Fill the sign-dependent params of the conv structure in case of unsigned 
    conversion
    @param conv: the structure to be filled

def _get_unsigned_params(conv):
    """
    Fill the sign-dependent params of the conv structure in case of unsigned 
    conversion
    @param conv: the structure to be filled
    """
    conv["sign_mask"] = 0
    conv["int_min"] = 0
    conv["int_mask"] = sum([2 ** i for i in range(conv["bin_point"], 
        conv["bits"])])
    conv["int_max"] = sum([2 ** i for i in range(conv["bits"] -
        conv["bin_point"])])