Data reception device
A data reception device includes: an equalizer circuit that shapes a waveform of an input signal according to a set gain value; a CDR circuit which recovers a plurality of clock signals having different phases in one cycle from the input signal after being subjected to the waveform shaping performed by the equalizer circuit; an oversampler which performs sampling of the waveform-shaped input signal in synchronization with the plurality of clock signals and recovers a plurality of input data from the waveform-shaped input signal; and a calibration control unit which determines whether the oversampler correctly recovers the input data based on a result of the sampling performed by the oversampler, and generates a control signal to set the gain value of the equalizer circuit based on a determination result when it is determined that the input data is not correctly recovered.
1. A data reception device comprising:
an equalizer circuit which shapes a waveform of an input signal according to a set gain value;
a CDR circuit which recovers a plurality of clock signals having different phases in one cycle from the input signal after being subjected to the waveform shaping performed by the equalizer circuit during a calibration operation and recovers one clock signal from the input signal after being subjected to the waveform shaping performed by the equalizer circuit during a normal operation;
an oversampler which performs multiple sampling of the waveform-shaped input signal in synchronization with the plurality of clock signals at once and recovers a plurality of input data from the waveform-shaped input signal during the calibration operation;
a calibration control unit which determines whether the oversampler correctly recovers the input data based on a result of the sampling performed by the oversampler, and generates a control signal to set the gain value of the equalizer circuit based on a determination result when it is determined that the input data is not correctly recovered during the calibration operation; and
a skew adjustment circuit which adjusts a shift amount between a phase of the input signal after being subjected to the waveform shaping performed by the equalizer circuit and a phase of the one clock signal recovered by the CDR circuit during the normal operation,
wherein the calibration control unit decides a predetermined phase based on the result of the sampling performed by the oversampler and sends control information on the predetermined phase to the skew adjustment circuit, and
the skew adjustment circuit adjusts the phase of the one clock signal recovered by the CDR circuit so as to match the predetermined phase of the control information received from the calibration control unit.
2. The data reception device according to claim 1 , wherein
the CDR circuit has a voltage-controlled oscillation circuit having a loop circuit in which a plurality of logic inversion elements are connected in series, and
the voltage-controlled oscillation circuit outputs the plurality of clock signals having different phases in one cycle.
3. The data reception device according to claim 2 , wherein
the oversampler includes:
a clock selector, which is connected to the plurality of logic inversion elements and activates any one of the plurality of logic inversion elements to receive input of a clock signal; and
a flip-flop which is connected to the equalizer circuit and the clock selector.
4. The data reception device according to claim 2 , wherein
the oversampler includes a plurality of flip-flops connected to each of the equalizer circuit and the plurality of logic inversion elements.
5. The data reception device according to claim 2 , wherein
the oversampler includes a clock selector, which receives input of the clock signal via a delay device connected to the voltage-controlled oscillation circuit, and a flip-flop which is connected to the equalizer circuit and the clock selector.
6. The data reception device according to claim 1 , wherein
the calibration control unit is caused to generate the control signal to set the gain value of the equalizer circuit based on the determination result when it is determined that the oversampler is not correctly recovered the input data by periodically shifting to the calibration operation even after the calibration operation is shifted to the normal operation.