MIPS rev.1 指令参数

由于MIPS各个版本之间的操作数会变，如果出现无法识别的情况

需要根据官方的MIPS instruction手册逐条核对，此处的版本为Rev.1

    //******MIPS-55*********//
    parameter   //SPECIAL OP LIST   5-0
                ADDU    =   'b100001,
                SUBU    =   'b100011,
                ADD     =   'b100000,
                SUB     =   'b100010,
                AND     =   'b100100,
                OR      =   'b100101,
                XOR     =   'b100110,
                NOR     =   'b100111,
                SLT     =   'b101010,
                SLTU    =   'b101011,
                SRL     =   'b000010,
                SRA     =   'b000011,
                SLL     =   'b000000,
                SLLV    =   'b000100,
                SRLV    =   'b000110,
                SRAV    =   'b000111,
                JR      =   'b001000,
                JALR    =   'b001001,
                MULT    =    'b011000,
                MULTU   =   'b011001,
                DIV     =   'b011010,
                DIVU    =   'b011011,
                MFHI    =   'b010000,
                MFLO    =   'b010010,
                MTHI    =   'b010001,
                MTLO    =   'b010011,
                BREAK   =   'b001101,
                SYSCALL =   'b001100,
                TEQ     =   'b110100,
                //SPECIAL 2 func
                CLZ        =   'b100000,
                MUL        =   'b000010,
                //REGIMM OP LIST 20-16
                BLTZ    =   'b00000,
                BGEZ    =   'b00001,
                //COP0 OP LIST
                ERET    =   'b011000,  //5-0&&25TH=1
                MFC0    =   'b00000,   //20-16
                MTC0    =   'b00100,
                //OPCODE FIELD  31-26
                ADDI    =   'b001000,
                ADDIU   =   'b001001,
                ANDI    =   'b001100,
                ORI     =   'b001101,
                XORI    =   'b001110,
                LW      =   'b100011,
                SW      =   'b101011,
                BEQ     =   'b000100,
                BNE     =   'b000101,
                BLEZ    =   'b000110,
                BGTZ    =   'b000111,
                SLTI    =   'b001010,
                SLTIU   =   'b001011,
                LUI     =   'b001111,
                J       =   'b000010,
                JAL     =   'b000011,
                LB      =   'b100000,//    Load Byte Function=6'h24
                LBU     =   'b100100,//    1Load Byte Unsigned
                LH      =   'b100001,//    Load high
                LHU     =   'b100101,//    Load High Unsigned
                SB      =   'b101000,//    Send Byte
                SH      =   'b101001,//    Send High

                SPECIAL =   'b000000,
                SPECIAL2=    'b011100,
                REGIMM  =   'b000001,
                COP0    =   'b010000;  

    //ALU OPCODE
    parameter   _ADDU   =   'b0000;    //r=a+b unsigned
    parameter   _ADD    =   'b0010;    //r=a+b signed
    parameter   _SUBU   =   'b0001;    //r=a-b unsigned
    parameter   _SUB    =   'b0011;    //r=a-b signed
    parameter   _AND    =   'b0100;    //r=a&b
    parameter   _OR     =   'b0101;    //r=a|b
    parameter   _XOR    =   'b0110;    //r=a^b
    parameter   _NOR    =   'b0111;    //r=~(a|b)

    parameter   _LUI    =   'b1000;    //r={b[15:0],16'b0}
    parameter   _SLT    =   'b1011;    //r=(a-b<0)?1:0 signed
    parameter   _SLTU   =   'b1010;    //r=(a-b<0)?1:0 unsigned
    parameter   _SRA    =   'b1100;    //r=b>>>a
    parameter   _SLL    =   'b1110;    //r=b<<a
    parameter   _SRL    =   'b1101;    //r=b>>a

    parameter    _SYSCALL =   'b1000,
                _BREAK    =   'b1001,
                _TEQ      =   'b1101;

    wire [:]  op        =  instr[:];
    assign      rs        =  instr[:];
    assign      rt        =  instr[:];
    assign      rd        =  instr[:];
    wire [:]  func      =  instr[:];

    wire [:]  shamt     =  instr[:];
    wire [:] imm       =  instr[:];
    wire [:] addr      =  instr[:];

    parameter   SIGN      =   'b1;
    parameter   UNSIGN    =   'b0;
    wire     imm_sign     =   (op==ANDI||op==ORI||op==XORI)?UNSIGN:SIGN;

    wire [:] shamt_ext =   {'b0,shamt};
    wire [:] imm_ext   =   imm_sign?{{(){imm[]}},imm}:{'b0,imm};

    reg  [:] load_data,clz_data;

    assign    waddr    =    (op==SPECIAL||op==SPECIAL2)?    rd:    (op==JAL)    ?'b11111:rt;