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: Serial data transmitter circuitry on a PLD includes a number of features that enable the transmitter to support many different communication protocols under a wide range of circuit conditions. Examples of features that the transmitter may include are (1) multiple pre-emphasis circuits of selectable strength and polarity, (2) selectable VOD, (3) selectable slew rate, (4) calibratable termination, (5) selectable common mode voltage, and (6) electrical idle mode.

Abstract: An impedance compensation circuit for inputs of a programmable device includes programmable impedance circuits connected with input nodes. The programmable impedance circuits can be configured to apply a compensating voltages to input nodes to reduce or eliminate unwanted offset voltages. An impedance compensation circuit may include resistors in series or current sources in parallel. A set of bypass switches selectively apply each resistor or current source to an input node, thereby changing the offset voltage of the node and compensating for impedance mismatches. Control logic provides signals to control the bypass switches. The control logic may be implemented using programmable device resources, enabling the control logic to be updated and improved after the manufacturing of the device is complete. The control logic can automatically evaluate offset voltages at any time and change compensating impedances accordingly. This reduces manufacturing costs and takes into account temperature and aging effects.

Abstract: A serial interface for a programmable logic device can be operated according to various communications protocols and includes both a receiver portion and a transmitter portion. The receiver portion includes at least a word or byte alignment stage, a de-skew stage, a rate compensation or matching stage, a padded protocol decoder stage (e.g., 8B/10B decoder circuitry or 64B/66B decoder circuitry), a byte deserializer stage, a byte reorder stage, and a phase compensation stage. The transmitter portion includes at least a phase compensation stage, a byte deserializer stage, and a padded protocol encoder stage (e.g., an 8B/10B encoder circuitry or 64B/66B encoder circuitry). Each stage may have multiple occurrences of relevant circuitry. Selection circuitry, such as multiplexers, selects the appropriate stages, and circuitry within each stage, for the protocol being used.

Abstract: Wide range and dynamically reprogrammable CDR architecture recovers an embedded clock signal from serial input data with a wide range of operating frequencies. In order to support a wide range of data rates, the CDR architecture includes multiple operating parameters. These parameters include various pre/post divider settings, charge pump currents, loop-filter and bandwidth selections, and VCO gears. The parameters may be dynamically reprogrammed without powering down the circuitry or PLD. This allows the CDR circuitry to switch between various standards and protocols on-the-fly.

Abstract: A programmable logic device (PLD) having one or more programmable logic regions and one or more conventional input/output regions additionally has one or more peripheral areas including specialized circuitry. The peripheral specialized regions, which are not connected to the remainder of the programmable logic device (and may be made on separate dies from the remainder of the programmable logic device mounted on a common substrate), and one or both of the programmable logic regions and the conventional I/O regions, have contacts for metallization traces or other interconnections to connect the peripheral specialized regions to the remainder of the programmable logic device. The same PLD can be sold with or without the specialized circuitry capability by providing or not providing the interconnections. The peripheral specialized regions may include high-speed I/O (basic, up to about 3 Gbps, and enhanced, up to about 10-12 Gbps), as well as other types of specialized circuitry.

Abstract: Variable capacitance circuitry includes a fine tuning bank and a medium tuning bank. The fine tuning bank includes a plurality of varactors of progressively increasing size (e.g., width). Only one of these varactors is turned on at any one time. The medium tuning bank includes a plurality of similarly sized varactor circuits. These are turned on selectively in thermometer fashion (e.g., more are turned on (or off) as more (or less) overall capacitance is needed). The medium tuning bank increment is matched to the fine tuning bank range, so that when the fine tuning bank reaches an end of its range, another medium increment can be added or subtracted while the fine tuning bank is reset to the other end of its range. A uniform progression of small, incremental, capacitance changes is therefore provided over the relatively wide tuning range of the medium bank.

Abstract: An all-digital serializer-de-serializer includes an all-digital clock multiplier unit (CMU) circuit, an all-digital clock and data recovery (CDR) circuit, a multiplexer (MUX), and a demultiplexer (DeMUX). The all-digital clock and data recovery (CDR) circuit couples to the all-digital clock multiplier unit (CMU) circuit. The multiplexer (MUX), couples to all-digital clock multiplier unit (CMU) circuit, and serializes data. The demultiplexer (DeMUX), couples to the all-digital clock and data recovery (CDR) circuit, and de-serializes data.

Abstract: Eight-bit ten-bit (8B10B) coding is provided in a hard intellectual property (IP) block with the capability of supporting a greater range of data rates (e.g., data rates less than, equal to, and greater than 3.125 Gbps). Each channel of high speed serial interface circuitry includes receiver circuitry having two 8B10B decoders and transmitter circuitry having two 8B10B encoders. The receiver and transmitter circuitry can be configured to operate in one of three modes of operation: cascade mode, dual channel mode, and single channel mode.

