Abstract: In one embodiment of the invention, a receiver has two mux circuits, two receiver circuits, and a mixer. The muxes select first and second input signals for the receiver circuits. A p-type transistor in a transmission gate in each mux is connected (i) at its channel nodes between a pad and the mux output and (ii) to receive a control signal at its gate node. Control circuitry for the p-type transistor implements a threshold reduction filter that ensures that a maximum voltage level at the mux output is at least a threshold below the mux's power supply voltage. Based on first and second input signals, the first receiver circuit generates first and second intermediate signals, and the second receiver circuit generates third and fourth intermediate signals. The mixer circuit combines the intermediate signals to generate first and second output signals, wherein the first and second receiver circuits effectively operate over different ranges of common-mode voltages.

Abstract: Systems and methods provide non-volatile memory architectures for programmable logic devices. For example, a programmable logic device may include logic blocks, input/output blocks, and configuration memory to store configuration data for configuration of the logic blocks and the input/output blocks. A first non-volatile memory may store user information, besides configuration data, and a first port includes a dedicated serial peripheral interface to provide access to the first non-volatile memory.

Abstract: In one embodiment of the invention, an integrated circuit, such as an FPGA, has one or more programmable termination schemes, each having a plurality of resistive termination legs connected in parallel, and a calibration circuit designed to control each termination scheme for process, voltage, and temperature (PVT) variations. The sense element in the calibration circuit and each resistive leg in each termination scheme has a transistor-based transmission gate connected in series with a non-silicided poly (NSP) resistor. The negative temperature coefficient of resistivity of each NSP resistor offsets the positive temperature coefficient of resistivity of the corresponding transmission gate to provide a temperature-independent sense element and temperature-independent termination legs.

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: An integrated circuit includes a first bus and at least one array of embedded memories. Each array includes a second bus such as a bidirectional bus coupled to the embedded memories and to the first bus such that test vectors in the form of data words can be written from the first bus to selected embedded memories in the array. Also included is a built-in-self-test (BIST) circuit operable to compare data words on the first bus to data words read back from the selected embedded memories through the bidirectional bus.

Abstract: Systems and methods provide synchronization techniques across a number of communication channels. For example, in accordance with an embodiment of the present invention, a synchronization scheme is disclosed for synchronizing across multiple data transmission channels, with each transmission channel multiplexing parallel data into serial data.

Abstract: In one embodiment, a (negative-voltage) charge pump with one or more stages that receives a (high) input voltage and generates a higher-magnitude (negative) output voltage. Each stage has two capacitors for storing charges and two branches that alternate to transmit a higher-magnitude output voltage at every clock half cycle. Each branch has a PMOS transistor and a NMOS transistor. To reduce the effects of back body from the substrate, two transistors are constructed with three wells and two with four wells, where the number of wells per device is dependent upon the substrate type used.

Abstract: A programmable logic device may comprise a plurality of programmable resources and non-volatile configuration memory to store configuration data by which to configure the programmable resources. Test override circuitry may determine a test mode and selectively override the configuration data stored in the non-volatile configuration memory during the test mode for configuring the programmable resources based at least in part on test configuration data other than the configuration data stored in the non-volatile memory. A buffer may be operable to drive a configuration select node for at least one of the programmable resources for designating a configuration therefore based on the configuration data of the non-volatile memory. The test override circuitry may comprise a pull-down circuit operable, when enabled dependent on the test configuration data, to drive the buffer with a high/low level capable of overriding a state of the non-volatile configuration memory.

Abstract: Systems and methods are disclosed herein to provide reconfiguration techniques for PLDs. For example, in accordance with an embodiment of the present invention, a programmable logic device includes logic blocks, input/output blocks, a volatile memory block, and configuration memory cells to store configuration data for configuration of the logic blocks, the input/output blocks, and the volatile memory block of the programmable logic device. The programmable logic device further includes circuit techniques for preventing loss of data stored in the volatile memory block due to a reconfiguration. Furthermore, for example, the programmable logic device may further prevent the loss of data stored in user registers or loss of input/output personality due to the reconfiguration.

Abstract: A programmable logic device includes a plurality of input/output blocks providing an input/output interface for the programmable logic device and a first and second plurality of logic blocks providing programmable logic functions, with only the second plurality of logic blocks further adapted to provide distributed random access memory functions. A routing structure programmably interconnects the input/output blocks and the first and second plurality of logic blocks. Configuration memory cells store configuration data to configure the input/output blocks, the first and second plurality of logic blocks, and the routing structure. In one embodiment, there are at least twice as many logic blocks in the first plurality of logic blocks than in the second plurality of logic blocks. In another embodiment, the first and second plurality of logic blocks are arranged in one or more rows, and the programmable logic device includes one or more rows of embedded block RAM.

Abstract: Systems and methods are disclosed herein to provide improved clock, delay, and skew techniques. For example, in accordance with an embodiment of the present invention, an integrated circuit includes a clock generator to provide a bias signal and a clock signal, with control logic providing a delay control signal based on the bias signal and the control signal. A delay circuit provides a delay to the clock signal based on the delay control signal.

