Clock system
First Claim
1. A clock system for providing a system clock signal at a clock output, when enabled, for use by a processing unit, the clock system being enabled in response to a wake up signal provided by the processing unit, the clock system comprising:
- first oscillator circuit being enabled in response to the wake up signal to provide a first clock signal at an output;
second oscillator circuit comprising a PLL and an oscillator, the second oscillator circuit when enabled providing a second clock signal and a lock signal at first and second outputs respectively when the PLL is locked;
control circuitry coupled to the output of the first oscillator circuit and to the first and second outputs of the second oscillator circuit for coupling the first clock signal to the clock output to provide the system clock signal or for coupling the second clock signal and not the first clock signal to the clock output to provide the system clock signal when the control circuitry receives the lock signal.
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Accused Products
Abstract
A clock system (2) for providing a system clock signal at a clock output (4) for use by a processing unit comprises a first oscillator circuit (6) which is enabled in response to a wake up signal provided by the processing unit to provide a first clock signal (RINGO CLOCK) at an output, and a second oscillator circuit (8) comprising a PLL (14) and an oscillator (16). The second oscillator (8) circuit provides a second clock signal (PLL CLOCK) and a lock signal (LOCKED) at first and second outputs respectively when the PLL is locked. The clock system (2) further comprises control circuitry (10) coupled to the output of the first oscillator circuit (6) and to the first and second outputs of the second oscillator circuit (8) for coupling the first clock signal (RINGO CLOCK) to the clock output (4) to provide the system clock signal or when the control circuitry (10) receives the lock signal (LOCKED) for coupling the second clock signal (PLL CLOCK) and not the first clock signal (RINGO CLOCK) to the clock output (4) to provide the system clock signal.
56 Citations
7 Claims
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1. A clock system for providing a system clock signal at a clock output, when enabled, for use by a processing unit, the clock system being enabled in response to a wake up signal provided by the processing unit, the clock system comprising:
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first oscillator circuit being enabled in response to the wake up signal to provide a first clock signal at an output; second oscillator circuit comprising a PLL and an oscillator, the second oscillator circuit when enabled providing a second clock signal and a lock signal at first and second outputs respectively when the PLL is locked; control circuitry coupled to the output of the first oscillator circuit and to the first and second outputs of the second oscillator circuit for coupling the first clock signal to the clock output to provide the system clock signal or for coupling the second clock signal and not the first clock signal to the clock output to provide the system clock signal when the control circuitry receives the lock signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification