| 摘要 |
This invention is a remotely controllable clock circuit embodied in a single integrated circuit device. The clock circuit includes at least one externally writable clock control register, a reference clock input, a controllable oscillator circuit, a pre-scalar circuit and a comparison circuit. The comparison circuit controlling the frequency of the controllable oscillator circuit to achieve a frequency match between a pre-scaled reference clock signal and a pre-scaled oscillator clock signal. The pre-scale divide factors are stored in respective fields in the clock control register. The clock control register may be memory mapped into a device memory space, accessed via an indirect access register or accessed via a serial scan chain. A trace first-in-first-out buffer has an input for trace data operating under the function clock signal of the operating circuits and an output operating under the oscillator clock signal.
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