Patent ID: 8560875

Claim:
An apparatus for clock calibration on a remote device, the apparatus comprising: a first oscillator to generate a first clock signal during an active communication mode of the remote device to facilitate communications between the remote device and a host device, wherein the first oscillator is inactive during a sniff mode of the remote device; a second oscillator to generate a second clock signal during both the active communication and sniff modes, wherein the second oscillator consumes less power than the first oscillator; and a clock calibration module coupled to the first and second oscillators, the clock calibration module to: generate an estimated count for the first clock signal approximately at a transition from the sniff mode to the active communication mode, wherein the estimated count for the first clock signal is based on a clock ratio of a baseline count of the first clock signal relative to a baseline count of the second clock signal; calculate a difference between the estimated count for the first clock signal and an actual count from the host device to determine whether to update the clock ratio; forego updating the clock ratio in response to a determination that an incremental count of the second clock signal approximately during the sniff mode is less than a threshold amount; and update the clock ratio , according to the following algorithm: Δ ⁡ ( t ⁢ ⁢ 01 - t ⁢ ⁢ 00 ) = Δ ⁢ ⁢ T ⁢ ( t ⁢ ⁢ 11 - t ⁢ ⁢ 10 ) ( t ⁢ ⁢ 12 - t ⁢ ⁢ 11 ) , in which Δ(t 01 −t 00 ) represents an adjustment amount applied to the baseline count of the first clock signal, ΔT represents a calibration factor which is the difference between the estimated count for the first clock signal and the actual count from the host device, (t 11 −t 10 ) represents the baseline count of the second clock signal, and (t 12 −t 11 ) represents the incremental count of the second clock signal approximately during the sniff mode.