Abstract: In one embodiment, a configurable delay element has three stages. The first stage has an 8-buffer first delay chain and an (8×1) first mux that selects one of the eight first-delay-chain outputs. The second stage has a 24-buffer second delay chain connected to receive the first-mux output and organized into three 8-buffer sub-chains and a (4×1) second mux that selects one of the four second-delay-chain outputs. The third stage has a 96-buffer third delay chain connected to receive the second-mux output and organized into three 32-buffer sub-chains and a (4×1) third mux that selects one of the four third-delay-chain outputs as the delay-element output signal. A delay-element controller provides glitch-less updates to the signal used to control the delay-element muxes by timing those updates to occur when all delay-element buffers have the same state. The controller bases the update timing on the delay-element output signal.

Abstract: In certain embodiments of the invention, a serializer has (a) an initial, transfer stage that transfers incoming parallel data from a relatively slow timing domain to a relatively fast timing domain and (b) a final, serializing stage that converts the parallel data into serialized data. Between the transfer stage and the serializing stage is an update stage that (i) buffers data between the initial and final stages and (ii) can be used to toggle the serializer between an N?1 operating mode (that serializes (N?1) bits of parallel data) and an N+1 operating mode (that serializes (N+1) bits of parallel data) to achieve a net N:1 gearing ratio where N is an odd integer. The serializer can be configurable to support other gearing ratios as well.

Abstract: In one embodiment, a configurable delay element has three stages. The first stage has an 8-buffer first delay chain and an (8×1) first mux that selects one of the eight first-delay-chain outputs. The second stage has a 24-buffer second delay chain connected to receive the first-mux output and organized into three 8-buffer sub-chains and a (4×1) second mux that selects one of the four second-delay-chain outputs. The third stage has a 96-buffer third delay chain connected to receive the second-mux output and organized into three 32-buffer sub-chains and a (4×1) third mux that selects one of the four third-delay-chain outputs as the delay-element output signal. A delay-element controller provides glitch-less updates to the signal used to control the delay-element muxes by timing those updates to occur when all delay-element buffers have the same state. The controller bases the update timing on the delay-element output signal.

Abstract: A flexible delay cell architecture and related methods are provided that may be used, for example, with input/output (I/O) blocks of a programmable logic device (PLD). In one implementation, a PLD includes a delay cell comprising a plurality of delay elements. The delay elements are adapted to delay an input signal to provide an output signal according to a delay setting corresponding to a number of the delay elements. The PLD also includes a register adapted to store the delay setting. The PLD further includes an edge monitor adapted to signal whether an edge transition of the output signal has occurred during a time window. In addition, the PLD includes logic adapted to adjust the delay setting stored by the register in response to the edge monitor signaling the edge transition.

Abstract: In one embodiment, an integrated circuit such as an FPGA includes one or more data I/O blocks, one or more FIFOs, and a FIFO controller. At least one data I/O block receives an incoming bit stream from an external device. At least one FIFO is connected to receive a corresponding incoming bit stream from a corresponding data I/O block. The FIFO controller controls operations of the one or more FIFOs, such that (i) bits from the corresponding data I/O block are written into the at least one FIFO using a FIFO write clock that is based on an incoming clock signal and (ii) bits are read out from the at least one FIFO using a FIFO read clock that is based on a local reference clock signal.

Abstract: Systems and methods are disclosed herein to provide improved jitter tolerant delay-locked loop circuitry. For example, in accordance with an embodiment of the present invention, an integrated circuit includes a plurality of delay cells each having a plurality of programmable delay taps. Each delay cell is adapted to provide a delayed clock signal delayed by a selected number of the delay taps. A phase detector is adapted to compare a first clock signal with a selected one of the delayed clock signals to obtain a comparison result and provide a plurality of control signals in response to the comparison result. An arithmetic logic unit (ALU) is adapted to vary the selected number of delay taps in response to the control signals provided by the phase detector.

Abstract: In one embodiment of the invention, an integrated circuit, such as an FPGA, comprises a distributed FIFO architecture that supports data transfer from an external device, such as an SDRAM, via an interface that receives a non-continuous, asynchronous strobe clock and a data lane having a plurality of bit lines from the external device. The distributed FIFO architecture comprise a FIFO for each bit line and a FIFO controller. Under control of the FIFO controller, data is written into each FIFO using a FIFO write clock based on the strobe clock, while data is read out from each FIFO using a FIFO read clock based on a local reference clock of the integrated circuit. The distributed FIFO architecture is designed to handle a range of possible phase differences between the FIFO write and read clocks to safely convert from the asynchronous, non-continuous strobe domain to a local continuous clock domain.

Abstract: When certain digital circuit devices receive data bus signals, I/O interfaces need to sample the data signals during a time when these signals are both valid and stable. Typically, the data signals are sampled at a time corresponding to a point halfway between rising and falling edges of a reference clock signal associated with the data bus, which sampling time corresponds to a 90-degree phase shift of the reference clock signal. In one embodiment of the invention, a delay count generator determines a delay value corresponding to a quarter cycle (i.e., 90 degrees) of the reference clock signal. In making this determination, a counter counts the number of clock cycles of an internally generated, relatively high-frequency clock signal, where the number corresponds to a specified portion (e.g., one half) of a period of a divided-down version of the reference clock signal. That number can then be used to generate the 90-degree delay value.

