6502の逆アセンブラを制作する（その２）

 6502の逆アセンブラを制作する過程の紹介の続きです

W65C816ボード

制作過程（５）--- pass1

いよいよここからが逆アセンブラの本体作成となりますが、まず検討すべきは命令の分類です。RockwellのデータシートによるとR65C02の命令は次の16通りに分類できるようです。

 0:(no opcode)

 1:Absolute 1:a

 2:Absolute Indexed Indirect 2:(a,x)

 3:Absolute Indexed with X 3:a,x

 4:Absolute Indexed with Y 4:a,y

 5:Absolute Indirect 5:(a)

 6:Accumulator 6:A

 7:Immediate 7:#

 8:Implied 8:i

 9:Program Counter Relative  9:r

10:Zero page Relative 10:zp,r

11:Zero page 11:zp

12:Zero page Indexed Indirect 12:(zp,x)

13:Zero page Indexed with X 13:zp,x

14:Zero page Indexed with Y 14:zp,y

15:Zero Page Indirect 15:(zp)

16:Zero Page Indirect Indexed with Y 16:(zp),y

これを元にして、オペコード、ニーモニック、命令長、命令タイプの表を作成しました。

それが下に示すファイルR65C02dopcode.hです。

         /****************************************************/ /* R65C02 dopcode.h */ /* */ /****************************************************/ /* optype 0:(no opcode) 1:Absolute 1:a 2:Absolute Indexed Indirect 2:(a,x) 3:Absolute Indexed with X 3:a,x 4:Absolute Indexed with Y 4:a,y 5:Absolute Indirect 5:(a) 6:Accumulator 6:A 7:Immediate 7:# 8:Implied 8:i 9:Program Counter Relative 9:r 10:Zero page Relative 10:zp,r 11:Zero page 11:zp 12:Zero page Indexed Indirect 12:(zp,x) 13:Zero page Indexed with X 13:zp,x 14:Zero page Indexed with Y 14:zp,y 15:Zero Page Indirect 15:(zp) 16:Zero Page Indirect Indexed with Y　16:(zp),y */ struct _MNE_TABLE { unsigned char opcode; char mnemonic[5]; unsigned int oplen; unsigned int optype; }; struct _MNE_TABLE OpcodeTbl[] = { /* opcode, mnemonic, oplen, optype */ {0x00,"BRK", 1, 8}, {0x01,"ORA", 2,12}, {0x02,"", 0, 0}, {0x03,"", 0, 0}, {0x04,"TSB", 2,11}, {0x05,"ORA", 2,11}, {0x06,"ASL", 2,11}, {0x07,"RMB0",2,11}, {0x08,"PHP", 1, 8}, {0x09,"ORA", 2, 7}, {0x0A,"ASL", 1, 6}, {0x0B,"", 0, 0}, {0x0C,"TSB", 3, 1}, {0x0D,"ORA", 3, 1}, {0x0E,"ASL", 3, 1}, {0x0F,"BBR0",3,10}, {0x10,"BPL", 2, 9}, {0x11,"ORA", 2,16}, {0x12,"ORA", 2,15}, {0x13,"", 0, 0}, {0x14,"TRB", 2,11}, {0x15,"ORA", 2,13}, {0x16,"ASL", 2,13}, {0x17,"RMB1",2,11}, {0x18,"CLC", 1, 8}, {0x19,"ORA", 3, 4}, {0x1A,"INC", 1, 6}, {0x1B,"", 0, 0}, {0x1C,"TRB", 3, 1}, {0x1D,"ORA", 3, 3}, {0x1E,"ASL", 3, 3}, {0x1F,"BBR1",3,10}, {0x20,"JSR", 3, 1}, {0x21,"AND", 2,12}, {0x22,"", 0, 0}, {0x23,"", 0, 0}, {0x24,"BIT", 2,11}, {0x25,"AND", 2,11}, {0x26,"ROL", 2,11}, {0x27,"RMB2",2,11}, {0x28,"PLP", 