Abstract: A method and apparatus for evaluating and optimizing a signaling system is described. A pattern of test information is generated in a transmit circuit of the system and is transmitted to a receive circuit. A similar pattern of information is generated in the receive circuit and used as a reference. The receive circuit compares the patterns. Any differences between the patterns are observable. In one embodiment, a linear feedback shift register (LFSR) is implemented to produce patterns. An embodiment of the present disclosure may be practiced with various types of signaling systems, including those with single-ended signals and those with differential signals. An embodiment of the present disclosure may be applied to systems communicating a single bit of information on a single conductor at a given time and to systems communicating multiple bits of information on a single conductor simultaneously.

Abstract: A system and method are shown for generation of at least one reference voltage level in a bus system. A reference voltage generator on a current driver includes at least one reference voltage level, at least one control signal, and an active device. The active device is coupled to the at least one control signal, such as a current control signal, and a selected reference voltage of the at least one reference voltage level. The active device is arranged to shift the at least one reference voltage level based on the at least one current control signal such as an equalization signal, a crosstalk signal, or the combination thereof, employed on the current driver.

Abstract: A circuit, apparatus and method obtains system margin at the receive circuit using phase shifted data sampling clocks while allowing the CDR to remain synchronized with the incoming data stream in embodiments. In an embodiment, a circuit includes first and second samplers to sample a data signal and output data and edge information in response to a data clock signal and an edge clock signal. A phase detector generates phase information in response to the data information and the edge information. A clock phase adjustment circuit generates the data clock signal and the edge clock signal in response to the data information during a synchronization mode. The clock phase adjustment circuit increments a phase of the data clock signal during a waveform capture mode.

Abstract: A signaling system includes a pre-emphasizing transmitter and an equalizing receiver coupled to one another via a high-speed signal path. The receiver measures the quality of data conveyed from the transmitter. A controller uses this information and other information to adaptively establish appropriate transmit pre-emphasis and receive equalization settings, e.g. to select the lowest power setting for which the signaling system provides some minimum communication bandwidth without exceeding a desired bit-error rate.

Abstract: A memory system uses multiple pulse amplitude modulation (multi-PAM) output drivers and receivers to send and receive multi-PAM signals. A multi-PAM signal has more than two voltage levels, with each data interval now transmitting a “symbol” at one of the valid voltage levels. In one embodiment, a symbol represents two or more bits. The multi-PAM output driver drives an output symbol onto a signal line. The output symbol represents at least two bits that include a most significant bit (MSB) and a least significant bit (LSB). The multi-PAM receiver receives the output symbol from the signal line and determines the MSB and the LSB.

Abstract: A circuit, apparatus and method obtains system margin at the receive circuit using phase shifted data sampling clocks while allowing the CDR to remain synchronized with the incoming data stream in embodiments. In an embodiment, a circuit includes first and second samplers to sample a data signal and output data and edge information in response to a data clock signal and an edge clock signal. A phase detector generates phase information in response to the data information and the edge information. A clock phase adjustment circuit generates the data clock signal and the edge clock signal in response to the data information during a synchronization mode. The clock phase adjustment circuit increments a phase of the data clock signal during a waveform capture mode.

Abstract: A system and method are shown for generation of at least one reference voltage level in a bus system. A reference voltage generator on a current driver includes at least one reference voltage level, at least one control signal, and an active device. The active device is coupled to the at least one control signal, such as a current control signal, and a selected reference voltage of the at least one reference voltage level. The active device is arranged to shift the at least one reference voltage level based on the at least one current control signal such as an equalization signal, a crosstalk signal, or the combination thereof, employed on the current driver.

Abstract: A multi-tone system includes a data transmission circuit with an interface for receiving a data stream for transmission, a data steam splitter that splits the data stream to produce multiple substreams and a plurality of parallel data preparation circuits. Each data preparation circuit prepares a respective substream for transmission and generates a respective sub-channel signal. At least a first data preparation circuit of the plurality of parallel data preparation circuits includes a first analog filter for filtering a first substream. The first analog filter operates at a sample rate greater than the respective symbol rate of the first substream. The first analog filter provides pre-emphasis of the respective sub-channel signal and attenuation of signals outside of a respective band of frequencies corresponding to the respective sub-channel signal. The data transmission circuit also includes a combiner for combining respective sub-channel signals to generate a data transmission signal.

Abstract: A communication system utilizing an adjustable link has at least a first data transmission circuit including at least a first communication link circuit. The first communication link circuit has a baseband circuit and at least a passband circuit. The baseband circuit corresponds to a baseband sub-channel and the passband circuit corresponds to a passband sub-channel. The first communication link circuit also includes a circuit that distributes a first subset of a data stream having a first symbol rate to the baseband circuit and a second subset of the data stream having a second symbol rate to the passband circuit. The baseband sub-channel and the passband sub-channel are separated by an adjacent guardband of frequencies. The passband carrier frequency is adjusted to define the guardband and the guardband corresponds to a first notch in a channel response of a first communications channel.

Abstract: A system includes a first integrated circuit device and a second integrated circuit device. The first device transmits a data sequence to the second integrated circuit device, and the second device samples the data sequence to produce receiver data. The second device then transmits the receiver data back to the first device. Within the first integrated circuit device, a comparison between the data sequence and the receiver data is performed, and based on the comparison, the first device generates information representative of a calibrated timing offset. The first device uses the information representative of the calibrated timing offset to adjust timing associated with transferring write data from the first integrated circuit to the second integrated circuit.

