public void Zero_is_not_less_than_zero()
{
// Act
var equalsZero = Arithmetics.IsLessThanZero(new Byte2(0));
// Assert
equalsZero.Should().BeFalse();
}
public void Minvalue_is_less_than_zero()
{
// Act
var equalsZero = Arithmetics.IsLessThanZero(new Byte2(short.MinValue));
// Assert
equalsZero.Should().BeTrue();
}
public void Minus_one_is_less_than_zero()
{
// Act
var equalsZero = Arithmetics.IsLessThanZero(new Byte2(-1));
// Assert
equalsZero.Should().BeTrue();
}
public void Maxvalue_is_not_less_than_zero()
{
// Act
var byte2 = new Byte2(short.MaxValue);
var equalsZero = Arithmetics.IsLessThanZero(byte2);
// Assert
equalsZero.Should().BeFalse();
}
/// <summary>
/// Bit 15 of the input indicates the kind of instruction:
/// Bit 15 | Instruction kind
/// -------+-----------------
/// 0 | data
/// 1 | computation
///
/// For a data instruction, W(data word) should reflect the input, the a flag should be 1 and all other flags should be 0.
/// For a computation instruction, the ci(computation instruction) flag should be 1, W should be 0. All other flags should be mapped from the bits in the input as follows:
/// Input Output
/// Bit Group flag
/// 14 (ignored) -
/// 13 (ignored) -
/// 12 source sm
/// 11 computation zx
/// 10 computation nx
/// 9 computation zy
/// 8 computation ny
/// 7 computation f
/// 6 computation no
/// 5 destination a
/// 4 destination d
/// 3 destination* a
/// 2 condition gt
/// 1 condition eq
/// 0 condition lt
/// </summary>
/// <param name="instruction"></param>
/// <returns></returns>
public static DecodedInstruction Decode(Byte2 instruction)
{
var isNegative = Arithmetics.IsLessThanZero(instruction);
var inverted = Gates.Invert(isNegative);
var s = Select16.Do(inverted, new Byte2(0), instruction);
var instructionOrZero = Select16.Do(isNegative, new Byte2(0), instruction);
return(new DecodedInstruction(isNegative,
s.Twelve,
new Operation(s.Eleven, s.Ten, s.Nine, s.Eight, s.Seven, s.Six),
new Destination(Gates.Or(inverted, s.Five), s.Four, s.Three),
new Condition(s.Two, s.One, s.Zero),
instructionOrZero));
}
public static bool Evaluate(Condition condition, Byte2 data)
{
var isLessThanZero = Arithmetics.IsLessThanZero(data);
var andIsLessThanZero = Gates.And(condition.LessThanZero, isLessThanZero);
var equalsZero = Arithmetics.EqualsZero(data);
var andIsEqualToZero = Gates.And(condition.EqualToZero, equalsZero);
var isGreaterThanZero = Gates.And(condition.GreaterThanZero,
Gates.And(Gates.Invert(isLessThanZero),
Gates.Invert(equalsZero)));
var lessOrEqual = Gates.Or(andIsLessThanZero, andIsEqualToZero);
var lessOrEqualOrGreater = Gates.Or(lessOrEqual, isGreaterThanZero);
return(lessOrEqualOrGreater);
}