8080-Emulator/emulator_shell.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h> // for the uintx_t's
#include <unistd.h> // for sleep
#include <string.h> // for memset

// gcc emulator_shell.c -o emulator

int disassemble8080(unsigned char* code) {
    int opbytes = 1;
    switch (*code) {
        case 0x00: printf("NOP"); break;

        case 0x01: printf("LXI B,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x02: printf("STAX B"); break;
        case 0x03: printf("INX B"); break;
        case 0x04: printf("INR B"); break;
        case 0x05: printf("DCR B"); break;
        case 0x06: printf("MVI B,#$%02x", code[1]); opbytes = 2; break;
        case 0x07: printf("RLC"); break;
        case 0x08: printf("NOP"); break;

        case 0x09: printf("DAD B"); break;
        case 0x0a: printf("LDAX B"); break; 
        case 0x0b: printf("DCX B"); break;
        case 0x0c: printf("INR C"); break;
        case 0x0d: printf("DCR C"); break;
        case 0x0e: printf("MVI C,#$%02x", code[1]); opbytes = 2; break;
        case 0x0f: printf("RRC"); break;
        case 0x10: printf("NOP"); break;

        case 0x11: printf("LXI D,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x12: printf("STAX D"); break;
        case 0x13: printf("INX D"); break;
        case 0x14: printf("INR D"); break;
        case 0x15: printf("DCR D"); break;
        case 0x16: printf("MVI D,#$%02x", code[1]); opbytes = 2; break;
        case 0x17: printf("RAL"); break;
        case 0x18: printf("NOP"); break;

        case 0x19: printf("DAD D"); break;
        case 0x1a: printf("LDAX D"); break;
        case 0x1b: printf("DCX D"); break;
        case 0x1c: printf("INR E"); break;
        case 0x1d: printf("DCR E"); break;
        case 0x1e: printf("MVI E,#$%02x", code[1]); opbytes = 2; break;
        case 0x1f: printf("RAR"); break;
        case 0x20: printf("NOP"); break;

        case 0x21: printf("LXI H,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x22: printf("SHLD $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x23: printf("INX H"); break;
        case 0x24: printf("INR H"); break;
        case 0x25: printf("DCR H"); break;
        case 0x26: printf("MVI H,#$%02x", code[1]); opbytes = 2; break;
        case 0x27: printf("DAA"); break;
        case 0x28: printf("NOP"); break;

        case 0x29: printf("DAD H"); break;
        case 0x2a: printf("LHLD $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x2b: printf("DCX H"); break;
        case 0x2c: printf("INR L"); break;
        case 0x2d: printf("DCR L"); break;
        case 0x2e: printf("MVI L,#$%02x", code[1]); opbytes = 2; break;
        case 0x2f: printf("CMA"); break;
        case 0x30: printf("NOP"); break;

        case 0x31: printf("LXI SP,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x32: printf("STA $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x33: printf("INX SP"); break;
        case 0x34: printf("INR M"); break;
        case 0x35: printf("DCR M"); break;
        case 0x36: printf("MVI M,#$%02x", code[1]); opbytes = 2; break;
        case 0x37: printf("STC"); break;
        case 0x38: printf("NOP"); break;

        case 0x39: printf("DAD SP"); break;
        case 0x3a: printf("LDA $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x3b: printf("DCX SP"); break;
        case 0x3c: printf("INR A"); break;
        case 0x3d: printf("DCR A"); break;
        case 0x3e: printf("MVI A,#$%02x", code[1]); opbytes = 2; break;
        case 0x3f: printf("CMC"); break;

        case 0x40: printf("MOV B,B"); break;
        case 0x41: printf("MOV B,C"); break;
        case 0x42: printf("MOV B,D"); break;
        case 0x43: printf("MOV B,E"); break;
        case 0x44: printf("MOV B,H"); break;
        case 0x45: printf("MOV B,L"); break;
        case 0x46: printf("MOV B,M"); break;
        case 0x47: printf("MOV B,A"); break;

