Abstract: Voltage controlled oscillator (VCO) circuitry with low phase noise and a wide range of operating frequencies is presented. The VCO circuitry includes circuitry with two or more VCO sub-circuits, each sub-circuit being optimized to produce output clock signals with low phase noise and with frequencies in a different range. Sub-circuits with gear inputs may be operative to produce output clock signals in a lower range of frequencies, while sub-circuits optimized for high speed operation may be used to produce output signals in a higher range of frequencies. A control circuit may be used to produce a control signal coupled to all sub-circuits. The control signal may set the operating frequency of the sub-circuits.

Abstract: Automatic rate negotiation logic for a high speed serial interface in a programmable logic device determines whether multiple occurrences of a single-bit transition (i.e., a data transition from “0” to “1” to “0” or from “1” to “0” to “1”) occur within a predetermined time interval on a data channel of a high-speed serial interface. The interval preferably is selected such that multiple occurrences of a single-bit transition mean that the data channel is operating in full-rate mode. The rate negotiation logic may share a phase detector with clock data recovery circuitry in the interface. The phase detector may be a bang-bang phase detector specially adapted to detect single-bit transitions.

Abstract: A programmable logic device (“PLD”) includes circuitry for optionally and variably modifying characteristics of an input signal in any of several respects. Examples of such modifications include AC coupling the signal into the PLD, low pass filtering the signal (with selectable low-pass filter corner frequency), shifting the common voltage of the input signal, and/or subjecting the input signal to a selectable amount of attenuation.

Abstract: The architecture of a programmable logic device (“PLD”) is modified in one or more of several respects to facilitate inclusion of high-speed serial interface (“HSSI”) circuitry in the PLD. For example, the HSSI circuitry is preferably located along one side of the device, taking the place of regular peripheral IO circuitry in that area. Certain portions of the core logic circuitry are modified to better interface with the HSSI circuitry.

Abstract: An oscillator circuit can generate a periodic signal, and a frequency adjustment circuit can adjust the frequency of the periodic signal. The periodic signal may include phase jitter. In one aspect of the invention, the phase jitter may be mitigated by connecting other circuitry to the oscillator circuit and allowing the other circuitry to draw current. In one embodiment, the other circuitry is connected in parallel with the oscillator circuit. In one embodiment, the other circuitry is configured to draw greater current to mitigate more phase jitter and to draw less current to mitigate less phase jitter. In one embodiment, a greater portion of the other circuitry is connected to the oscillator circuit for higher frequencies and a lesser portion of the other circuitry is connected to the oscillator circuit for lower frequencies.

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 are provided using dynamically adjustable differential output drivers. Integrated circuits such as programmable logic devices may be provided with adjustable differential output drivers for transmitting high-speed data to other integrated circuits. The peak-to-peak output voltage and common-mode voltage of the output drivers may be adjusted. Dynamic control circuitry may be used to control the settings of current sources, programmable resistors, and voltage source circuitry in the adjustable differential output driver automatically in real time. The adjustable components in the differential output driver may be adjusted by the dynamic control circuitry based on feedback information received from the integrated circuit to which the data is transmitted.

Abstract: A bias circuit includes a digital to analog converter (D2A) generating an output representing a voltage level for tuning an analog signal. The D2A is coupled to a primary register frame that includes a plurality of register frames that are serially linked. The bias circuit includes a decoder also coupled to the primary register frame. An output enable logic module is also included. The output enable logic module determines when the primary register has a complete data set as the data is shifted into the primary register frame from a memory region that may be a ROM, RAM, soft IP of a PLD, an intelligent host or tester serial data input stream. A method for adjusting a signal through a bias circuit is also provided.

Abstract: A digital controller for a voltage controlled oscillator (VCO) is provided within a phase lock loop (PLL). The digital controller includes a digital filter having first and second inputs for receiving upward and downward adjustment signals, respectively. The digital filter generates an increment signal and a decrement signal in response to the upward and downward adjustment signals, respectively. The digital controller includes a digital counter having first and second inputs for receiving the increment and decrement signals, respectively. The digital counter generates a multi-bit output signal that represents a running sum of the increment and decrement signals. The digital controller further includes a digital-to-analog converter (DAC) having an input for receiving the running sum output signal generated by the digital counter. The DAC is defined to generate a control voltage for the VCO in response to receipt of the running sum output signal from the digital counter.

