The Bluetooth Clock,

Every Bluetooth unit has an internal system clock, which determines the timing and hopping of the transceiver. The Bluetooth clock is derived from a free running native
clock, which is never adjusted and is never turned off. For synchronization with other
units, only offsets are used. These offsets, when added to the native clock, provide
temporary Bluetooth clocks, which are mutually synchronized. The Bluetooth clock has
no relation to the time of day and can therefore be initialized to any value. The Bluetooth clock provides the heart beat of the Bluetooth transceiver. Its resolution is at least half the TX or RX slot length, or 312.5 µs. The Bluetooth clock has a cycle of about a day. If the clock is implemented with a counter, a 28-bit counter is required that wraps around at 2 28 -1. The LSB ticks in units of 312.5 µs, giving a clock rate of 3.2 KHz