        case 0x48: printf("MOV C,B"); break;
        case 0x49: printf("MOV C,C"); break;
        case 0x4a: printf("MOV C,D"); break;
        case 0x4b: printf("MOV C,E"); break;
        case 0x4c: printf("MOV C,H"); break;
        case 0x4d: printf("MOV C,L"); break;
        case 0x4e: printf("MOV C,M"); break;
        case 0x4f: printf("MOV C,A"); break;

        case 0x50: printf("MOV D,B"); break;
        case 0x51: printf("MOV D,C"); break;
        case 0x52: printf("MOV D,D"); break;
        case 0x53: printf("MOV D,E"); break;
        case 0x54: printf("MOV D,H"); break;
        case 0x55: printf("MOV D,L"); break;
        case 0x56: printf("MOV D,M"); break;
        case 0x57: printf("MOV D,A"); break;

        case 0x58: printf("MOV E,B"); break;
        case 0x59: printf("MOV E,C"); break;
        case 0x5a: printf("MOV E,D"); break;
        case 0x5b: printf("MOV E,E"); break;
        case 0x5c: printf("MOV E,H"); break;
        case 0x5d: printf("MOV E,L"); break;
        case 0x5e: printf("MOV E,M"); break;
        case 0x5f: printf("MOV E,A"); break;

        case 0x60: printf("MOV H,B"); break;
        case 0x61: printf("MOV H,C"); break;
        case 0x62: printf("MOV H,D"); break;
        case 0x63: printf("MOV H,E"); break;
        case 0x64: printf("MOV H,H"); break;
        case 0x65: printf("MOV H,L"); break;
        case 0x66: printf("MOV H,M"); break;
        case 0x67: printf("MOV H,A"); break;

        case 0x68: printf("MOV L,B"); break;
        case 0x69: printf("MOV L,C"); break;
        case 0x6a: printf("MOV L,D"); break;
        case 0x6b: printf("MOV L,E"); break;
        case 0x6c: printf("MOV L,H"); break;
        case 0x6d: printf("MOV L,L"); break;
        case 0x6e: printf("MOV L,M"); break;
        case 0x6f: printf("MOV L,A"); break;

        case 0x70: printf("MOV M,B"); break;
        case 0x71: printf("MOV M,C"); break;
        case 0x72: printf("MOV M,D"); break;
        case 0x73: printf("MOV M,E"); break;
        case 0x74: printf("MOV M,H"); break;
        case 0x75: printf("MOV M,L"); break;
        case 0x76: printf("HLT"); break;
        case 0x77: printf("MOV M,A"); break;

        case 0x78: printf("MOV A,B"); break;
        case 0x79: printf("MOV A,C"); break;
        case 0x7a: printf("MOV A,D"); break;
        case 0x7b: printf("MOV A,E"); break;
        case 0x7c: printf("MOV A,H"); break;
        case 0x7d: printf("MOV A,L"); break;
        case 0x7e: printf("MOV A,M"); break;
        case 0x7f: printf("MOV A,A"); break;

        case 0x80: printf("ADD B"); break;
        case 0x81: printf("ADD C"); break;
        case 0x82: printf("ADD D"); break;
        case 0x83: printf("ADD E"); break;
        case 0x84: printf("ADD H"); break;
        case 0x85: printf("ADD L"); break;
        case 0x86: printf("ADD M"); break;
        case 0x87: printf("ADD A"); break;

        case 0x88: printf("ADC B"); break;
        case 0x89: printf("ADC C"); break;
        case 0x8a: printf("ADC D"); break;
        case 0x8b: printf("ADC E"); break;
        case 0x8c: printf("ADC H"); break;
        case 0x8d: printf("ADC L"); break;
        case 0x8e: printf("ADC M"); break;
        case 0x8f: printf("ADC A"); break;

