Abstract: A programmable logic device includes configurable phase-locked loop (PLL) circuitry that outputs multiple clock signals having programmable phases and frequencies. Each output signal is programmably selectable for use as an external clock, internal global clock, internal local clock, or combinations thereof. The PLL circuitry has programmable frequency dividing, including programmable cascaded frequency dividing, and programmable output signal multiplexing that provide a high degree of clock design flexibility.

Abstract: A programmable logic integrated circuit device (“PLD”) includes programmable logic and a dedicated (i.e., at least partly hard-wired) digital signal processing region for performing or at least helping to perform digital signal processing tasks that are unduly inefficient to implement in the more general-purpose programmable logic and/or that, if implemented in the programmable logic, would operate unacceptably or at least undesirably slowly. The digital signal processing region may include multiple digital signal processing stages. The digital signal processing region may include a multiplier stage and one ore more stages that can operate in combination with the multiplier stage. The digital signal processing region has a plurality of modes such as for providing multiply-and-accumulate operation, multiply-and-add operation, etc.

Abstract: A phase-locked loop (“PLL”) for use in a programmable logic device (“PLD”) is constructed with modular components, which may be digital, and which may be programmable or adjustable, in place of the conventional analog charge pump and loop filter. Connections are provided between those components and the remainder of the PLD so that if the PLL is not being used in a particular user design of the PLD, the PLL modular components may be used by other portions of the PLD. Similarly, those connections allow other portions of the PLD to be used in place of one or more of the modular components where more complex or special filtering than can be provided by the modular components is required.

Abstract: In a programmable logic device having high-speed serial interface channels, a clock distribution network for providing one or more high-speed clocks to dynamic phase alignment circuitry of those high-speed serial interfaces includes at least one bus that is segmentable (e.g. using tristatable buffers). This allows the bus to be divided into different portions that can be connected to different clock sources when the high-speed serial interfaces are running at different speeds. In one embodiment, the segmenting elements (e.g., the aforementioned buffers) are located between selected channels (e.g., every fourth channel), limiting the size of the different segments. In another embodiment, segmenting elements are located between each channel, allowing complete user freedom in selecting the sizes of the segments. Thus, instead of providing a bus for every clock source, multiple clocks can be made available to different channels by segmenting a single bus.

Abstract: A phase-locked loop (“PLL”) for use in a programmable logic device (“PLD”) is constructed with modular components, which may be digital, and which may be programmable or adjustable, in place of the conventional analog charge pump and loop filter. Connections are provided between those components and the remainder of the PLD so that if the PLL is not being used in a particular user design of the PLD, the PLL modular components may be used by other portions of the PLD. Similarly, those connections allow other portions of the PLD to be used in place of one or more of the modular components where more complex or special filtering than can be provided by the modular components is required.

Abstract: In a programmable logic device having dedicated multiplier circuitry, some of the scan chain registers normally used for testing the device are located adjacent input registers of the multipliers. Those scan chain registers are ANDed with the input registers, and can be loaded with templates of ones and zeroes. This allows, e.g., subset multiplication if the least significant bits are loaded with zeroes and the remaining bits are loaded with ones. The multipliers preferably are arranged in blocks with other components, such as adders, that allow them to be configured as finite impulse response (FIR) filters. In such configurations, the scan chain registers can be used to load filter coefficients, avoiding the use of scarce logic and routing resources of the device.

Abstract: A loop circuit (PLL or DLL) uses a dual-gain voltage-controlled component (VCO or VCDL) to achieve a phase (and frequency) lock with reduced jitter. A coarse control feedback path includes a detector for achieving an approximate lock. This path operates over a wide range and therefore feeds a VCO or VCDL input with relatively high gain. However, input on that path is fixed once coarse frequency lock is achieved, so it does not contribute to jitter. A fine control path includes a detector whose output fine tunes the lock. Although this path is susceptible to noise, its operating range is relatively small, so its VCO or VCDL input has relatively low gain. Therefore jitter from magnification of noise by that gain is relatively small. The loop circuit can be used in a programmable logic device, in which case various loop parameters may be determined by programmable values.

Abstract: Dynamic phase alignment circuitry selects from among several, phase-distributed, candidate clock signals the one of those signals that is currently best for use in controlling the timing of sampling of a serial data signal to recover the data from that signal. The circuitry selects two phase-adjacent ones of the candidate clock signals that are currently the two best candidates for final selection. The circuitry makes a final selection of the generally better one of these two best candidates in a way that avoids unproductive switching back and forth between these two best candidates.

Abstract: A bypassable latch circuit consumes less power in the bypass mode than it does in the latched mode. The circuit includes a flip-flop whose output is routed to an input of a multiplexer. The other input of the multiplexer is the input of the flip-flop as well. The multiplexer is used to select as the latch output either the registered or latched flip-flop output, or the flip-flop input. The flip-flop is modified by replacing the inverter at the flip-flop clock input with a logic gate that accepts as inputs both the clock input and a control input. The control input can cause the flip-flop to ignore the clock, preventing switching that consumes power by charging and discharging capacitive elements in the flip-flop.