Abstract: Systems and methods are disclosed herein to provide improved jitter tolerant delay-locked loop circuitry. For example, in accordance with an embodiment of the present invention, an integrated circuit includes a plurality of delay cells each having a plurality of programmable delay taps. Each delay cell is adapted to provide a delayed clock signal delayed by a selected number of the delay taps. A phase detector is adapted to compare a first clock signal with a selected one of the delayed clock signals to obtain a comparison result and provide a plurality of control signals in response to the comparison result. An arithmetic logic unit (ALU) is adapted to vary the selected number of delay taps in response to the control signals provided by the phase detector.

Abstract: When certain digital circuit devices receive data bus signals, I/O interfaces need to sample the data signals during a time when these signals are both valid and stable. Typically, the data signals are sampled at a time corresponding to a point halfway between rising and falling edges of a reference clock signal associated with the data bus, which sampling time corresponds to a 90-degree phase shift of the reference clock signal. In one embodiment of the invention, a delay count generator determines a delay value corresponding to a quarter cycle (i.e., 90 degrees) of the reference clock signal. In making this determination, a counter counts the number of clock cycles of an internally generated, relatively high-frequency clock signal, where the number corresponds to a specified portion (e.g., one half) of a period of a divided-down version of the reference clock signal. That number can then be used to generate the 90-degree delay value.

Abstract: Systems and methods are disclosed to provide clock and data synchronization for input/output interfaces of a programmable logic device. In accordance with one embodiment, a phase-locked loop or a delay-locked loop is employed to synchronize signals for input/output circuitry. In accordance with another embodiment, a clock divider along with an edge clock distribution scheme is employed to distribute clock and reset signals for input/output circuitry.

Abstract: Systems and methods are disclosed to provide clock and data synchronization for input/output interfaces of a programmable logic device. In accordance with one embodiment, a phase-locked loop or a delay-locked loop is employed to synchronize signals for input/output circuitry. In accordance with another embodiment, a clock divider along with an edge clock distribution scheme is employed to distribute clock and reset signals for input/output circuitry.

Abstract: Clock generation techniques are disclosed to provide clock generation with duty cycle replication. The clock generation techniques may further compensate for clock insertion delays and minimize distortion due to clock distribution networks.

Abstract: Systems and methods are disclosed herein to implement signal delay in integrated circuits. For example, in accordance with an embodiment of the present invention, a master delay circuit may digitally control one or more slave delay cells to support various applications of a programmable logic device.

Abstract: A programmable logic device (PLD), such as a field programmable gate array (FPGA) has a logic core surrounded on one or more sides by an input/output (I/O) interface having one or more programmable I/O buffers (PIBs). At least one PIB can be programmed to perform two or more of (a) a pass-through data input mode, (b) an input register mode; (c) a double data rate (DDR) input mode, (d) one or more demux input modes, (e) one or more DDR demux input modes. In addition or alternatively, at least one PIB can be programmed to perform two or more of (a) a pass-through data output mode, (b) an output register mode, (c) a DDR output mode, (d) one or more mux output modes, and (e) one or more DDR mux output modes. As such, devices of the present invention are flexible enough to support both low-rate and high-rate interface applications, while efficiently using device resources.

Abstract: A programmable logic device (PLD) with a programmable logic core, block memory, and I/O circuitry has one or more blocks of standard-cell logic (SLBs) that are integrated into the PLD design to enable each SLB to be programmably connected to any one or more of the programmable core, the block memory, and/or the I/O circuitry. The addition of standard-cell-based functional blocks creates a PLD with increased overall logic density, a net smaller die size per function, lowered cost, and improvements to both power and performance characteristics relative to equivalent conventional PLDs, such as FPGAs.

Abstract: A programmable logic device (PLD), such as a field programmable gate array (FPGA) has a logic core surrounded on one or more sides by an input/output (I/O) interface having one or more programmable I/O buffers (PIBs). At least one PIB can be programmed to perform two or more of (a) a pass-through data input mode, (b) an input register mode; (c) a double data rate (DDR) input mode, (d) one or more demux input modes, (e) one or more DDR demux input modes. In addition or alternatively, at least one PIB can be programmed to perform two or more of (a) a pass-through data output mode, (b) an output register mode, (c) a DDR output mode, (d) one or more mux output modes, and (e) one or more DDR mux output modes. As such, devices of the present invention are flexible enough to support both low-rate and high-rate interface applications, while efficiently using device resources.

Abstract: Systems and methods are disclosed herein to provide access to memory cells within a programmable logic device. For example, in accordance with an embodiment of the present invention, a serial memory interface is associated with each special functional block within a programmable logic device to provide access to configuration memory cells of the special functional block.

Abstract: A programmable logic device (PLD) with a programmable logic core, block memory, and I/O circuitry has one or more blocks of standard-cell logic (SLBs) that are integrated into the PLD design to enable each SLB to be programmably connected to any one or more of the programmable core, the block memory, and/or the I/O circuitry. The addition of standard-cell-based functional blocks creates a PLD with increased overall logic density, a net smaller die size per function, lowered cost, and improvements to both power and performance characteristics relative to equivalent conventional PLDs, such as FPGAs.

Abstract: Systems and methods are disclosed to provide clock and data synchronization for input/output interfaces of a programmable logic device. In accordance with one embodiment, a phase-locked loop or a delay-locked loop is employed to synchronize signals for input/output circuitry. In accordance with another embodiment, a clock divider along with an edge clock distribution scheme is employed to distribute clock and reset signals for input/output circuitry.