/// \file /// \brief 6502 assembler and disassembler #include "types.h" #include "utils/xstring.h" #include "debug.h" #include "asm.h" #include "x6502.h" #include #include #include ///assembles the string to an instruction located at addr, storing opcodes in output buffer int Assemble(unsigned char *output, int addr, char *str) { //unsigned char opcode[3] = { 0,0,0 }; output[0] = output[1] = output[2] = 0; char astr[128],ins[4]; int len = strlen(str); if ((!len) || (len > 127)) return 1; strcpy(astr,str); str_ucase(astr); sscanf(astr,"%3s",ins); //get instruction if (strlen(ins) != 3) return 1; strcpy(astr,strstr(astr,ins)+3); //heheh, this is probably a bad idea, but let's do it anyway! if ((astr[0] != ' ') && (astr[0] != 0)) return 1; //remove all whitespace str_strip(astr,STRIP_SP|STRIP_TAB|STRIP_CR|STRIP_LF); //repair syntax chr_replace(astr,'[','('); //brackets chr_replace(astr,']',')'); chr_replace(astr,'{','('); chr_replace(astr,'}',')'); chr_replace(astr,';',0); //comments str_replace(astr,"0X","$"); //miscellaneous //This does the following: // 1) Sets opcode[0] on success, else returns 1. // 2) Parses text in *astr to build the rest of the assembled // data in 'opcode', else returns 1 on error. if (!strlen(astr)) { //Implied instructions if (!strcmp(ins,"BRK")) output[0] = 0x00; else if (!strcmp(ins,"PHP")) output[0] = 0x08; else if (!strcmp(ins,"ASL")) output[0] = 0x0A; else if (!strcmp(ins,"CLC")) output[0] = 0x18; else if (!strcmp(ins,"PLP")) output[0] = 0x28; else if (!strcmp(ins,"ROL")) output[0] = 0x2A; else if (!strcmp(ins,"SEC")) output[0] = 0x38; else if (!strcmp(ins,"RTI")) output[0] = 0x40; else if (!strcmp(ins,"PHA")) output[0] = 0x48; else if (!strcmp(ins,"LSR")) output[0] = 0x4A; else if (!strcmp(ins,"CLI")) output[0] = 0x58; else if (!strcmp(ins,"RTS")) output[0] = 0x60; else if (!strcmp(ins,"PLA")) output[0] = 0x68; else if (!strcmp(ins,"ROR")) output[0] = 0x6A; else if (!strcmp(ins,"SEI")) output[0] = 0x78; else if (!strcmp(ins,"DEY")) output[0] = 0x88; else if (!strcmp(ins,"TXA")) output[0] = 0x8A; else if (!strcmp(ins,"TYA")) output[0] = 0x98; else if (!strcmp(ins,"TXS")) output[0] = 0x9A; else if (!strcmp(ins,"TAY")) output[0] = 0xA8; else if (!strcmp(ins,"TAX")) output[0] = 0xAA; else if (!strcmp(ins,"CLV")) output[0] = 0xB8; else if (!strcmp(ins,"TSX")) output[0] = 0xBA; else if (!strcmp(ins,"INY")) output[0] = 0xC8; else if (!strcmp(ins,"DEX")) output[0] = 0xCA; else if (!strcmp(ins,"CLD")) output[0] = 0xD8; else if (!strcmp(ins,"INX")) output[0] = 0xE8; else if (!strcmp(ins,"NOP")) output[0] = 0xEA; else if (!strcmp(ins,"SED")) output[0] = 0xF8; else return 1; } else { //Instructions with Operands if (!strcmp(ins,"ORA")) output[0] = 0x01; else if (!strcmp(ins,"ASL")) output[0] = 0x06; else if (!strcmp(ins,"BPL")) output[0] = 0x10; else if (!strcmp(ins,"JSR")) output[0] = 0x20; else if (!strcmp(ins,"AND")) output[0] = 0x21; else if (!strcmp(ins,"BIT")) output[0] = 0x24; else if (!strcmp(ins,"ROL")) output[0] = 0x26; else if (!strcmp(ins,"BMI")) output[0] = 0x30; else if (!strcmp(ins,"EOR")) output[0] = 0x41; else if (!strcmp(ins,"LSR")) output[0] = 0x46; else if (!strcmp(ins,"JMP")) output[0] = 0x4C; else if (!strcmp(ins,"BVC")) output[0] = 0x50; else if (!strcmp(ins,"ADC")) output[0] = 0x61; else if (!strcmp(ins,"ROR")) output[0] = 0x66; else if (!strcmp(ins,"BVS")) output[0] = 0x70; else if (!strcmp(ins,"STA")) output[0] = 0x81; else if (!strcmp(ins,"STY")) output[0] = 0x84; else if (!strcmp(ins,"STX")) output[0] = 0x86; else if (!strcmp(ins,"BCC")) output[0] = 0x90; else if (!strcmp(ins,"LDY")) output[0] = 0xA0; else if (!strcmp(ins,"LDA")) output[0] = 0xA1; else if (!strcmp(ins,"LDX")) output[0] = 0xA2; else if (!strcmp(ins,"BCS")) output[0] = 0xB0; else if (!strcmp(ins,"CPY")) output[0] = 0xC0; else if (!strcmp(ins,"CMP")) output[0] = 0xC1; else if (!strcmp(ins,"DEC")) output[0] = 0xC6; else if (!strcmp(ins,"BNE")) output[0] = 0xD0; else if (!strcmp(ins,"CPX")) output[0] = 0xE0; else if (!strcmp(ins,"SBC")) output[0] = 0xE1; else if (!strcmp(ins,"INC")) output[0] = 0xE6; else if (!strcmp(ins,"BEQ")) output[0] = 0xF0; else return 1; { //Parse Operands // It's not the sexiest thing ever, but it works well enough! //TODO: // Add branches. // Fix certain instructions. (Setting bits is not 100% perfect.) // Fix instruction/operand matching. (Instructions like "jmp ($94),Y" are no good!) // Optimizations? int tmpint; char tmpchr,tmpstr[20]; if (sscanf(astr,"#$%2X%c",&tmpint,&tmpchr) == 1) { //#Immediate switch (output[0]) { case 0x20: case 0x4C: //Jumps case 0x10: case 0x30: case 0x50: case 0x70: //Branches case 0x90: case 0xB0: case 0xD0: case 0xF0: case 0x06: case 0x24: case 0x26: case 0x46: //Other instructions incapable of #Immediate case 0x66: case 0x81: case 0x84: case 0x86: case 0xC6: case 0xE6: return 1; default: //cheap hack for certain instructions switch (output[0]) { case 0xA0: case 0xA2: case 0xC0: case 0xE0: break; default: output[0] |= 0x08; break; } output[1] = tmpint; break; } } else if (sscanf(astr,"$%4X%c",&tmpint,&tmpchr) == 1) { //Absolute, Zero Page, Branch, or Jump switch (output[0]) { case 0x20: case 0x4C: //Jumps output[1] = (tmpint & 0xFF); output[2] = (tmpint >> 8); break; case 0x10: case 0x30: case 0x50: case 0x70: //Branches case 0x90: case 0xB0: case 0xD0: case 0xF0: tmpint -= (addr+2); if ((tmpint < -128) || (tmpint > 127)) return 1; output[1] = (tmpint & 0xFF); break; //return 1; //FIX ME default: if (tmpint > 0xFF) { //Absolute output[0] |= 0x0C; output[1] = (tmpint & 0xFF); output[2] = (tmpint >> 8); } else { //Zero Page output[0] |= 0x04; output[1] = (tmpint & 0xFF); } break; } } else if (sscanf(astr,"$%4X%s",&tmpint,tmpstr) == 2) { //Absolute,X, Zero Page,X, Absolute,Y or Zero Page,Y if (!strcmp(tmpstr,",X")) { //Absolute,X or Zero Page,X switch (output[0]) { case 0x20: case 0x4C: //Jumps case 0x10: case 0x30: case 0x50: case 0x70: //Branches case 0x90: case 0xB0: