/// <summary>
/// Conditional operand in the next-to-lowest nybble.
/// </summary>
private static bool c4(uint uInstr, C166Disassembler dasm)
{
var c = (CondCode)((uInstr >> 4) & 0xF);
dasm.ops.Add(new ConditionalOperand(c));
return(true);
}
private static bool rel(uint uInstr, C166Disassembler dasm)
{
var offset = relField.ReadSigned(uInstr) << 1;
var addr = dasm.rdr.Address + offset;
dasm.ops.Add(AddressOperand.Create(addr));
return(true);
}
public override C166Instruction Decode(uint wInstr, C166Disassembler dasm)
{
if (!dasm.rdr.TryReadLeUInt16(out ushort uHigh))
{
return(dasm.CreateInvalidInstruction());
}
wInstr |= ((uint)uHigh) << 16;
return(nextDecoder.Decode(wInstr, dasm));
}
private static bool trapNo(uint uInstr, C166Disassembler dasm)
{
if ((uInstr & 0x100) != 0)
{
return(false);
}
dasm.ops.Add(ImmediateOperand.Byte((byte)(uInstr >> 9)));
return(true);
}
/// <summary>
/// Direct 16-bit jump address.
/// </summary>
private static bool caddr(uint uInstr, C166Disassembler dasm)
{
if (!dasm.rdr.TryReadLeUInt16(out ushort uAddr))
{
return(false);
}
dasm.ops.Add(AddressOperand.Ptr16(uAddr));
return(true);
}
private static bool data16(uint uInstr, C166Disassembler dasm)
{
if (!dasm.rdr.TryReadLeUInt16(out ushort data))
{
return(false);
}
dasm.ops.Add(ImmediateOperand.Word16(data));
return(true);
}
private static bool pageNo(uint uInstr, C166Disassembler dasm)
{
if ((uInstr & 0x100) != 0)
{
return(false);
}
var page = ImmediateOperand.Word16((ushort)Bits.ZeroExtend(uInstr >> 16, 10));
dasm.ops.Add(page);
return(true);
}
/// <summary>
/// Register referred to twice in the high byte of the opcode.
/// </summary>
private static bool nn(uint uInstr, C166Disassembler dasm)
{
var regs = Registers.GpRegs;
var nReg = Bits.ZeroExtend(uInstr >> 12, 4);
var mReg = Bits.ZeroExtend(uInstr >> 8, 4);
if (nReg != mReg)
{
return(false);
}
dasm.ops.Add(new RegisterOperand(regs[nReg]));
return(true);
}
/// <summary>
/// Segment descriptor encoded in high byte of instruction.
/// </summary>
private static bool seg(uint uInstr, C166Disassembler dasm)
{
dasm.ops.Add(ImmediateOperand.Byte((byte)(uInstr >> 8)));
return(true);
}
private static bool data2_12(uint uInstr, C166Disassembler dasm)
{
dasm.ops.Add(ImmediateOperand.Byte((byte)((uInstr >> 12) & 0b11)));
return(true);
}