Abstract: Signal detection circuitry for a serial interface oversamples the input—i.e., samples the input multiple times per clock cycle—so that the likelihood of missing a signal is reduced. Sampling may be done with a regenerative latch which has a large bandwidth and can latch a signal at high speed. The amplitude threshold for detection may be programmable, particularly in a programmable device. Thus, between the use of a regenerative latch which is likely to catch any signal that might be present, and the use of oversampling to avoid the problem of sampling at the wrong time, the likelihood of failing to detect a signal is greatly diminished. Logic, such as a state machine, may be used to determine whether the samples captured s do or do not represent a signal. That logic may be programmable, allowing a user to set various parameters for signal detection.

Abstract: A circuit includes a differential circuit that generates a differential output signal at first and second output nodes. The circuit also includes a first variable capacitor coupled to the first output node of the differential circuit, and a second variable capacitor coupled to the second output node of the differential circuit. A control circuit controls capacitances of the first and the second variable capacitors in response to a measurement of the differential output signal.

Abstract: A programmable logic device integrated circuit (“PLD”) includes high-speed serial interface (“HSSI”) circuitry in addition to programmable logic circuitry. The HSSI circuitry includes multiple channels of nominal data-handling circuitry (typically including clock and data recovery (“CDR”) circuitry), and at least one channel of nominal clock management unit (“CMU”) circuitry (typically including phase-locked loop (“PLL”) circuitry or the like). To increase the flexibility with which the channels can be used, the nominal data-handling channels are equipped to alternatively perform CMU-type functions, and the nominal CMU channel is equipped to alternatively perform data-handling functions.

Abstract: Methods and apparatus are provided for selectively setting a CM voltage for a transceiver, reducing the effect of current mismatch, and generating a voltage step that can be used for receiver detection. A circuit of the invention can include voltage generator circuitry operable to generate a plurality of voltage signals of substantially different voltages. The circuit can also include multiplexer circuitry with voltage inputs coupled to the voltage signals. The multiplexer circuitry can be operable to select a reference signal from among the voltage inputs. In addition, the circuit can include operational amplifier (“op-amp”) circuitry with a first input coupled to the reference signal and a second input coupled to an output signal of the op-amp circuitry.

Abstract: A programmable logic integrated circuit device has a plurality of regions of programmable logic disposed on the device in a plurality of intersecting rows and columns of such regions. Interconnection resources (e.g., interconnection conductors, signal buffers/drivers, programmable connectors, etc.) are provided on the device for making programmable interconnections to, from, and/or between the regions. At least some of these interconnection resources are provided in two forms that are architecturally similar (e.g., with similar and substantially parallel routing) but that have significantly different signal propagation speed characteristics. For example, a major or larger portion of such dual-form interconnection resources may have what may be termed normal signal speed, while a smaller minor portion may have significantly faster signal speed. Secondary (e.g.

Abstract: An oscillator circuit includes transistors that are cross-coupled through routing conductors in a first conductive layer. The oscillator circuit also includes a varactor, a capacitor, and an option conductor in a second conductive layer. The option conductor forms at least a portion of a connection between one of the transistors and the capacitor or the varactor.

Abstract: A transmitter that includes a first phase locked loop (PLL) and a second PLL coupled to the first PLL is described. In one implementation, the first PLL is an inductance-capacitance (LC) type PLL and the second PLL is a ring type PLL. Also, in one embodiment, the transmitter further includes a PLL selection multiplexer coupled to the first and second PLLs, where the PLL selection multiplexer receives an output of the first PLL and an output of the second PLL and outputs either the output of the first PLL or the output of the second PLL. In one implementation, a control signal for controlling selection by the PLL selection multiplexer is programmable at runtime. In one implementation, the transmitter of the present invention further includes a clock generation block coupled to the PLL selection multiplexer, a serializer block coupled to the clock generation block and a transmit driver block coupled to the serializer block.

Abstract: A programmable logic device (“PLD”) or the like has a plurality of data transmitter channels. Certain circuitry is shared by the channels. The shared circuitry includes at least one phase-locked loop (“PLL”) circuit for producing a primary clock signal, and global frequency divider circuitry for producing at least one global secondary clock signal based on the primary signal. The primary and global secondary signal(s) are distributed to the channels. Each of the channels includes local frequency divider circuitry for producing at least one local secondary clock signal based on the primary signal. Each channel also includes selection circuitry for selecting either the global or local secondary signal(s) for use by clock utilization circuitry of the channel. The clock utilization circuitry may include serializer circuitry for converting data from parallel to serial form.

Abstract: Transceiver circuitry on a programmable logic device integrated circuit (“PLD”) is preferably provided in a plurality of identical or at least similar modules. Each module preferably includes a plurality of transceiver channels and a clock source unit. Clock distribution circuitry is provided for distributing the signal of a module's clock source to all of the transceiver channels in that module, and also selectively beyond that module to other modules.

Abstract: A circuit includes a first area, a second area, and a third area. The second area includes a locked loop circuit that generates a clock signal. The locked loop circuit receives a supply voltage that is isolated from noise generated in the first area. The third area includes multiple quads of channels and a clock line coupled to route at least one clock signal generated in the second area to the channels in each of the quads. The third area is separate from the second area in the circuit.