case 0xD0: case 0xF0: case 0x24: case 0x86: case 0xA2: case 0xC0: //Other instructions incapable of Absolute,X or Zero Page,X case 0xE0: return 1; default: if (tmpint > 0xFF) { //Absolute if (output[0] == 0x84) return 1; //No STY Absolute,X! output[0] |= 0x1C; output[1] = (tmpint & 0xFF); output[2] = (tmpint >> 8); } else { //Zero Page output[0] |= 0x14; output[1] = (tmpint & 0xFF); } break; } } else if (!strcmp(tmpstr,",Y")) { //Absolute,Y or Zero Page,Y switch (output[0]) { case 0x20: case 0x4C: //Jumps case 0x10: case 0x30: case 0x50: case 0x70: //Branches case 0x90: case 0xB0: case 0xD0: case 0xF0: case 0x06: case 0x24: case 0x26: case 0x46: //Other instructions incapable of Absolute,Y or Zero Page,Y case 0x66: case 0x84: case 0x86: case 0xA0: case 0xC0: case 0xC6: case 0xE0: case 0xE6: return 1; case 0xA2: //cheap hack for LDX output[0] |= 0x04; default: if (tmpint > 0xFF) { //Absolute if (output[0] == 0x86) return 1; //No STX Absolute,Y! output[0] |= 0x18; output[1] = (tmpint & 0xFF); output[2] = (tmpint >> 8); } else { //Zero Page if ((output[0] != 0x86) && (output[0] != 0xA2)) return 1; //only STX and LDX Absolute,Y! output[0] |= 0x10; output[1] = (tmpint & 0xFF); } break; } } else return 1; } else if (sscanf(astr,"($%4X%s",&tmpint,tmpstr) == 2) { //Jump (Indirect), (Indirect,X) or (Indirect),Y switch (output[0]) { case 0x20: //Jumps case 0x10: case 0x30: case 0x50: case 0x70: //Branches case 0x90: case 0xB0: case 0xD0: case 0xF0: case 0x06: case 0x24: case 0x26: case 0x46: //Other instructions incapable of Jump (Indirect), (Indirect,X) or (Indirect),Y case 0x66: case 0x84: case 0x86: case 0xA0: case 0xA2: case 0xC0: case 0xC6: case 0xE0: case 0xE6: return 1; default: if ((!strcmp(tmpstr,")")) && (output[0] == 0x4C)) { //Jump (Indirect) output[0] = 0x6C; output[1] = (tmpint & 0xFF); output[2] = (tmpint >> 8); } else if ((!strcmp(tmpstr,",X)")) && (tmpint <= 0xFF) && (output[0] != 0x4C)) { //(Indirect,X) output[1] = (tmpint & 0xFF); } else if ((!strcmp(tmpstr,"),Y")) && (tmpint <= 0xFF) && (output[0] != 0x4C)) { //(Indirect),Y output[0] |= 0x10; output[1] = (tmpint & 0xFF); } else return 1; break; } } else return 1; } } return 0; } ///disassembles the opcodes in the buffer assuming the provided address. Uses GetMem() and 6502 current registers to query referenced values. returns a static string buffer. char *Disassemble(int addr, uint8 *opcode) { static char str[64]={0},chr[5]={0}; uint16 tmp,tmp2; //these may be replaced later with passed-in values to make a lighter-weight disassembly mode that may not query the referenced values #define RX (X.X) #define RY (X.Y) switch (opcode[0]) { #define relative(a) { \ if (((a)=opcode[1])&0x80) (a) = addr-(((a)-1)^0xFF); \ else (a)+=addr; \ } #define absolute(a) { \ (a) = opcode[1] | opcode[2]<<8; \ } #define zpIndex(a,i) { \ (a) = (opcode[1]+(i))&0xFF; \ } #define indirectX(a) { \ (a) = (opcode[1]+RX)&0xFF; \ (a) = GetMem((a)) | (GetMem(((a)+1)&0xff))<<8; \ } #define