code: def start(self):
          
          self._useV2 = self.cf.platform.get_protocol_version() >= 4
  
          logger.debug('[%d]: Using V2 protocol: %d', self.port, self._useV2)
  
          logger.debug('[%d]: Start fetching...', self.port)
          # Register callback in this class for the port
          self.cf.add_port_callback(self.port, self._new_packet_cb)
  
          # Request the TOC CRC
          self.state = GET_TOC_INFO
          pk = CRTPPacket()
          pk.set_header(self.port, TOC_CHANNEL)
          if self._useV2:
              pk.data = (CMD_TOC_INFO_V2,)
              self.cf.send_packet(pk, expected_reply=(CMD_TOC_INFO_V2,))
          else:
              pk.data = (CMD_TOC_INFO,)
              self.cf.send_packet(pk, expected_reply=(CMD_TOC_INFO,))
docs: Initiate fetching of the TOC.