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: Equalization of an incoming data signal can be controlled by sampling that signal at times when data values in that signal should be stable (“data samples”) and when that signal should be in transition between successive data values that are different (“transition samples”). A transition sample that has been taken between two successive differently valued data samples is compared to a reference value (which can be one of those two data samples). The result of this comparison can be used as part of a determination as to whether to increase or decrease equalization of the incoming data signal.

Abstract: Any number of transceiver channels is tested for jitter generation/tolerance simultaneously. Tested channels use a serial loopback path to connect a transceiver transmit channel to a transceiver receiver channel. Both the transmitter and receiver PLLs are connected to a common reference clock. The reference clock is modulated with jitter at a frequency below the bandwidth of the transmitter PLL but above the bandwidth of the receiver PLL. The magnitude of eye closure (in an eye diagram), which is equivalent to the amplitude of the jitter, is used to filter out bad transceiver units.

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: High-speed serial data transceiver circuitry on a programmable logic device (“PLD”) includes some channels that are able to operate at data rates up to a first, relatively low maximum data rate, and other channels that are able to operate at data rates up to a second, relatively high maximum data rate. The relatively low-speed channels are served by relatively low-speed phase locked loop (“PLL”) circuitry, and have other circuit components that are typically needed for handling data that is transmitted at relatively low data rates. The relatively high-speed channels are served by relatively high-speed PLLs, and have other circuit components that are typically needed for handling data that is transmitted at relatively high data rates.

Abstract: A programmable logic device has many regions of programmable logic, together with relatively general-purpose, programmable, interconnection resources that can be used to make interconnections between virtually any of the logic regions. In addition, various types of more local interconnection resources are associated with each logic region for facilitating the making of interconnections between adjacent or nearby logic regions without the need to use the general-purpose interconnection resources for those interconnections. The local interconnection resources support flexible clustering of logic regions via relatively direct and therefore high-speed interconnections, preferably in both horizontal and vertical directions in the typically two-dimensional array of logic regions. The logic region clustering options provided by the local interconnection resources are preferably boundary-less or substantially boundary-less within the array of logic regions.

Abstract: A bias circuit includes a digital to analog converter (D2A) generating an output representing a voltage level for tuning an analog signal. The D2A is coupled to a primary register frame that is one of a plurality of register frames forming a data chain. The plurality of register frames are serially linked and data within the data chain is shifted among the plurality of register frames. Through a time domain multiplexing scheme, the D2A can be shared by control knobs of the equalization circuit. The bias circuit includes a decoder also coupled to the primary register frame. An output enable logic module is also included. The output enable logic module determines when the primary register has a complete data set as the data within the data chain is shifting according to the clock period. A method for adjusting a signal through a bias circuit is also provided.

Abstract: Integrated circuit serializer circuitry is provided that converts parallel data to serial data on an integrated circuit. A two-phase global serializer master clock generator uses a four-phase internal clock to generate a two-phase global serializer master clock. The two-phase global serializer master clock is distributed globally on the integrated circuit using a distribution path. The integrated circuit has multiple serial communications channels each of which has an associated serializer. Each serializer contains circuitry that derives a number of clock signals from the two phases of the global serializer master clock. Each serializer uses the derived clocks in converting parallel data to serial data for transmission over its associated serial communications channel. The serializers each contain two smaller serializers that convert first and second sets of parallel data to first and second serial outputs. A 2:1 serializer in each serializer merges the first and second serial outputs.

Abstract: Systems and methods are provided using common-mode-voltage bias circuitry to make common-mode-voltage adjustments to differential driver circuitry in integrated circuit differential communications links. Adjustable bias circuitry may be controlled using static and dynamic control signals. Dynamic control signals can be produced by core logic on a programmable logic device or other integrated circuit. Static control signals can be produced by programmable elements. Bias circuit adjustments made at one end of a differential link can be used to improve performance at either end of the link or can be used to improve power consumption or to balance power and performance considerations. The same integrated circuit design can be used in both AC-coupled and DC-coupled environments. The bias circuitry can be formed from an adjustable current source and adjustable resistor. The current source and adjustable resistors can be controlled by the same control signals.

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.