1, 8}, {0x29,"AND", 2, 7}, {0x2A,"ROL", 1, 6}, {0x2B,"", 0, 0}, {0x2C,"BIT", 3, 1}, {0x2D,"AND", 3, 1}, {0x2E,"ROL", 3, 1}, {0x2F,"BBR2",3,10}, {0x30,"BMI", 2, 9}, {0x31,"AND", 2,16}, {0x32,"AND", 2,15}, {0x33,"", 0, 0}, {0x34,"BIT", 2,13}, {0x35,"AND", 2,13}, {0x36,"ROL", 2,13}, {0x37,"RMB3",2,11}, {0x38,"SEC", 1, 8}, {0x39,"AND", 3, 4}, {0x3A,"DEC", 1, 6}, {0x3B,"", 0, 0}, {0x3C,"BIT", 3, 3}, {0x3D,"AND", 3, 3}, {0x3E,"ROL", 3, 3}, {0x3F,"BBR3",3,10}, {0x40,"RTI", 1, 8}, {0x41,"EOR", 2,12}, {0x42,"", 0, 0}, {0x43,"", 0, 0}, {0x44,"", 0, 0}, {0x45,"EOR", 2,11}, {0x46,"LSR", 2,11}, {0x47,"RMB4",2,11}, {0x48,"PHA", 1, 8}, {0x49,"EOR", 2, 7}, {0x4A,"LSR", 1, 6}, {0x4B,"", 0, 0}, {0x4C,"JMP", 3, 1}, {0x4D,"EOR", 3, 1}, {0x4E,"LSR", 3, 1}, {0x4F,"BBR4",3,10}, {0x50,"BVC", 2, 9}, {0x51,"EOR", 2,16}, {0x52,"EOR", 2,15}, {0x53,"", 0, 0}, {0x54,"", 0, 0}, {0x55,"EOR", 2,13}, {0x56,"LSR", 2,13}, {0x57,"RMB5",2,11}, {0x58,"CLI", 1, 8}, {0x59,"EOR", 3, 4}, {0x5A,"PHY", 1, 8}, {0x5B,"", 0, 0}, {0x5C,"", 0, 0}, {0x5D,"EOR", 3, 3}, {0x5E,"LSR", 3, 3}, {0x5F,"BBR5",3,10}, {0x60,"RTS", 1, 8}, {0x61,"ADC", 2,12}, {0x62,"", 0, 0}, {0x63,"", 0, 0}, {0x64,"STZ", 2,11}, {0x65,"ADC", 2,11}, {0x66,"ROR", 2,11}, {0x67,"RMB6",2,11}, {0x68,"PLA", 1, 8}, {0x69,"ADC", 2, 7}, {0x6A,"ROR", 1, 6}, {0x6B,"", 0, 0}, {0x6C,"JMP", 3, 5}, {0x6D,"ADC", 3, 1}, {0x6E,"ROR", 3, 1}, {0x6F,"BBR6",3,10}, {0x70,"BVS", 2, 9}, {0x71,"ADC", 2,16}, {0x72,"ADC", 2,15}, {0x73,"", 0, 0}, {0x74,"STZ", 2,13}, {0x75,"ADC", 2,13}, {0x76,"ROR", 2,13}, {0x77,"RMB7",2,11}, {0x78,"SEI", 1, 8}, {0x79,"ADC", 3, 4}, {0x7A,"PLY", 1, 8}, {0x7B,"", 0, 0}, {0x7C,"JMP", 3, 2}, {0x7D,"ADC", 3, 3}, {0x7E,"ROR", 3, 3}, {0x7F,"BBR7",3,10}, {0x80,"BRA", 2, 9}, {0x81,"STA", 2,12}, {0x82,"", 0, 0}, {0x83,"", 0, 0}, {0x84,"STY", 2,11}, {0x85,"STA", 2,11}, {0x86,"STX", 2,11}, {0x87,"SMB0",2,11}, {0x88,"DEY", 1, 8}, {0x89,"BIT", 2, 7}, {0x8A,"TXA", 1, 8}, {0x8B,"", 0, 0}, {0x8C,"STY", 3, 1}, {0x8D,"STA", 3, 1}, {0x8E,"STX", 3, 1}, {0x8F,"BBS0",3,10}, {0x90,"BCC", 2, 9}, {0x91,"STA", 2,16}, {0x92,"STA", 2,15}, {0x93,"", 0, 0}, {0x94,"STY", 2,13}, {0x95,"STA", 2,13}, {0x96,"STX", 2,14}, {0x97,"SMB1",2,11}, {0x98,"TYA", 1, 8}, {0x99,"STA", 3, 4}, {0x9A,"TXS", 1, 8}, {0x9B,"", 0, 0}, {0x9C,"STZ", 3, 1}, {0x9D,"STA", 3, 3}, {0x9E,"STZ", 3, 