How timeslots are used

Transmission/reception takes place in timeslots that are only 625 mikroseconds in duration. The Master uses even-numbered slots to address each slave in turn, and each addressed slave has the opportunity to answer in the following odd-numbered timeslot. Or it can wait for it turn next time around. In addition to this, some timeslots are used for broadcasts and as logical channels for synchronization and other control signals. Thus, we get a rotating scheme, resembling the illustration above. The slot-numbering proceeds to a very high number; it takes about a day for the slot-numbering to start over again. The clock of the Master unit decides when these slots start and end, and the slaves will thus need to be very closely synchronized to this clock.

The Communications channels The hopping sequence is unique for each piconet, and is determined by the Bluetooth device address of the Master. The channel is divided into 625 µs long timeslots. They are cyclically numbered by the clock of the piconet Master. Bluetooth uses 5 Logical Channels: LC Channel (Link Control) Is mapped onto the packet header. Carries low-level link control information, like flow control. Is carried on every packet except in the ID packet, which has no header. LM Channel (Link Manager) Carries control information exchanged between the link managers of the master and slave(s). UA/UI Channels (User Asynchronous/Isochronous Data) Carries L2CAP transparent asynchronous user data.. May be transmitted in one or more baseband packets. US Channel (User Synchronous Data) Carries transparent synchronous user data. Is carried over the SCO link.

Multi-slot packets