        case 0x90: printf("SUB B"); break;
        case 0x91: printf("SUB C"); break;
        case 0x92: printf("SUB D"); break;
        case 0x93: printf("SUB E"); break;
        case 0x94: printf("SUB H"); break;
        case 0x95: printf("SUB L"); break;
        case 0x96: printf("SUB M"); break;
        case 0x97: printf("SUB A"); break;

        case 0x98: printf("SBB B"); break;
        case 0x99: printf("SBB C"); break;
        case 0x9a: printf("SBB D"); break;
        case 0x9b: printf("SBB E"); break;
        case 0x9c: printf("SBB H"); break;
        case 0x9d: printf("SBB L"); break;
        case 0x9e: printf("SBB M"); break;
        case 0x9f: printf("SBB A"); break;

        case 0xa0: printf("ANA B"); break;
        case 0xa1: printf("ANA C"); break;
        case 0xa2: printf("ANA D"); break;
        case 0xa3: printf("ANA E"); break;
        case 0xa4: printf("ANA H"); break;
        case 0xa5: printf("ANA L"); break;
        case 0xa6: printf("ANA M"); break;
        case 0xa7: printf("ANA A"); break;

        case 0xa8: printf("XRA B"); break;
        case 0xa9: printf("XRA C"); break;
        case 0xaa: printf("XRA D"); break;
        case 0xab: printf("XRA E"); break;
        case 0xac: printf("XRA H"); break;
        case 0xad: printf("XRA L"); break;
        case 0xae: printf("XRA M"); break;
        case 0xaf: printf("XRA A"); break;

        case 0xb0: printf("ORA B"); break;
        case 0xb1: printf("ORA C"); break;
        case 0xb2: printf("ORA D"); break;
        case 0xb3: printf("ORA E"); break;
        case 0xb4: printf("ORA H"); break;
        case 0xb5: printf("ORA L"); break;
        case 0xb6: printf("ORA M"); break;
        case 0xb7: printf("ORA A"); break;

        case 0xb8: printf("CMP B"); break;
        case 0xb9: printf("CMP C"); break;
        case 0xba: printf("CMP D"); break;
        case 0xbb: printf("CMP E"); break;
        case 0xbc: printf("CMP H"); break;
        case 0xbd: printf("CMP L"); break;
        case 0xbe: printf("CMP M"); break;
        case 0xbf: printf("CMP A"); break;

        case 0xc0: printf("RNZ"); break;
        case 0xc1: printf("POP B"); break;
        case 0xc2: printf("JNZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xc3: printf("JMP $%02x%02x",code[2],code[1]); opbytes = 3; break; 
        case 0xc4: printf("CNZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xc5: printf("PUSH B"); break;
        case 0xc6: printf("ADI,#$%02x", code[1]); opbytes = 2; break;
        case 0xc7: printf("RST 0"); break;

        case 0xc8: printf("RZ"); break;
        case 0xc9: printf("RET"); break;
        case 0xca: printf("JZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xcb: printf("NOP"); break;
        case 0xcc: printf("CZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xcd: printf("CALL $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xce: printf("ACI,#$%02x", code[1]); opbytes = 2; break;
        case 0xcf: printf("RST 1"); break;

        case 0xd0: printf("RNC"); break;
        case 0xd1: printf("POP D"); break;
        case 0xd2: printf("JNC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xd3: printf("OUT #$%02x", code[1]); opbytes = 2; break;
        case 0xd4: printf("CNC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xd5: printf("PUSH D"); break;
        case 0xd6: printf("SUI,#$%02x", code[1]); opbytes = 2; break;
        case 0xd7: printf("RST 2"); break;

        case 0xd8: printf("RC"); break;
        case 0xd9: printf("NOP"); break;
        case 0xda: printf("JC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xdb: printf("IN #$%02x", code[1]); opbytes = 2; break;
        case 0xdc: printf("CC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xdd: printf("NOP"); break;
        case 0xde: printf("SBI,#$%02x", code[1]); opbytes = 2; break;
        case 0xdf: printf("RST 3"); break;

