摘要:
A feedback loop circuit includes a phase detector and delay circuits. The phase detector generates an output signal based on a delayed periodic signal. The delay circuits are coupled in a delay chain that delays the delayed periodic signal. Each of the delay circuits includes variable delay blocks and fixed delay blocks that are coupled to form at least two delay paths for an input signal through the delay circuit to generate a delayed output signal. Delays of the variable delay blocks in the delay circuits vary based on the output signal of the phase detector. Each of the delay circuits reroutes the input signal through a different one of the delay paths to generate the delayed output signal based on the output signal of the phase detector during operation of the feedback loop circuit.
摘要:
Circuits, methods, and apparatus for memory interfaces that compensate for skew between a clock signal and DQ/DQS signals that may be caused by a fly-by routing topology. The skew is compensated by clocking the DQ/DQS signals with a phase delayed clock signal, where the phase delay has been calibrated. In one example calibration routine, a clock signal is provided to a receiving device. A DQ/DQS signal is also provided and the timing of their reception compared. A delay of the DQ/DQS signal is changed incrementally until the DQ/DQS signal is aligned with the clock signal at the receiving device. This delay is then used during device operation to delay a signal that clocks registers providing the DQ/DQS signals. Each DQ/DQS group can be aligned to the clock, or the DQS and DQ signals in a group may be independently aligned to the clock at the receiving device.
摘要:
An input buffer circuit has a plurality of selectively enabled differential amplifier circuits, where each differential amplifier is configured for compatibility with a particular differential I/O standard and its corresponding input operating range. For example, the input buffer may have two differential amplifiers suitable for receiving LVDS differential input signals over a wide input operating range, and another differential amplifier suitable for receiving the PCML differential input signals. One or more control signals are provided to the input buffer, e.g., programmably, to selectively enable the required differential amplifier(s) for a given I/O standard.
摘要:
Method and circuitry for implementing high speed multiple-data-rate interface architectures for programmable logic devices. The invention partitions I/O pins and their corresponding registers into independent multiple-data rate I/O modules each having at least one pin dedicated to the strobe signal DQS and others to DQ data signals. The modular architecture facilitates pin migration from one generation of PLDs to the next larger generation.
摘要:
Phase comparators for use in loop circuits (i.e., DLL circuits and PLL circuits) are provided. The phase comparators include a phase detector for comparing a reference clock signal and a feedback signal derived from the loop circuit generated internal clock signal. The phase comparators also include a low-pass noise filter for filtering out erroneously detected phase differences between the reference clock signal and the feedback signal by requiring a certain net number of leading or lagging detections before the compensation circuitry of the loop circuit (i.e., the controlled delay line in a DLL circuit or the controlled oscillator in a PLL circuit) is adjusted. The number of net measurements required before these adjustments take place depends on a programmable bandwidth signal provided to the phase comparator.
摘要:
A programmable I/O element for an I/O terminal of a logic array is suitable for operating according to high speed 110 modes such as double data rate and zero bus turnaround. The I/O element may include an input block with two registers for registering input signals from the terminal upon alternate clock edges. In addition or alternatively, it may include an output block with two registers that separately register output signals from the array on the same clock edge and a multiplexer that alternately outputs those signals. For bidirectional terminals, the multiplexer output is connectable to the I/O terminal via an output buffer, and an output enable block provides an enable signal to a gating input of the output buffer. Programmable delays may be included in the input, output, and output enable paths, in particular to provide a slower turn-on time than turn-off time for the output buffer.
摘要:
Method and circuitry for implementing high speed multiple-data-rate interface architectures for programmable logic devices. The invention partitions I/O pins and their corresponding registers into independent multiple-data rate I/O modules each having at least one pin dedicated to the strobe signal DQS and others to DQ data signals. The modular architecture facilitates pin migration from one generation of PLDs to the next larger generation.
摘要:
Techniques and circuitry are used to more rapidly configuring programmable integrated circuits. Configuration data is input into a programmable integrated circuit in parallel via parallel inputs (705), and this data is also handled internally in parallel. The configuration data will be stored in a data register (722). This data register includes two or more serial register chains, each chain being made up of a serial chain of registers. The configuration data is input into the two of more chains of the data registers in parallel. Circuitry is also provided to handle redundancy.
摘要:
A programmable memory interface circuit includes a programmable DLL delay chain, a phase offset control circuit and a programmable DQS delay chain. The DLL delay chain uses a set of serially connected delay cells, a programmable switch, a phase detector and a digital counter to generate a coarse phase shift control setting. The coarse phase shift control setting is then used to pre-compute a static residual phase shift control setting or generate a dynamic residual phase shift control setting, one of which is chosen by the phase offset control circuit to be added to or subtracted from the coarse phase shift control setting to generate a fine phase shift control setting. The coarse and fine phase shift control settings work in concert to generate a phase-delayed DQS signal that is center-aligned to its associated DQ signals.
摘要:
A circuit includes a locked loop and a phase offset circuit. The locked loop generates first control signals for controlling a first delay in the locked loop. The phase offset circuit delays an input signal by a second delay that is controlled by second control signals to generate a delayed signal. The phase offset circuit generates the second control signals by adjusting the first control signals to increase the accuracy of the delayed signal with respect to a target phase. The second control signals compensate for at least a portion of a change in the second delay that is caused by a variation in at least one of a process, a supply voltage, and a temperature of the circuit.