Oracle International Corporation

Jihong Min

Dawei Huang

Jianghui Su

Hongtao Zhang

Embodiments include systems and methods for using generalized pulse amplitude modulation (PAM-X) signaling with an at-rate not-return-to-zero (NRZ) clock data recovery (CDR) system. Some implementations include dual-mode signaling for an at-rate CDR (e.g., using standard NRZ signaling at lower operating frequencies and pseudo-NRZ signaling derived from PAM-X signaling at higher operating frequencies. Embodiments derive an apparent direction of signal transition from PAM-X signaling. The direction can be used to calculate pseudo-NRZ values. For example, when the PAM-X signal transitions in an upward direction, a pseudo-current NRZ value and a pseudo-previous NRZ value of '&#x2212;1' and '+1' can be generated, respectively. An at-rate NRZ CDR can use the pseudo-NRZ values and a derived error value to make an offset determination. The offset determination can then be used to offset a generated clock signal in the CDR system.

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Ann Arbor, MI, United States of America

Jihong Min