        case 0xe0: printf("RPO"); break;
        case 0xe1: printf("POP H"); break;
        case 0xe2: printf("JPO $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xe3: printf("XTHL"); break;
        case 0xe4: printf("CPO $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xe5: printf("PUSH H"); break;
        case 0xe6: printf("ANI,#$%02x", code[1]); opbytes = 2; break;
        case 0xe7: printf("RST 4"); break;

        case 0xe8: printf("RPE"); break;
        case 0xe9: printf("PCHL"); break;
        case 0xea: printf("JPE $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xeb: printf("XCHG"); break;
        case 0xec: printf("CPE $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xed: printf("NOP"); break;
        case 0xee: printf("XRI,#$%02x", code[1]); opbytes = 2; break;
        case 0xef: printf("RST 5"); break;

        case 0xf0: printf("RP"); break;
        case 0xf1: printf("POP PSW"); break;
        case 0xf2: printf("JP $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xf3: printf("DI"); break;
        case 0xf4: printf("CP $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xf5: printf("PUSH PSW"); break;
        case 0xf6: printf("ORI,#$%02x", code[1]); opbytes = 2; break;
        case 0xf7: printf("RST 6"); break;

        case 0xf8: printf("RM"); break;
        case 0xf9: printf("SPHL"); break;
        case 0xfa: printf("JM $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xfb: printf("EI"); break;
        case 0xfc: printf("CM $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xfd: printf("NOP"); break;
        case 0xfe: printf("CPI,#$%02x", code[1]); opbytes = 2; break;
        case 0xff: printf("RST 7"); break;

    }
    printf("\n");
    return opbytes;
}


// ================= EMULATOR CODE ======================


typedef struct ConditionCodes {
    //bitfields for condition codes
    //the number following the variables sets the number of bits    
    uint8_t    z:1;    
    uint8_t    s:1;    
    uint8_t    p:1;    
    uint8_t    cy:1;    
    uint8_t    ac:1;    
    uint8_t    pad:3;    
} ConditionCodes;


typedef struct State8080 {    
    uint8_t    a;    
    uint8_t    b;    
    uint8_t    c;    
    uint8_t    d;    
    uint8_t    e;    
    uint8_t    h;    
    uint8_t    l;    
    uint16_t    sp;    
    uint16_t    pc;    
    uint8_t     *memory;    
    ConditionCodes      cc;    
    uint8_t     int_enable;    
} State8080;

void unknownInstruction(State8080* state) {
    printf("Error: Unknown instruction");
    return exit(1);
}

int parity(int x, int size)
{
	int i;
	int p = 0;
	x = (x & ((1<<size)-1));
	for (i=0; i<size; i++)
	{
		if (x & 0x1) p++;
		x = x >> 1;
	}
	return (0 == (p & 0x1));
}

int emulate8080(State8080* state) {
    unsigned char *opcode = &(state->memory[state->pc]);

    printf("%04x ", state->pc);

    disassemble8080(opcode);
    state->pc++;

    switch(*opcode) {
        case 0x00: break;       // NOP does nothing
        case 0x01:              // LXI B, word
            state->c = opcode[1];
            state->b = opcode[2];
            state->pc += 2;
            break;
        case 0x05:              // DCR B
            {
            uint8_t res = state->b - 1;
            state->b = res;
            state->cc.z = (res == 0);
            state->cc.s = (0x80 == (res & 0x80));
            state->cc.p = parity(res, 8);
            }
            break;
        case 0x06:              // MVI B, byte
            state->b = opcode[1];
            state->pc += 1;
            break;
        case 0x09:              // DAD B
            {
            uint32_t h1 = (state->h << 8) | state->l;
            uint32_t bc = (state->b << 8) | state->c;
            uint32_t result = h1 + bc;
            state->h = (result & 0xff00) >> 8;
            state->l = result & 0xff;
            state->cc.cy = ((result & 0xffff0000) != 0);
            }
            break;
        
