A system for communicating information between circuits is described. A transmit circuit provides pulse-amplitude-modulation (PAM) signals via a communication channel to a receiver. A circuit in the receiver determines digital values from the received signals using a time-varying threshold voltage, which varies during the bit-time. This approach may compensate for inter-symbol interference (ISI) to increase the voltage and timing margins of the system.

In one example, an apparatus includes an offset tunable edge slicer having an input to receive a pulse amplitude modulation signal. The offset tunable edge slicer also has a plurality of possible offset settings corresponding to a plurality of different reference voltages of the offset tunable edge slicer. A multiplexer has an output coupled to the input of the offset tunable edge slicer and an input to receive a control signal that selects one of the plurality of possible offset settings for the offset tunable edge slicer. A phase detector has an input coupled to an output of the offset tunable edge slicer.

In a PAM-N receiver, sampler reference levels, DC offset and AFE gain may be jointly adapted to achieve optimal or near-optimal boundaries for the symbol decisions of the PAM-N signal. For reference level adaptation, the hamming distances between two consecutive data samples and their in-between edge sample are evaluated. Reference levels for symbol decisions are adjusted accordingly such that on a data transition, an edge sample has on average, equal hamming distance to its adjacent data samples. DC offset may be compensated to ensure detectable data transitions for reference level adaptation. AFE gains may be jointly adapted with sampler reference levels such that the difference between a reference level and a pre-determined target voltage is minimized

A method for adaptive coding and modulation. The method includes generating a set of mapping functions and transmitting a t.sup.th set of transmit symbols where 1≤t≤T and T is a maximum number of symbol transmissions. Transmitting the t.sup.th set of transmit symbols includes transmitting each transmit symbol in the t.sup.th set of transmit symbols. Each transmit symbol is transmitted by a respective transmitter. Transmitting each transmit symbol includes generating a t.sup.th set of mapped symbols, generating each transmit symbol from the t.sup.th set of mapped symbols, and transmitting each transmit symbol. Generating the t.sup.th set of mapped symbols includes applying a mapping functions subset of the set of mapping functions on a respective data vector. Each mapping function in the mapping functions subset depends on a respective mapped symbol in an r.sup.th set of mapped symbols where 0≤r≤T.

A circuit for receiving serial data. In some embodiments, the circuit has an input for receiving an analog input signal, and includes a first sampler for sampling the analog input signal relative to a first reference voltage, a second sampler for sampling the analog input signal relative to a second reference voltage, and a reference voltage control circuit. The second reference voltage may have a sign opposite to that of the first reference voltage; and the reference voltage control circuit may be configured to adjust the first reference voltage or the second reference voltage, based on a first sample of the analog input signal, the first sample having been taken at a sampling time corresponding to a one bit, in the serial data, preceded by a one bit and followed by a one bit.

The present disclosure relates to an adaptation method for data level (dLev) or data swing detection in a high-speed link system for multi-level (e.g. PAM-4) signaling. Provided are a receiver and a receiving method in which when a swing range of data received as an input is changed according to a channel condition, reference levels of data/swing detection samplers are not adaptively controlled, but the reference levels are fixed and a variable gain amplifier (VGA) is adaptively controlled for response to the change. Through the present disclosure, offset calibration of the data/swing detection samplers is more accurately performed and lower bit error rate (BER) is thus achieved.

In a PAM-N receiver, sampler reference levels, DC offset and AFE gain may be jointly adapted to achieve optimal or near-optimal boundaries for the symbol decisions of the PAM-N signal. For reference level adaptation, the hamming distances between two consecutive data samples and their in-between edge sample are evaluated. Reference levels for symbol decisions are adjusted accordingly such that on a data transition, an edge sample has on average, equal hamming distance to its adjacent data samples. DC offset may be compensated to ensure detectable data transitions for reference level adaptation. AFE gains may be jointly adapted with sampler reference levels such that the difference between a reference level and a pre-determined target voltage is minimized.

A clock recovery device (10), including: a signal conversion circuit (20) that sequentially converts two consecutive symbols of a 2n+1 value (n is a natural number) pulse amplitude modulation signal to one symbol of an NRZ (Non Return to Zero) signal; and a clock recovery circuit (30) that generates a recovery clock signal from the NRZ signal converted by the signal conversion circuit. The signal conversion circuit converts the two consecutive symbols: to 0, when a second symbol is n−1 or less; to 1, when the second symbol is n+1 or more; to 0, when a first symbol is n−1 or less and the second symbol is n; to 1, when a first symbol is n+1 or more and the second symbol is n; to a conversion result of previous two symbols, when both of the two consecutive symbols are n.

A method for adaptive coding and modulation. The method includes generating a set of mapping functions and transmitting a t.sup.th set of transmit symbols where 1≤t≤T and T is a maximum number of symbol transmissions. Transmitting the t.sup.th set of transmit symbols includes transmitting each transmit symbol in the t.sup.th set of transmit symbols. Each transmit symbol is transmitted by a respective transmitter. Transmitting each transmit symbol includes generating a t.sup.th set of mapped symbols, generating each transmit symbol from the t.sup.th set of mapped symbols, and transmitting each transmit symbol. Generating the t.sup.th set of mapped symbols includes applying a mapping functions subset of the set of mapping functions on a respective data vector. Each mapping function in the mapping functions subset depends on a respective mapped symbol in an r.sup.th set of mapped symbols where 0≤r≤T.

In a PAM-N receiver, sampler reference levels, DC offset and AFE gain may be jointly adapted to achieve optimal or near-optimal boundaries for the symbol decisions of the PAM-N signal. For reference level adaptation, the hamming distances between two consecutive data samples and their in-between edge sample are evaluated. Reference levels for symbol decisions are adjusted accordingly such that on a data transition, an edge sample has on average, equal hamming distance to its adjacent data samples. DC offset may be compensated to ensure detectable data transitions for reference level adaptation. AFE gains may be jointly adapted with sampler reference levels such that the difference between a reference level and a pre-determined target voltage is minimized.