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: Programmable logic device integrated circuitry having differential I/O circuitry is provided. The differential I/O circuitry may include output drivers for providing differential digital output data signals across pairs of output lines. A user may program the I/O circuitry to accommodate different high-speed differential I/O signaling standards. The user may also program the I/O circuitry to provide a desired amount of preemphasis to the output data signals.

Abstract: Data transmitter circuitry on a programmable logic device (“PLD”) includes a plurality of channels of serializer circuitry, and a plurality of clock multiplier units (“CMUs”), each of which is associated with a respective subplurality of the serializer channels. Each CMU includes multiple reference clock signal sources, multiple phase-locked loop (“PLL”) circuits, and circuitry for allowing any PLL to get its reference input from any of the reference sources. Raw and centrally processed clock signals produced by each CMU are distributed to the serializer channels associated with that CMU and, at least in the case of the centrally processed signals, to the serializer channels associated with another CMU. The signal that controls release of parallel data to each serializer channel can be an output signal of that channel, or it can be an output signal of any CMU from which that channel can get a clock signal.

Abstract: Circuitry and methods are provided for an LVDS-like transmitter that may be able to DC couple to a receiver having a CML termination scheme. Replacing the common mode voltage source of an LVDS transmitter with a resistive pulldown to ground may allow the transmitter to interface in a DC coupled fashion with a CML receiver. Further, the resistive pulldown may be programmable. This LVDS-like transmitter may be able to support a wider customer base by allowing it to DC couple to a wider range of termination voltage levels, such as CML termination voltage levels.

Abstract: Eight-bit ten-bit (8B10B) coding is provided in a hard intellectual property (IP) block with the capability of supporting a greater range of data rates (e.g., data rates less than, equal to, and greater than 3.125 Gbps). Each channel of high speed serial interface circuitry includes receiver circuitry having two 8B10B decoders and transmitter circuitry having two 8B10B encoders. The receiver and transmitter circuitry can be configured to operate in one of three modes of operation: cascade mode, dual channel mode, and single channel mode.

Abstract: A delay cell has selectable numbers of parallel load resistance transistors operable in parallel, and a similarly selectable number of bias current transistors connectable in parallel. The delay cell is preferably differential in construction and operation. A voltage controlled oscillator (“VCO”) includes a plurality of such delay cells connected in a closed loop series. Phase locked loop (“PLL”) circuitry includes such a VCO controlled by phase/frequency detector circuitry. The PLL can have a very wide range of operating frequencies as a result of the ability to control the number of load resistance transistors and bias current transistors that are active or inactive in each delay cell. Such activation/deactivation may be programmable or otherwise controlled.

Abstract: Programmable logic device integrated circuitry having I/O circuitry portions having different maximum speed capabilities and different amounts of programmability for supporting various I/O signaling standards is provided. High-speed I/O circuitry and low-speed I/O circuitry may be provided. The high-speed I/O circuitry may have differential I/O drivers and may not be programmable. Relatively few I/O lines may be connected to the high-speed I/O circuitry. The low-speed I/O circuitry may be programmable so that a user may configure the low-speed I/O circuitry to support different I/O signaling standards. Intermediate-speed I/O circuitry may be provided that is more flexible than the high-speed circuitry and operates at higher maximum I/O data rates than the low-speed I/O circuitry.

Abstract: Programmable logic device integrated circuitry having differential I/O circuitry is provided. The differential I/O circuitry may include output drivers for providing differential digital output data signals across pairs of output lines. A user may program the I/O circuitry to accommodate different high-speed differential I/O signaling standards. The user may also program the I/O circuitry to provide a desired amount of preemphasis to the output data signals.

Abstract: Programmable logic device integrated circuitry having differential I/O circuitry is provided. The differential I/O circuitry may include output drivers for providing differential digital output data signals across pairs of output lines. A user may program the I/O circuitry to accommodate different high-speed differential I/O signaling standards. The user may also program the I/O circuitry to provide a desired amount of preemphasis to the output data signals.

Abstract: A programmable logic device architecture. This programmable logic architecture includes a first logic block (425) containing programmable logic elements for performing logic functions. The architecture may also include a diagnostic block interface (415), which interfaces with the first logic block (425), for performing JTAG functions, configuring the first logic block (425), initializing the first logic block (425), interfacing with off-chip diagnostic and test devices and equipment, and performing other similar functions. The first logic block (425) may be programmably coupled to other components on the integrated circuit using a first programmable interconnect network (511). The first logic block (425) includes a plurality of second logic blocks (505) which may be programmably coupled using a second programmable interconnect network (521). The second programmable interconnect network (521) may be programmably coupled to the first programmable interconnect network (511).

Abstract: A programmable logic device (PLD) that provides the capability to observe and control the logic state of buried internal nodes is disclosed. The PLD provides shadow storage units for internal nodes such as logic element registers, memory cells, and I/O registers. A sample/load data path includes bidirectional data buses and shift register that facilitate the sampling of internal nodes for observing their logic states, and loading of internal nodes for controlling their logic states.