        case 0x0d:              // DCR C
            {
            uint8_t res = state->c - 1;
            state->c = res;
            state->cc.z = (res == 0);
            state->cc.s = ((res & 0x80) == 0x80);
            state->cc.p = parity(res, 8);
            }
            break;
        case 0x0e:              // MVI C, byte
            state->c = opcode[1];
            state->pc++;
            break;
        case 0x0f:              // RRC
            {
            uint8_t x = state->a;
            state->a = ((x & 1) << 7) | (x >> 1);
            state->cc.cy = (1 == (x & 1));
            }
            break;
        case 0x11:              // LXI D, word
            {
            state->d = opcode[2];
            state->e = opcode[1];
            state->pc += 2;
            }
            break;
        case 0x13:              // INX D
            {
            state->e++;
            if (state->e == 0) {
                state->d++;
            }}
            break;
        case 0x19:              // DAD D
            {
            uint32_t h1 = (state->h << 8) | state->l;
            uint32_t de = (state->d << 8) | state->e;
            uint32_t result = h1 + de;
            state->h = (result & 0xff00) >> 8;
            state->l = result & 0xff;
            state->cc.cy = ((result & 0xffff0000) != 0);
            }
            break;
        case 0x1a:              // LDAX D
            {
            uint16_t de = (state->d << 8) | state->e;
            state->a = state->memory[de];
            }
            break;

        case 0x21:              // LXI H, word
            {
            state->h = opcode[2];
            state->l = opcode[1];
            state->pc += 2;
            break;
            }
        case 0x23:              // INX H
            {
            state->l++;
            if (state->l == 0) {
                state->h++;
            }}
            break;
        case 0x26:              // MVI H, byte
            {
            state->h = opcode[1];
            state->pc++;
            }
            break;
        case 0x29:              // DAD H
            {
            uint32_t hl = (state->h << 8) | state->l;
            uint32_t result = hl + hl;
            state->h = (result & 0xff00) >> 8;
            state->l = result & 0xff;
            state->cc.cy = ((result & 0xffff0000) != 0);
            }
            break;
        case 0x31:              // LXI SP, word
            state->sp = ((opcode[2] << 8) | opcode[1]);
            state->pc += 2;
            break;
        case 0x32:              // STA adress
            {
            uint16_t adress = (opcode[2]<<8) | (opcode[1]);
            state->memory[adress] = state->a;
            state->pc += 2;
            }
            break;

        case 0x36:              // MVI M, byte
            {
            uint16_t adress = (state->h <<8) | (state->l);
            state->memory[adress] = opcode[1];
            state->pc++;
            }
            break;

        case 0x3a:              // LDA adress
            {
            uint16_t adress = (opcode[2]<<8) | (opcode[1]);
            state->a = state->memory[adress];
            state->pc += 2;
            }
            break;
        case 0x3e:              // MVI A, byte
            state->a = opcode[1];
            state->pc++;
            break;
        case 0x41:              // MOV B, C
            state->b = state->c; 
            break;
        case 0x42:              // MOV B, D
            state->b = state->d; 
            break;
        case 0x43:              // MOV B, E
            state->b = state->e; 
            break;
        case 0x56:              // MOV D, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->d = state->memory[adress];
            }
            break;
        case 0x5e:              // MOV E, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->e = state->memory[adress];
            }
            break;
        case 0x66:              // MOV H, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->h = state->memory[adress];
            }
            break;
        case 0x6f:              // MOV L, A
            state->l = state->a;
            break;
        case 0x77:              // MOV M, A
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->memory[adress] = state->a;
            }
            break;
        case 0x7a:              // MOV A, D
            state->a = state->d;
            break;
        case 0x7b:              // MOV A, E
            state->a = state->e;
            break;
        case 0x7c:              // MOV A, H
            state->a = state->h;
            break;
        case 0x7e:              // MOV A, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->a = state->memory[adress];
            }
            break;
        case 0x80:              // ADD B
            {
            uint16_t answer = (uint16_t) state->a + (uint16_t) state->b;
            state->cc.z = ((answer & 0xff) == 0);
            state->cc.s = ((answer & 0x80) != 0);
            state->cc.cy = (answer > 0xff);
            state->cc.p = parity(answer & 0xff, 8);
            state->a = answer & 0xff;
            }
            break;