indirectY(a) { \ (a) = GetMem(opcode[1]) | (GetMem((opcode[1]+1)&0xff))<<8; \ (a) += RY; \ } #ifdef BRK_3BYTE_HACK case 0x00: sprintf(str,"BRK %02X %02X", opcode[1], opcode[2]); break; #else case 0x00: strcpy(str,"BRK"); break; #endif //odd, 1-byte opcodes case 0x08: strcpy(str,"PHP"); break; case 0x0A: strcpy(str,"ASL"); break; case 0x18: strcpy(str,"CLC"); break; case 0x28: strcpy(str,"PLP"); break; case 0x2A: strcpy(str,"ROL"); break; case 0x38: strcpy(str,"SEC"); break; case 0x40: strcpy(str,"RTI"); break; case 0x48: strcpy(str,"PHA"); break; case 0x4A: strcpy(str,"LSR"); break; case 0x58: strcpy(str,"CLI"); break; case 0x60: strcpy(str,"RTS"); break; case 0x68: strcpy(str,"PLA"); break; case 0x6A: strcpy(str,"ROR"); break; case 0x78: strcpy(str,"SEI"); break; case 0x88: strcpy(str,"DEY"); break; case 0x8A: strcpy(str,"TXA"); break; case 0x98: strcpy(str,"TYA"); break; case 0x9A: strcpy(str,"TXS"); break; case 0xA8: strcpy(str,"TAY"); break; case 0xAA: strcpy(str,"TAX"); break; case 0xB8: strcpy(str,"CLV"); break; case 0xBA: strcpy(str,"TSX"); break; case 0xC8: strcpy(str,"INY"); break; case 0xCA: strcpy(str,"DEX"); break; case 0xD8: strcpy(str,"CLD"); break; case 0xE8: strcpy(str,"INX"); break; case 0xEA: strcpy(str,"NOP"); break; case 0xF8: strcpy(str,"SED"); break; //(Indirect,X) case 0x01: strcpy(chr,"ORA"); goto _indirectx; case 0x21: strcpy(chr,"AND"); goto _indirectx; case 0x41: strcpy(chr,"EOR"); goto _indirectx; case 0x61: strcpy(chr,"ADC"); goto _indirectx; case 0x81: strcpy(chr,"STA"); goto _indirectx; case 0xA1: strcpy(chr,"LDA"); goto _indirectx; case 0xC1: strcpy(chr,"CMP"); goto _indirectx; case 0xE1: strcpy(chr,"SBC"); goto _indirectx; _indirectx: indirectX(tmp); sprintf(str,"%s ($%02X,X) @ $%04X = #$%02X", chr,opcode[1],tmp,GetMem(tmp)); break; //Zero Page case 0x05: strcpy(chr,"ORA"); goto _zeropage; case 0x06: strcpy(chr,"ASL"); goto _zeropage; case 0x24: strcpy(chr,"BIT"); goto _zeropage; case 0x25: strcpy(chr,"AND"); goto _zeropage; case 0x26: strcpy(chr,"ROL"); goto _zeropage; case 0x45: strcpy(chr,"EOR"); goto _zeropage; case 0x46: strcpy(chr,"LSR"); goto _zeropage; case 0x65: strcpy(chr,"ADC"); goto _zeropage; case 0x66: strcpy(chr,"ROR"); goto _zeropage; case 0x84: strcpy(chr,"STY"); goto _zeropage; case 0x85: strcpy(chr,"STA"); goto _zeropage; case 0x86: strcpy(chr,"STX"); goto _zeropage; case 0xA4: strcpy(chr,"LDY"); goto _zeropage; case 0xA5: strcpy(chr,"LDA"); goto _zeropage; case 0xA6: strcpy(chr,"LDX"); goto _zeropage; case 0xC4: strcpy(chr,"CPY"); goto _zeropage; case 0xC5: strcpy(chr,"CMP"); goto _zeropage; case 0xC6: strcpy(chr,"DEC"); goto _zeropage; case 0xE4: strcpy(chr,"CPX"); goto _zeropage; case 0xE5: strcpy(chr,"SBC"); goto _zeropage; case 0xE6: strcpy(chr,"INC"); goto _zeropage; _zeropage: // ################################## Start of SP CODE ########################### // Change width to %04X // don't! sprintf(str,"%s $%02X = #$%02X", chr,opcode[1],GetMem(opcode[1])); // ################################## End