Clock Selection for a Communications Processor having a Sleep Mode

Abstract

A clock selector operative on two clocks operating on different domains and responsive to a SELECT input provides a transition from a first clock to a second clock, and from a second clock to a first clock with a dead zone therebetween. The delay is provided by a doublet register having a first register coupled to a second register, the two registers operative on one of the clock domains. Additionally, a clock selector is operative on two clocks which are each accompanied by a clock availability signal where the state machine provides a variety of states to create a dead zone between selections, and to bring the state machine to a known state until a clock signal is again available.

Description

FIELD OF THE INVENTION[0001]The present invention relates to clock selection for communications systems having a sleep mode. In particular, the invention is directed to wireless communications systems having an accurate network clock, a low speed clock for a sleep mode, and a host clock for an operational mode.BACKGROUND OF THE INVENTION[0002]FIG. 1A shows a prior art communications system, which includes a System on a Chip (SoC) 110, typically comprising baseband processing for a wireless communications system, which is coupled to an RF Front End 112 which accepts signals from antenna 113, and performs the sequential operations of RF amplification, mixing to baseband using a local oscillator, and conversion to digital sampled signals using an analog to digital converter (ADC), and delivering these signals to the SoC 110 over interface 111. A transmit stream may be generated by SoC 110, which is provided to RF front end 112 as a baseband digital signal, which the RF front end 112 co...

AI Technical Summary

Problems solved by technology

One problem of power saving operations is the requirement for the SoC 110 to maintain any existing network connections, and create new connections as required, both operations which require the SoC 110 to come out of sleep mode periodically and check for any pending traffic to be received or transmitted before going back into a sleep mode, and to be able to do this in a manner which does not cause any network connections or requests to time out for failure to respond.

There are many drawbacks associated with the process of FIGS. 1A and 1B.

The latency in response from time 152 to time 154 followed by initialization until time 156 consumes additional time, during which interval the SOC has to be in a wake up mode prior to handling any actual requests, which also represents a power consumption inefficiency.

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