3}, {0x9F,"BBS1",3,10}, {0xA0,"LDY", 2, 7}, {0xA1,"LDA", 2,12}, {0xA2,"LDX", 2, 7}, {0xA3,"", 0, 0}, {0xA4,"LDY", 2,11}, {0xA5,"LDA", 2,11}, {0xA6,"LDX", 2,11}, {0xA7,"SMB2",2,11}, {0xA8,"TAY", 1, 8}, {0xA9,"LDA", 2, 7}, {0xAA,"TAX", 1, 8}, {0xAB,"", 0, 0}, {0xAC,"LDY", 3, 1}, {0xAD,"LDA", 3, 1}, {0xAE,"LDX", 3, 1}, {0xAF,"BBS2",3,10}, {0xB0,"BCS", 2, 9}, {0xB1,"LDA", 2,16}, {0xB2,"LDA", 2,15}, {0xB3,"", 0, 0}, {0xB4,"LDY", 2,13}, {0xB5,"LDA", 2,13}, {0xB6,"LDX", 2,14}, {0xB7,"SMB3",2,11}, {0xB8,"CLV", 1, 8}, {0xB9,"LDA", 3, 4}, {0xBA,"TSX", 1, 8}, {0xBB,"", 0, 0}, {0xBC,"LDY", 3, 3}, {0xBD,"LDA", 3, 3}, {0xBE,"LDX", 3, 4}, {0xBF,"BBS3",3,10}, {0xC0,"CPY", 2, 7}, {0xC1,"CMP", 2,12}, {0xC2,"", 0, 0}, {0xC3,"", 0, 0}, {0xC4,"CPY", 2,11}, {0xC5,"CMP", 2,11}, {0xC6,"DEC", 2,11}, {0xC7,"SMB4",2,11}, {0xC8,"INY", 1, 8}, {0xC9,"CMP", 2, 7}, {0xCA,"DEX", 1, 8}, {0xCB,"", 0, 0}, {0xCC,"CPY", 3, 1}, {0xCD,"CMP", 3, 1}, {0xCE,"DEC", 3, 1}, {0xCF,"BBS4",3,10}, {0xD0,"BNE", 2, 9}, {0xD1,"CMP", 2,16}, {0xD2,"CMP", 2,15}, {0xD3,"", 0, 0}, {0xD4,"", 0, 0}, {0xD5,"CMP", 2,13}, {0xD6,"DEC", 2,13}, {0xD7,"SMB5",2,11}, {0xD8,"CLD", 1, 8}, {0xD9,"CMP", 3, 4}, {0xDA,"PHX", 1, 8}, {0xDB,"", 0, 0}, {0xDC,"", 0, 0}, {0xDD,"CMP", 3, 3}, {0xDE,"DEC", 3, 3}, {0xDF,"BBS5",3,10}, {0xE0,"CPX", 2, 7}, {0xE1,"SBC", 2,12}, {0xE2,"", 0, 0}, {0xE3,"", 0, 0}, {0xE4,"CPX", 2,11}, {0xE5,"SBC", 2,11}, {0xE6,"INC", 2,11}, {0xE7,"SMB6",2,11}, {0xE8,"INX", 1, 8}, {0xE9,"SBC", 2, 7}, {0xEA,"NOP", 1, 8}, {0xEB,"", 0, 0}, {0xEC,"CPX", 3, 1}, {0xED,"SBC", 3, 1}, {0xEE,"INC", 3, 1}, {0xEF,"BBS6",3,10}, {0xF0,"BEQ", 2, 9}, {0xF1,"SBC", 2,16}, {0xF2,"SBC", 2,15}, {0xF3,"", 0, 0}, {0xF4,"", 0, 0}, {0xF5,"SBC", 2,13}, {0xF6,"INC", 2,13}, {0xF7,"SMB7",2,11}, {0xF8,"SED", 1, 8}, {0xF9,"SBC", 3, 4}, {0xFA,"PLX", 1, 8}, {0xFB,"", 0, 0}, {0xFC,"", 0, 0}, {0xFD,"SBC", 3, 3}, {0xFE,"INC", 3, 3}, {0xFF,"BBS7",3,10} };  

 

pass1はデータファイルを1文字ずつ読みながら、スキップ範囲指定されていなければR65C02dopcode.hを参照して該当するopcodeを見つけ、そのオペランドがアドレスであったらL_xxxx（xxxxはアドレス）というラベル名でラベルテーブルに格納するという作業を繰り返します。（スキップ範囲指定されている場合は下記の処理をします。）

従って、上記のaやzpはそのアドレスにラベルが付き、rは相対アドレスを絶対アドレスに変換したアドレスにラベルが付くことになります。

該当する命令が存在しない場合はエラーにはせずにそのコードをスキップします。（pass2で処理します。）

スキップ範囲の処理

スキップ範囲に指定したデータの扱いですが、範囲の先頭の1バイトの値がアスキー表示可能（$20～$7F）ならその範囲全体をFCC /abc.../のように表示し、そうでない場合はFCB $xx,$yy,$zz,...のように表示します。

【ここまでの結果】 ... 05Coding-pass1