instr2string_ass(b1, b2)

function str = instr2string_ass(b1, b2)
%INSTR2STRING_ASS returns string representation of instruction
%   STR = INSTR2STRING_ASS(B1, B2) returns a string giving the assembly
%   language representation of the instruction made of bytes B1, B2. 

%   Copyright 2008 University of Sussex and David Young

% instrs = {@NOP @LOADA, @LOADI, @STORE, @MOVE, @ADDI, @ADDF, @ORBITS, @ANDBITS, ...
%     @XORBITS, @ROTBITS, @JUMP, @HALT, @LOADR, @STORER, @JUMPR};

[op, r, s, t] = decodeInstr(b1, b2);
switch op
    case 0
        if b1 == hex2dec('F') && b2 == hex2dec('FF')
            str = 'NOP';
        else
            str = '';
        end
    case 1
        str = ['MOV     [' dec2hex(b2, 2) '] -> R' dec2hex(r)];
    case 2
        str = ['MOV     ' dec2hex(b2, 2) ' -> R' dec2hex(r)];
    case 3
        str = ['MOV     R' dec2hex(r) ' -> [' dec2hex(b2, 2) ']'];
    case 4
        str = ['MOV     R' dec2hex(s) ' -> R' dec2hex(t)];
    case 5
        str = ['ADDI    R' dec2hex(s) ', R' dec2hex(t) ' -> R' dec2hex(r)];
    case 6
        str = ['ADDF    R' dec2hex(s) ', R' dec2hex(t) ' -> R' dec2hex(r)];
    case 7
        str = ['OR      R' dec2hex(s) ', R' dec2hex(t) ' -> R' dec2hex(r)];
    case 8
        str = ['AND     R' dec2hex(s) ', R' dec2hex(t) ' -> R' dec2hex(r)];
    case 9
        str = ['XOR     R' dec2hex(s) ', R' dec2hex(t) ' -> R' dec2hex(r)];
    case 10
        str = ['ROT     R' dec2hex(r) ', ' num2str(t)];
    case 11
        if r == 0
            str = ['JMP     ' dec2hex(b2, 2)];
        else
            str = ['JMPEQ   ' dec2hex(b2, 2) ', R' dec2hex(r)];
        end
    case 12
        str = 'HALT';
    case 13
        str = ['MOV     [R' dec2hex(t) '] -> R' dec2hex(s)];
    case 14
        str = ['MOV     R' dec2hex(s) ' -> [R' dec2hex(t) ']'];
    case 15
        if r == 0 && (s == 0 || s == 2 || s == 3)
            str = ['JMP     R' dec2hex(t)];
        else
            switch s
                case 0
                    test = 'EQ';
                case 1
                    test = 'NE';
                case 2
                    test = 'GE';
                case 3
                    test = 'LE';
                case 4
                    test = 'GT';
                case 5
                    test = 'LT';
                otherwise
                    test = '??';
            end
            str = ['JMP' test '   R' dec2hex(t) ',  R' dec2hex(r)];
        end
end
end