Abstract: In accordance with an embodiment of the present invention, a comparator system includes a plurality of multiplexers adapted to multiplex a number of differential input signals and a number of differential reference signals. A differencing circuit receives a differential input signal and a differential reference signal from the multiplexers and provides a differential output signal, which is used to provide a differential comparator output signal. A latch may be provided to perform differential-to-single ended conversion on the differential comparator output signal to provide a latch output signal. An output circuit may provide a registered digital output signal based on the latch output signal.

Abstract: Various approaches are disclosed to provide improved compression and decompression of configuration data for use with programmable logic devices (PLDs). Uncompressed configuration data may comprise a plurality of rows. In accordance with one embodiment, a method of converting the uncompressed configuration data into compressed configuration data includes encoding a row of configuration data comprising only bulk erase bytes into a first bit pattern within a fixed length header. The method also includes encoding a number of continuous bulk erase bytes of configuration data in a row that includes more than bulk erase bytes into a second bit pattern within the fixed length header. The method further includes encoding at least a portion of a row of configuration data according to a Lempel-Ziv (LZ) compression process into a third bit pattern within the fixed length header.

Abstract: An improved output buffer having a digital output slew control and compensation for manufacturing process variations. Output slewing is accomplished by sequencing digital drive signals to paralleled output transistors. In one embodiment, a pre-driver sequences the drive signals by using the propagation delays of serially coupled digital logic gates to reduce power supply droop and/or ground bounce. The output transistors are turned off substantially simultaneously to avoid undesirable power supply DC current flow when the output buffer changes state. Programmably configuring the number of paralleled transistors that may be turned on at any given time allows a user to compensate for manufacturing process variations and determine the output impedance/drive capacity of the buffer.

Abstract: Improved common mode feedback techniques are provided for charge pumps, phase-locked loops (PLLs), and other circuits. For example, in accordance with an embodiment of the present invention, a circuit includes a loop filter having first and second loop filter nodes. An amplifier is provided having first and second differential inputs respectively coupled to the first and second loop filter nodes. A first current source is coupled to the first loop filter node and a second current source is coupled to the second loop filter node. The first and second current sources continuously adjust a common mode voltage of the loop filter nodes.

Abstract: A logic circuit is disclosed that is tolerant of logic signals with voltages different from the voltage of the logic circuit power supply. In one embodiment, the logic circuit has an inverting amplifier therein, the amplifier having at least one input and an output and is powered by the power supply. A first transistor, in responsive to the output of the amplifier, biases the input of the amplifier to assure substantially no static current flows through the amplifier when a logic-low is present on the amplifier output. A second transistor couples at least one logic input of the logic circuit to the input of the amplifier. In one embodiment, the second transistor impedes static current flow from the first transistor, through the second transistor, to the logic input. Various other embodiments of the logic circuit include a latch/flip-flop, multiplexer, and a complex logic gate.

Abstract: A method of calculating a diagonal interleaved parity word for groups of words sampled from a bus is provided, wherein a predetermined number of words are included in each sampling cycle. The bus carries successive data words that are followed by a control word. At each sampling cycle, diagonal XOR calculations chains are propagated through the words that were sampled. However, if a sampling cycle includes the control word, the words following the control word are assigned to logical zero values. The diagonal XOR calculation chains may then be terminated after processing the words in this sampling cycle to derive an intermediate diagonal parity word. The intermediate diagonal parity word may then be adjusted according to the number of words that were assigned logical zero values to calculate a second diagonal interleaved parity word.

Abstract: A programmable logic device in accordance with an embodiment of the invention includes configurable logic blocks, embedded random access memory (RAM) blocks, and input/output blocks adapted to transfer information into or out of the programmable logic device. An interconnect architecture is adapted to route information among the configurable logic blocks, embedded RAM blocks, and input/output blocks within the programmable logic device. An interface block is provided that couples an embedded RAM block and an input/output block but not a logic block to the interconnect architecture.

Abstract: A multiport memory in one embodiment of the invention includes a memory cell array, where each column in the array has two exterior complementary bitline pairs and zero, one, or more interior complementary bitline pairs. Across each pair of adjacent columns in the array, the adjacent exterior bitline pairs are associated with the same port in the multiport memory. In addition, within each column, the two exterior bitline pairs have the same, non-zero number of crossovers, and, across each pair of adjacent columns, the exterior bitline pairs have different numbers of crossovers. Furthermore, each column has at least one reference signal line located between the two exterior bitline pairs.

Abstract: Systems and methods are disclosed herein to provide improved I/O techniques. For example, in accordance with an embodiment of the present invention, an integrated circuit includes a reference circuit adapted to receive a first reference signal and provide a second plurality of reference signals based on the first reference signal, with the reference circuit providing default voltage levels for the second plurality of reference signals if a first control signal is asserted. An input/output circuit, coupled to the reference circuit and to an output driver, receives the second plurality of reference signals to control the output driver to provide an output signal, with the output driver operated with the default voltage levels if the first control signal is asserted.