Abstract: A phase-locked loop (“PLL”) for use in a programmable logic device (“PLD”) is constructed with modular components, which may be digital, and which may be programmable or adjustable, in place of the conventional analog charge pump and loop filter. Connections are provided between those components and the remainder of the PLD so that if the PLL is not being used in a particular user design of the PLD, the PLL modular components may be used by other portions of the PLD. Similarly, those connections allow other portions of the PLD to be used in place of one or more of the modular components where more complex or special filtering than can be provided by the modular components is required.

Abstract: A programmable logic device includes configurable phase-locked loop (PLL) circuitry that outputs multiple clock signals having programmable phases and frequencies. Each output signal is programmably selectable for use as an external clock, internal global clock, internal local clock, or combinations thereof. The PLL circuitry has programmable frequency dividing, including programmable cascaded frequency dividing, and programmable output signal multiplexing that provide a high degree of clock design flexibility.

Abstract: In a specialized functional region of a programmable logic device, in which certain components may not be used, those components can be placed in a low-power mode so that they do not switch. For example, in an adder which is not being used but is receiving inputs, the current path for the adding circuitry is interrupted, while the output is forced low. If the adder is a carry/look-ahead adder, the GENERATE and PROPAGATE signals normally used in subsequent stages to predict the value of the carry signal are forced to constant values even if the inputs to the adder are changing.

Abstract: A programmable logic device is provided that includes a MAC block having mode splitting capabilities. Different modes of operation may be implemented simultaneously whereby the multipliers and other DSP circuitry of the MAC block may be allocated among the different modes of operation. For example, one multiplier may be used to implement a multiply mode while another two multipliers may be used to implement a sum of two multipliers mode.

Abstract: A phase-locked loop (“PLL”) for use in a programmable logic device (“PLD”) is constructed with modular components, which may be digital, and which may be programmable or adjustable, in place of the conventional analog charge pump and loop filter. Connections are provided between those components and the remainder of the PLD so that if the PLL is not being used in a particular user design of the PLD, the PLL modular components may be used by other portions of the PLD. Similarly, those connections allow other portions of the PLD to be used in place of one or more of the modular components where more complex or special filtering than can be provided by the modular components is required.

Abstract: A phase-locked loop (“PLL”) for use in a programmable logic device (“PLD”) is constructed with modular components, which may be digital, and which may be programmable or adjustable, in place of the conventional analog charge pump and loop filter. Connections are provided between those components and the remainder of the PLD so that if the PLL is not being used in a particular user design of the PLD, the PLL modular components may be used by other portions of the PLD. Similarly, those connections allow other portions of the PLD to be used in place of one or more of the modular components where more complex or special filtering than can be provided by the modular components is required.

Abstract: A loop circuit (PLL or DLL) uses a dual-gain voltage-controlled component (VCO or VCDL) to achieve a phase (and frequency) lock with reduced jitter. A coarse control feedback path includes a detector for achieving an approximate lock. This path operates over a wide range and therefore feeds a VCO or VCDL input with relatively high gain. However, input on that path is fixed once coarse frequency lock is achieved, so it does not contribute to jitter. A fine control path includes a detector whose output fine tunes the lock. Although this path is susceptible to noise, its operating range is relatively small, so its VCO or VCDL input has relatively low gain. Therefore jitter from magnification of noise by that gain is relatively small. The loop circuit can be used in a programmable logic device, in which case various loop parameters may be determined by programmable values.

Abstract: In a programmable logic device having dedicated multiplier circuitry, some of the scan chain registers normally used for testing the device are located adjacent input registers of the multipliers. Those scan chain registers are ANDed with the input registers, and can be loaded with templates of ones and zeroes. This allows, e.g., subset multiplication if the least significant bits are loaded with zeroes and the remaining bits are loaded with ones. The multipliers preferably are arranged in blocks with other components, such as adders, that allow them to be configured as finite impulse response (FIR) filters. In such configurations, the scan chain registers can be used to load filter coefficients, avoiding the use of scarce logic and routing resources of the device.

Abstract: A PLL circuit is described. The PLL circuit includes: a signal generator; and a spread spectrum modulator coupled to the signal generator, where the spread spectrum modulator receives a control voltage as an input and provides a spread spectrum control voltage to the signal generator in response to the control voltage. In one embodiment, the spread spectrum modulator includes at least one selector, where the at least one selector selects a plurality of voltage levels that correspond to a spread mode and percentage of spread for the spread spectrum modulator.

Abstract: A testing circuit and method for a phase-locked loop allow measurement of leakage currents in the phase-locked loop components. By forcing the output of the phase-frequency detector to a particular state, the charge pump can be disabled. This disables the effect of feedback in the phase-locked loop, and allowing the output frequency to be determined by the voltage on the control voltage node at the time the feedback is disabled. If there is no leakage, the control voltage, and therefore the output frequency, should remain the same as they were at the moment feedback was disabled. Monitoring the output frequency for changes provides an indication of the presence or absence of leakage. Conducting the test using two different charge pump reference currents allows one to detect leakage resulting from charge pump mismatch.

Abstract: Method and apparatus for locking a phase lock loop, where the method includes selecting a frequency window corresponding to a VCO output frequency, selecting a control voltage corresponding to the frequency window and providing the control voltage to the control voltage circuit which subsequently uses the selected control voltage as the starting control voltage of the phase lock loop.