Icera, Inc.

Jon Mangnall

Peter Cumming

Pete Cumming

Graham Cunningham

A circuit and method for determining the frequency of a first oscillating reference signal generated by a first reference oscillator. The circuit comprises: a second reference oscillator arranged to generate a second oscillating reference signal having a known frequency, a boot memory storing boot code comprising clock configuration code, and a processor coupled to the boot memory and the second reference oscillator. The processor is arranged to execute the boot code from the boot memory upon booting, wherein when executed the clock configuration code operates the processor to determine the frequency of the first reference signal by reference to the second reference signal.

Clock configuration

A circuit comprising: clock circuitry for supplying a first faster clock signal to a first circuit portion and a second slower clock signal to a second circuit portion, and varying the relative frequency of the first and second clock signals. Synchronisation logic generates pulses which indicate when to transfer data between the first and second circuit portions. The clock circuitry generates a first control signal at a predetermined time in each cycle of the first clock signal prior to a predetermined edge, and a second control signal at a predetermined time in each cycle of the second clock signal prior to a predetermined edge. A change in the relative frequency is conditional on a coincidence of the first and second control signals. The synchronisation generates the pulses such that there is at least one cycle of the first clock signal between those pulses, and such that there is only one of those pulses per cycle of the second clock signal.

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Bristol, United Kingdom

Jon Mangnall