Bluetooth Clocks

Every Bluetooth unit has an internal system clock that determines the

timing and hopping of the transceiver. The Bluetooth clock is derived

from a free running native clock that is never adjusted and is never turned

off. For synchronization with other units, only offsets are used that,

added to the native clock, provide temporary Bluetooth clocks which

are mutually synchronized. The Bluetooth clock has no relation to the

time of day. The Bluetooth clock is very important for the Bluetooth

transceiver as it is involved in timing a number of important events without

which communication is not possible. Its resolution is at least half the

TX or RX slot length, or 312.5 microseconds. The 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 228 -1. The LSB ticks in

units of 312.5 microseconds, giving a clock rate of 3.2 kHz.