Abstract: In a programmable logic device (PLD) having a plurality of serial interface channels, the number of adaptive dispersion compensation engines (ADCEs), which adjust the equalization of each channel that requires it, is reduced. In one embodiment, one ADCE is provided for every group of channels (e.g., every group of two channels), and multiplexers are provided to connect the ADCE to one channel (or more) according to the user logic design. In another embodiment, one ADCE is provided for every group of channels, and time-division multiplexing (TDM) is used to connect the ADCE sequentially to every channel in the group that requires it. Because the time required to adjust each channel is small, theoretically all ADCEs on the PLD could be considered one group, sharing one ADCE by TDM. The TDM circuitry could be programmable to allow priority to be given to certain channels, so that they are adjusted first.

Abstract: Signal offset variation caused by transistor variation/mismatch in integrated circuits may be reduced. In one embodiment, a buffer circuit has variable-valued circuit elements. Offset variation measurements are made and the variable-valued circuit elements are calibrated to reduce the measured offset variation. In another embodiment, each amplifying stage of a multi-stage buffer provides variable gain. The total DC gain of the cascade is distributed unevenly across the stages, with more DC gain being provided by amplifier stages at the beginning of the cascade than at the end. An additional pre-amplifier stage can also be provided at the beginning of the cascade.

Abstract: A programmable logic device is provided with adaptive equalization circuitry that is programmable in one or more respects. Examples of the programmable aspects of the equalization circuitry are (1) the number of taps used, (2) whether integer or fractional spaced taps are used, (3) what starting values are used in the computation of coefficient values, (4) whether satisfactory coefficient values are computed only once or on an on-going basis, (5) whether an error signal is generated using a decision directed algorithm or using a training pattern, (6) what training pattern (if any) is used, and/or (7) the location of the sampling point in the bit period of the signal to be equalized.

Abstract: An integrated circuit device such as a programmable logic device (“PLD”) includes a plurality of blocks of legacy circuitry. These legacy blocks leave at least one corner of the device unoccupied by such legacy circuitry. This at least one corner is used for relatively newly developed circuitry so as to simplify and speed the design of relatively new circuitry, to avoid having to significantly redesign any of the legacy circuitry to give the device the capabilities of the new circuitry, etc. The relatively newly developed circuitry may be high-speed serial data signal interface (“HSSI”) circuitry that is capable of operating at serial data rates faster than any legacy HSSI circuitry on the device.

Abstract: Equalization circuitry may be used to compensate for the attenuation of a data signal caused by a transmission medium. The control circuitry for the equalization circuitry may generate control inputs for equalization stages that control the amount of gain provided to the data signal. A comparator may determine whether the gain from the equalization circuitry is less than or more than the desired amount of gain. A programmable up/down counter may adjust the counter value based on the output of the comparator. The counter value may be converted into one or more analog voltages using one or more digital-to-analog converters. These analog voltages may be provided to the equalization stages as control inputs. The control circuitry may also include hysteresis circuitry that prevents the counter value from being adjusted when the gain produced by the equalization stages is close to the desired amount of gain.

Abstract: High-speed serial interface or transceiver circuitry on a programmable logic device integrated circuit (“PLD”) includes features that permit the PLD to satisfy a wide range of possible user needs or applications. This range includes both high-performance applications and applications in which reduced power consumption by the PLD is important. In the latter case, any one or more of various features can be used to help reduce power consumption.

Abstract: Systems and methods for adjusting a signal received from a communication path are disclosed. A receiver can receive a signal from a communication path which attenuates at least some frequency components of the signal. The receiver can include an equalization block that adjusts at least some of the frequency content of the received signal, a signal normalization block that provides a normalized signal amplitude and/or a normalized edge slope, and a control block. In one embodiment, the control block controls frequency adjustment in the equalization block for high frequencies. For low frequency adjustment, user-programmable parameters control the normalized signal amplitude in the signal normalization block and the low frequency adjustment in the equalization block.

Abstract: Systems and methods for adjusting a signal received from a communication path are disclosed. A receiver can receive a signal from a communication path which attenuates at least some frequency components of the signal. The receiver can include an equalization block that adjusts at least some of the frequency content of the received signal, a signal normalization block that provides a normalized signal amplitude and/or a normalized edge slope, and a control block. In one embodiment, the control block controls frequency adjustment in the equalization block for high frequencies but not for low frequencies. For low frequency adjustment, the control block controls the normalized signal amplitude in the signal normalization block. In this manner, controlled adjustment for low frequency content is performed in the signal normalization block.

Abstract: Methods and apparatus are provided for generating a clock signal with relatively high bandwidth and relatively low phase noise. A circuit of the invention can include a pair of transistors serially coupled between a signal of relatively high voltage and a source of relatively low voltage, where a voltage of the signal of relatively high voltage can vary according to a voltage of a variable control signal. A gate of one of the pair of transistors can be coupled to an input clock signal, and an output node between the pair of transistors can be coupled to an output clock signal. The circuit can also include a third transistor, whose drain and source are coupled to the output clock signal, and whose gate can be coupled to a gear input signal. This circuit can advantageously operate under at least two different gears, each with different bandwidth and phase noise characteristics.

Abstract: An integrated circuit capable of monitoring analog voltages inside an analog block is presented. The integrated circuit has an analog test multiplexer (mux) whose inputs are connected to analog voltages of interest inside an analog block. The analog test multiplexer directs a selected analog voltage from an analog block to the output of the analog test mux. The integrated circuit further includes an analog monitor state machine which provides the selection bits to the analog test multiplexer, enabling random access to the analog voltages inside the analog block. The integrated circuit also includes an analog to digital converter for converting the selected analog voltage from the analog test multiplexer into a digital representation.