printf("Options:\n"); printf(" --show-screen\n"); printf(" --hide-log\n"); exit(1); } for (int i = 1; i < argc; i++) { if (strcmp(argv[i], "--show-screen") == 0) show_screen = 1; if (strcmp(argv[i], "--hide-log") == 0) show_log = 0; } memset(ram, 0, 0x10000); load(argv[argc - 1], 0); if (show_screen) init_display(); init_cpu(&cpu); cpu.ip = 0x6000; struct timespec tstart = {0, 0}; clock_gettime(CLOCK_MONOTONIC, &tstart); unsigned long start_time = tstart.tv_sec * 1000000000 + tstart.tv_nsec; uint32_t next_display_refresh = 0; uint8_t old_screen_number = 0; while (1) { if (cpu.ip >= 0xf5b2) printf("*** "); handle_next_opcode(); // if (cycles) // { // // struct timespec tlap = {0, 0}; // // clock_gettime(CLOCK_MONOTONIC, &tlap); // // unsigned long lap_time = tlap.tv_sec * 1000000000 + tlap.tv_nsec; // // unsigned long elapsed_time = lap_time - start_time; // // start_time = lap_time; // // printf("Time taken for %d cycles: %ld\n", cycles, elapsed_time); // } // else // break; if (show_screen) { if (XEventsQueued(dsp, QueuedAfterFlush) > 0) { int exit_program = 0; XNextEvent(dsp, &evt); switch (evt.type) { case (KeyRelease) : if (evt.xkey.keycode == keyQ) exit_program = 1; case (ClientMessage) : if (evt.xclient.data.l[0] == wmDelete) exit_program = 1; break; } if (exit_program) break; } if (ram[0x30b] != old_screen_number) { old_screen_number = ram[0x30b]; render_hires_screen(); } } } printf("Total cycles: %d\n", cpu.total_cycles); return 0; }