        case 0x86:              // ADD M
            {
            uint16_t offset = (state->h<<8) | (state->l);
            uint16_t answer = (uint16_t) state->a + state->memory[offset];
            state->cc.z = ((answer & 0xff) == 0);
            state->cc.s = ((answer & 0x80) != 0);
            state->cc.cy = (answer > 0xff);
            state->cc.p = parity(answer & 0xff, 8);
            state->a = answer & 0xff;
            }
            break;
        case 0x1f:              // RAR
            {
            uint8_t x = state->a;
            state->a = (state->cc.cy << 7) | (x >> 1);
            state->cc.cy = (1 == (x & 1));
            }
            break;

        case 0xa7:              // ANA A
            state->a &= state->a;
            state->cc.z = (state->a == 0);
            state->cc.s = (0x80 == (state->a & 0x80));
            state->cc.p = parity(state->a, 8);
            state->cc.cy = 0;
            state->cc.ac = 0;
            break;
        case 0xaf:              // XRA A
            state->a ^= state->a;
            state->cc.z = (state->a == 0);
            state->cc.s = (0x80 == (state->a & 0x80));
            state->cc.p = parity(state->a, 8);
            state->cc.cy = 0;
            state->cc.ac = 0;
            break;
        case 0xc1:              // POP B
            state->c = state->memory[state->sp];
            state->b = state->memory[state->sp+1];
            state->sp += 2;
            break;

        case 0xc2:              // JNZ adress
            if (0 == state-> cc.z) {
                state->pc = (opcode[2] << 8) | opcode[1];
            } else {
                state->pc += 2;
            }
            break;
        
        case 0xc3:              // JMP adress
            state->pc = (opcode[2] << 8) | opcode[1];
            break;

        case 0xc5:              // PUSH B
            state->memory[state->sp-1] = state->b;
            state->memory[state->sp-2] = state->c;
            state->sp -= 2;
            break;
        case 0xc6:              // ADI byte
            {
            uint16_t answer = (uint16_t) state->a + (uint16_t) opcode[1];
            state->cc.z = ((state->a & 0xff) == 0);
            state->cc.s = ((state->a & 0x80) == 0x80);
            state->cc.cy = (state->a > 0xff);
            state->cc.p = parity(state->a & 0xff, 8);
            state->pc++;
            }
            break;
        case 0xc9:              // RET
            state->pc = (state->memory[state->sp+1] << 8) | state->memory[state->sp];
            state->sp += 2;
            break;
        case 0xcd:              // CALL adress
            {
            uint16_t ret = state -> pc+2;
            state->memory[state->sp-1] = (ret >> 8) & 0xff;
            state->memory[state->sp-2] = (ret & 0xff);
            state->sp -= 2;
            state->pc = (opcode[2] << 8) | opcode[1];
            }
            break;
        case 0xd1:              // POP D
            state->e = state->memory[state->sp];
            state->d = state->memory[state->sp+1];
            state->sp += 2;
            break;
        case 0xd3:              // OUT byte
            printf("%c", opcode[1]);
            state->pc++;
            break;
        case 0xd5:              // PUSH D
            state->memory[state->sp-1] = state->d;
            state->memory[state->sp-2] = state->e;
            state->sp -= 2;
            break;
        
        case 0xe1:              // POP H
            state->l = state->memory[state->sp];
            state->h = state->memory[state->sp+1];
            state->sp += 2;
            break;
        case 0xe5:              // PUSH H
            state->memory[state->sp-1] = state->h;
            state->memory[state->sp-2] = state->l;
            state->sp -= 2;
            break;

