protected override void Parse(AsmParser parser)
{
Register = parser.ReadRegW24();
parser.ReadToken(TokenType.Comma);
Token exprToken;
var imm = parser.CalculateExpression(out exprToken);
if (imm > 63) {
throw new TokenException("value must be less than 64", exprToken);
}
Value = (byte)imm;
}