public function confStopBits($length)
    {
        if ($this->_dState !== SERIAL_DEVICE_SET) {
            trigger_error("Unable to set the length of a stop bit : the " .
                          "device is either not set or opened", E_USER_WARNING);

            return false;
        }

        if ($length != 1
                and $length != 2
                and $length != 1.5
                and !($length == 1.5 and $this->_os === "linux")
        ) {
            trigger_error(
                "Specified stop bit length is invalid",
                E_USER_WARNING
            );

            return false;
        }

        if ($this->_os === "linux") {
            $ret = $this->_exec(
                "stty -F " . $this->_device . " " .
                    (($length == 1) ? "-" : "") . "cstopb",
                $out
            );
        } elseif ($this->_os === "osx") {
            $ret = $this->_exec(
                "stty -f " . $this->_device . " " .
                    (($length == 1) ? "-" : "") . "cstopb",
                $out
            );
        } else {
            $ret = $this->_exec(
                "mode " . $this->_winDevice . " STOP=" . $length,
                $out
            );
        }

        if ($ret === 0) {
            return true;
        }

        trigger_error(
            "Unable to set stop bit length : " . $out[1],
            E_USER_WARNING
        );

        return false;
    }