        case 0x2f:              // CMA (NOT)
            state->a = ~state->a;
            break; 
        case 0xe6:              // ANI byte
            {
            uint8_t x = state->a & opcode[1];
            state->cc.z = (x == 0);
            state->cc.s = (0x80 == (x & 0x80));
            state->cc.cy = 0;
            state->cc.p = parity(x, 8);
            state->pc++;
            }
            break;
        
        case 0xeb:              // XCHG
            {
            uint8_t tmp = state->h;
            state->h = state->d;
            state->d = tmp;
            tmp = state->l;
            state->l = state->e;
            state->e = tmp;
            }
            break;

        case 0xf1:              // POP PSW
            {
            state->a = state->memory[state->sp+1];
            uint8_t psw = state->memory[state->sp];
            state->cc.z = (0x01 == (psw & 0x01));
            state->cc.s = (0x02 == (psw & 0x02));
            state->cc.p = (0x04 == (psw & 0x04));
            state->cc.cy = (0x08 == (psw & 0x08));
            state->cc.ac = (0x10 == (psw & 0x10));
            state->sp += 2;
            }
            break;
        
        case 0xf5:              // PUSH PSW
            state->memory[state->sp-1] = state->a;
            state->memory[state->sp-2] = (state->cc.z | (state->cc.s << 1) | (state->cc.p << 2) | (state->cc.cy << 3) | (state->cc.ac << 4));
            state->sp -= 2;
            break;

        case 0xfb:              // EI
            state->int_enable = 1;  break;	
            break;

        case 0xfe:              // CPI byte
            {
            uint8_t x = state->a - opcode[1];
            state->cc.z = (x == 0);
            state->cc.s = (0x80 == (x & 0x80));
            state->cc.cy = (state->a < opcode[1]);
            state->cc.p = parity(x, 8);
            state->pc++;
            }
            break;

        default: unknownInstruction(state); break;
    }
    printf("\tC=%d,P=%d,S=%d,Z=%d\n", state->cc.cy, state->cc.p,    
        state->cc.s, state->cc.z);    
    printf("\tA $%02x B $%02x C $%02x D $%02x E $%02x H $%02x L $%02x SP %04x\n",    
        state->a, state->b, state->c, state->d,    
        state->e, state->h, state->l, state->sp); 
    
}

void read_Space_Invaders_ROM(State8080* state, const char* filename, int offset) {
    //Works exclusively with the memory system of Space Invaders
    FILE* file = fopen(filename, "rb");
    if (file == NULL) {
        printf("Issue opening the file.\n");
        exit(1);
    }
    //Get the file size and read it into a memory buffer    
    fseek(file, 0L, SEEK_END);    
    int fsize = ftell(file);    
    fseek(file, 0L, SEEK_SET);

    uint8_t *buffer = &state->memory[offset];    

    fread(buffer, fsize, 1, file);    
    fclose(file);    

}

int main (void)  {

    //Initializations

    State8080 *state = (State8080*) malloc(sizeof(State8080));
    memset(state, 0, sizeof(State8080));
    state->cc.z = 1;
    state->cc.s = 1;
    state->cc.p = 1;
    state->cc.cy = 0;
    state->cc.ac = 1;    
    state->pc = 0;
    state->memory = malloc(0x10000);

    read_Space_Invaders_ROM(state, "ROM/invaders.h", 0);
    read_Space_Invaders_ROM(state, "ROM/invaders.g", 0x800);
    read_Space_Invaders_ROM(state, "ROM/invaders.f", 0x1000);
    read_Space_Invaders_ROM(state, "ROM/invaders.e", 0x1800);

    int i = 0;

    while (1) {
        //Show the command in the code
        printf("%d\t\t:", i);
        emulate8080(state);
        i++;
        sleep(0.00001);
    }
    free(state->memory);
    free(state);
    return 0;

}