of SP CODE ########################### break; //#Immediate case 0x09: strcpy(chr,"ORA"); goto _immediate; case 0x29: strcpy(chr,"AND"); goto _immediate; case 0x49: strcpy(chr,"EOR"); goto _immediate; case 0x69: strcpy(chr,"ADC"); goto _immediate; //case 0x89: strcpy(chr,"STA"); goto _immediate; //baka, no STA #imm!! case 0xA0: strcpy(chr,"LDY"); goto _immediate; case 0xA2: strcpy(chr,"LDX"); goto _immediate; case 0xA9: strcpy(chr,"LDA"); goto _immediate; case 0xC0: strcpy(chr,"CPY"); goto _immediate; case 0xC9: strcpy(chr,"CMP"); goto _immediate; case 0xE0: strcpy(chr,"CPX"); goto _immediate; case 0xE9: strcpy(chr,"SBC"); goto _immediate; _immediate: sprintf(str,"%s #$%02X", chr,opcode[1]); break; //Absolute case 0x0D: strcpy(chr,"ORA"); goto _absolute; case 0x0E: strcpy(chr,"ASL"); goto _absolute; case 0x2C: strcpy(chr,"BIT"); goto _absolute; case 0x2D: strcpy(chr,"AND"); goto _absolute; case 0x2E: strcpy(chr,"ROL"); goto _absolute; case 0x4D: strcpy(chr,"EOR"); goto _absolute; case 0x4E: strcpy(chr,"LSR"); goto _absolute; case 0x6D: strcpy(chr,"ADC"); goto _absolute; case 0x6E: strcpy(chr,"ROR"); goto _absolute; case 0x8C: strcpy(chr,"STY"); goto _absolute; case 0x8D: strcpy(chr,"STA"); goto _absolute; case 0x8E: strcpy(chr,"STX"); goto _absolute; case 0xAC: strcpy(chr,"LDY"); goto _absolute; case 0xAD: strcpy(chr,"LDA"); goto _absolute; case 0xAE: strcpy(chr,"LDX"); goto _absolute; case 0xCC: strcpy(chr,"CPY"); goto _absolute; case 0xCD: strcpy(chr,"CMP"); goto _absolute; case 0xCE: strcpy(chr,"DEC"); goto _absolute; case 0xEC: strcpy(chr,"CPX"); goto _absolute; case 0xED: strcpy(chr,"SBC"); goto _absolute; case 0xEE: strcpy(chr,"INC"); goto _absolute; _absolute: absolute(tmp); sprintf(str,"%s $%04X = #$%02X", chr,tmp,GetMem(tmp)); break; //branches case 0x10: strcpy(chr,"BPL"); goto _branch; case 0x30: strcpy(chr,"BMI"); goto _branch; case 0x50: strcpy(chr,"BVC"); goto _branch; case 0x70: strcpy(chr,"BVS"); goto _branch; case 0x90: strcpy(chr,"BCC"); goto _branch; case 0xB0: strcpy(chr,"BCS"); goto _branch; case 0xD0: strcpy(chr,"BNE"); goto _branch; case 0xF0: strcpy(chr,"BEQ"); goto _branch; _branch: relative(tmp); sprintf(str,"%s $%04X", chr,tmp); break; //(Indirect),Y case 0x11: strcpy(chr,"ORA"); goto _indirecty; case 0x31: strcpy(chr,"AND"); goto _indirecty; case 0x51: strcpy(chr,"EOR"); goto _indirecty; case 0x71: strcpy(chr,"ADC"); goto _indirecty; case 0x91: strcpy(chr,"STA"); goto _indirecty; case 0xB1: strcpy(chr,"LDA"); goto _indirecty; case 0xD1: strcpy(chr,"CMP"); goto _indirecty; case 0xF1: strcpy(chr,"SBC"); goto _indirecty; _indirecty: indirectY(tmp); sprintf(str,"%s ($%02X),Y @ $%04X = #$%02X", chr,opcode[1],tmp,GetMem(tmp)); break; //Zero Page,X case 0x15: strcpy(chr,"ORA"); goto _zeropagex; case 0x16: strcpy(chr,"ASL"); goto _zeropagex; case 0x35: strcpy(chr,"AND"); goto _zeropagex; case 0x36: strcpy(chr,"ROL"); goto _zeropagex; case 0x55: strcpy(chr,"EOR"); goto _zeropagex; case 0x56: strcpy(chr,"LSR"); goto _zeropagex; case 0x75: strcpy(chr,"ADC"); goto _zeropagex; case 0x76: strcpy(chr,"ROR"); goto _zeropagex; case 0x94: strcpy(chr,"STY"); goto _zeropagex; case 0x95: strcpy(chr,"STA"); goto _zeropagex; case 0xB4: strcpy(chr,"LDY"); goto _zeropagex; case 0xB5: strcpy(chr,"LDA"); goto _zeropagex; case 0xD5: strcpy(chr,"CMP"); goto _zeropagex; case 0xD6: strcpy(chr,"DEC"); goto _zeropagex; case 0xF5: strcpy(chr,"SBC"); goto _zeropagex; case 0xF6: strcpy(chr,"INC"); goto _zeropagex; _zeropagex: zpIndex(tmp,RX); // ################################## Start of SP CODE ########################### // Change width to %04X // don't! sprintf(str,"%s $%02X,X @ $%04X = #$%02X", chr,opcode[1],tmp,GetMem(tmp)); // ################################## End of SP CODE ########################### break; //Absolute,Y case 0x19: strcpy(chr,"ORA"); goto _absolutey; case 0x39: strcpy(chr,"AND"); goto _absolutey; case 0x59: strcpy(chr,"EOR"); goto _absolutey; case 0x79: strcpy(chr,"ADC"); goto _absolutey; case 0x99: strcpy(chr,"STA"); goto _absolutey; case 0xB9: strcpy(chr,"LDA"); goto _absolutey; case 0xBE: strcpy(chr,"LDX"); goto _absolutey; case 0xD9: strcpy(chr,"CMP"); goto _absolutey; case 0xF9: strcpy(chr,"SBC"); goto _absolutey; _absolutey: absolute(tmp); tmp2=(tmp+RY); sprintf(str,"%s $%04X,Y @ $%04X = #$%02X", chr,tmp,tmp2,GetMem(tmp2)); break; //Absolute,X case 0x1D: strcpy(chr,"ORA"); goto _absolutex; case 0x1E: strcpy(chr,"ASL"); goto _absolutex; case 0x3D: strcpy(chr,"AND"); goto _absolutex; case 0x3E: strcpy(chr,"ROL"); goto _absolutex; case 0x5D: strcpy(chr,"EOR"); goto _absolutex; case 0x5E: strcpy(chr,"LSR"); goto _absolutex; case 0x7D: strcpy(chr,"ADC"); goto _absolutex; case 0x7E: strcpy(chr,"ROR"); goto _absolutex; case 0x9D: strcpy(chr,"STA"); goto _absolutex; case 0xBC: strcpy(chr,"LDY"); goto _absolutex; case 0xBD: strcpy(chr,"LDA"); goto _absolutex; case 0xDD: strcpy(chr,"CMP"); goto _absolutex; case 0xDE: strcpy(chr,"DEC"); goto _absolutex; case 0xFD: strcpy(chr,"SBC"); goto _absolutex; case 0xFE: strcpy(chr,"INC"); goto _absolutex; _absolutex: absolute(tmp); tmp2=(tmp+RX); sprintf(str,"%s $%04X,X @ $%04X = #$%02X", chr,tmp,tmp2,GetMem(tmp2)); break; //jumps case 0x20: strcpy(chr,"JSR"); goto _jump; case 0x4C: strcpy(chr,"JMP"); goto _jump; case 0x6C: absolute(tmp); sprintf(str,"JMP ($%04X) = $%04X", tmp,GetMem(tmp)|GetMem(tmp+1)<<8); break; _jump: absolute(tmp); sprintf(str,"%s $%04X", chr,tmp); break; //Zero Page,Y case 0x96: strcpy(chr,"STX"); goto _zeropagey; case 0xB6: strcpy(chr,"LDX"); goto _zeropagey; _zeropagey: zpIndex(tmp,RY); // ################################## Start of SP CODE ########################### // Change width to %04X // don't! sprintf(str,"%s $%02X,Y @ $%04X = #$%02X", chr,opcode[1],tmp,GetMem(tmp)); // ################################## End of SP CODE ########################### break; //UNDEFINED default: strcpy(str,"ERROR"); break; } return str; }