Abstract: An apparatus and method for receiving high-speed signals having a wide common-mode range with low input-to-output latency. In one embodiment, the receiver includes an integrator to accumulate charge in accordance with an input signal during an integration time interval to produce an output voltage. A sense amplifier samples and converts the output voltage of the integrator to a logic signal; and a latch stores the logic signal. In an alternate embodiment, a preamplifier conditions the input signal prior to being integrated. In another embodiment using multiple receivers, circuitry is added to the receiver to compensate for timing errors associated with the distribution of the timing signals. In yet another embodiment, the integrator is coupled to an equalization circuit that compensates for intersymbol interference. In another embodiment, another circuit compensates for accumulated voltage offset errors in the integrator.

Abstract: A method and circuit for achieving minimum latency data transfer between two mesochronous (same frequency, different phase) clock domains is disclosed. This circuit supports arbitrary phase relationships between two clock domains and is tolerant of temperature and voltage shifts after initialization while maintaining the same output data latency. In one embodiment, this circuit is used on a bus-system to re-time data from receive-domain, clocks to transmit-domain clocks. In such a system the phase relationships between these two clocks is set by the device bus location and thus is not precisely known. By supporting arbitrary phase resynchronization, this disclosure allows for theoretically infinite bus-length and thus no limitation on device count, as well as arbitrary placement of devices along the bus. This ultimately allows support of multiple latency-domains for very long buses.

Abstract: Described are methods and circuits for reducing the error-inducing effects of crosstalk. Communication circuits in accordance with some embodiments adjust the phase of transmitted “aggressor” data to misalign transmitted signals from the perspective of “victim” channels. This misalignment moves the noise artifacts cross coupled to the victim channel away from sensitive sample times in the victim data, and consequently reduces the net effects of aggressor crosstalk on neighboring victim channels. Some embodiments reduce the effects of crosstalk by introducing static timing offsets to one or a plurality of aggressor transmitters, one or a plurality of victim transmitters, or some combination of aggressor and victim transmitters. Other embodiments dynamically alter the relative timing of aggressor and victim transmitters.

Abstract: An integrated circuit device is described. The integrated circuit device includes a transmitter circuit having an output driver to output data, and a register to store a value representative of an equalization co-efficient setting of the output driver. The value may be determined based on information stored in a supplemental memory device.

Abstract: Bus communications are optimized by adjusting signal characteristics in accordance with one or more topography dependent parameters. In a bus transmitter, a transmit signal characteristic is adjusted in accordance with a topography dependent parameter. A port in the bus transmitter receives the topography dependent parameter for later use by the parameter adjustment circuitry. The parameter adjustment circuitry adjusts a parameter control signal in accordance with the topography dependent parameter, which is coupled to the output driver. Prior to driving an output signal onto a bus, the output driver adjusts the transmit signal characteristic in accordance with the parameter control signal. Similarly, in a bus receiver, a receive signal characteristic is adjusted in response to a topography dependent parameter.

Abstract: A receive circuit for receiving a signal transmitted via an electric signal conductor. A first sampling circuit generates a first sample value that indicates whether the signal exceeds a first threshold level, and a second sampling circuit generates a second sample value that indicates whether the signal exceeds a second threshold level. A first select circuit receives the first and second sample values from the first and second sampling circuits and selects, according to a previously generated sample value, either the first sample value or the second sample value to be output as a selected sample value.

Abstract: Provided are a method and apparatus for high-speed, multi-mode PAM symbol transmission. A multi-mode PAM output driver drives one or more symbols, the number of levels used in the PAM modulation of the one or more symbols depending on the state of a PAM mode signal. Additionally, the one or more symbols are driven at a symbol rate, the symbol rate selected in accordance with the PAM mode signal so that a data rate of the driven symbols in constant with respect to changes in the state of the PAM mode signal. Further provided are methods for determining the optimal number of PAM levels for symbol transmission and reception in a given physical environment.

Abstract: A technique for receiving differential multi-PAM signals is disclosed. In one particular exemplary embodiment, the technique may be realized as a differential multi-PAM extractor circuit. In this particular exemplary embodiment, the differential multi-PAM extractor circuit comprises an upper LSB sampler circuit configured to receive a differential multi-PAM input signal and a first differential reference signal, and to generate a first differential sampled output signal. The differential multi-PAM extractor circuit also comprises a lower LSB sampler circuit configured to receive the differential multi-PAM input signal and a second differential reference signal, and to generate a second differential sampled output signal.

Abstract: A method and apparatus for evaluating and calibrating a signaling system is described. Evaluation is accomplished using the same circuits actually involved in normal operation of the signaling system. Capability for in-situ testing of a signaling system is provided, and information may be obtained from the actual perspective of a receive circuit in the system. A pattern of test information is generated in a transmit circuit of the system and is transmitted to a receive circuit. A similar pattern of information is generated in the receive circuit and used as a reference. The receive circuit compares the patterns. Any differences between the patterns are observable. Preferably, the patterns are repeating patterns that allow many iterations of testing to be performed. In one embodiment, a linear feedback shift register (LFSR) is implemented to produce patterns.

Abstract: A technique for utilizing spare bandwidth resulting from the use of a code in a multi-level signaling system is disclosed. In one particular exemplary embodiment, the technique may be realized as a method for utilizing spare bandwidth resulting from the use of a code in a multi-level signaling system, wherein the code has a characteristic wherein a signal transition is periodically unused. Such a method may comprise modifying the code such that the periodically unused signal transition is used to represent additional information.