def rtt_get_num_down_buffers(self):
        """After starting RTT, get the current number of down buffers.
        Args:
          self (JLink): the ``JLink`` instance

        Returns:
          The number of configured down buffers on the target.

        Raises:
          JLinkRTTException if the underlying JLINK_RTTERMINAL_Control call fails.
        """
        cmd = enums.JLinkRTTCommand.GETNUMBUF
        dir = ctypes.c_int(enums.JLinkRTTDirection.DOWN)
        return self.rtt_control(cmd, dir)