Abstract: In this paper, we provide a comprehensive study of the mappability of a via-configurable gate array (VCGA). Although, the base cell of the VCGA is simple, by customizing only via masks it can implement various combinational logic functions, sequential elements, and SRAM cells. Our VCGA can be efficiently configured into SRAM arrays, adders and multipliers. The strong configurability of our VCGA allows us to minimize the number of fixed parts in a general-purpose VCGA fabric, which greatly improves area utilization.

Abstract: We present the design of a high-performance, highly pipelined asynchronous FPGA. We describe a very fine-grain pipelined logic block and routing interconnect architecture, and show how asynchronous logic can efficiently take advantage of this large amount of pipelining. Our FPGA, which does not use a clock to sequence computations, automatically self-pipelines" its logic without the designer needing to be explicitly aware of all pipelining details. This property makes our FPGA ideal for throughput-intensive applications and we require minimal place and route support to achieve good performance. Benchmark circuits taken from both the asynchronous and clocked design communities yield throughputs in the neighborhood of 300--400 MHz in a TSMC 0.25m process and 500--700 MHz in a TSMC 0.18m process.

Abstract: System-on-chip (SoC) designs integrate a variety of cores and I/O interfaces, which usually operate at different clock frequencies. Communication between unlocked clock domains requires careful synchronization, which inevitably introduces metastability and some uncertainty in timing. Thus, any chip with multiple clock domains is already globally asynchronous. We have devised a more elegant and efficient solution to the multiple-clock-domain problem. Instead of gluing synchronous domains directly to each other with clock-domain bridges, we use asynchronous-circuit design techniques to handle all clock-domain crossing as well as all cross-chip communication and routing. The phase-locked loop (PLL) and clock distribution can be entirely local to each synchronous core, easing timing closure and improving the reusability of cores across multiple designs. Our solution, Nexus, is a globally asynchronous, locally synchronous (GALS) interconnect that features a 16-port, 36-bit asynchronous crossbar. The crossbar connects through asynchronous channels to clock-domain converters for each synchronous module. To ensure that Nexus will work robustly in a commercial application, we developed and applied many verification and test strategies, including novel variations of noise analysis, timing analysis, and fault and delay testing.

Abstract: Multi-V/sub DD/ design is an effective way to reduce power consumption, but the need for level conversion imposes delay and energy penalties that limit the potential gains. In this paper, we describe new level converting circuits that provide 10%-61% lower energy consumption at equivalent or better speeds compared to those available in the literature. Furthermore, we make the argument that level converters should be evaluated largely by their maximum speed since slower level converters consume valuable timing slack that can be used to reduce the energy of other gates in the circuit. Based on this criterion, we find the new structures to offer up to a 25% speed improvement over conventional level converters. Using an efficient dual V/sub DD/ voltage assignment algorithm, we show that this speed improvement can yield a reduction of up to 7.3% in total circuit power in small benchmark circuits. We also propose embedding the functionality of logic gates into the level converting circuits. For typical values of the second supply voltage, this technique can reduce delay by 15% at constant energy or lower energy by up to 30% at fixed delay.

Abstract: High-performance, highly pipelined asynchronous FPGAs employ a very fine-grain pipelined logic block and routing interconnect architecture. These FPGAs, which do not use a clock to sequence computations, automatically “self-pipeline” their logic without the designer needing to be explicitly aware of all pipelining details. The FPGAs include arrays of logic blocks or cells that include function units, conditional units and other elements, each of which is constructed using basic asynchronous pipeline stages, such as a weak condition half buffer and a precharge half buffer.

Abstract: A resonant global clock-distribution network operating at 4.6GHz is designed in a 90nm 1.0V CMOS technology. Unique to this approach is the set of on-chip spiral inductors that resonate with the clock capacitance, resulting in 20% recycling of global clock power.

Abstract: A reconfigurable circuit of reduced circuit scale. The reconfigurable circuit of the present invention comprises a plurality of ALUs capable of changing functions. The plurality of ALUs are arranged in a matrix. At least one connection unit capable of establishing connection between the ALUs selectively is provided between the stages of the ALUs. This connection unit is not intended to allow connection between all the logic circuits in adjoining stages, but is configured so that the logic circuits are each connectable with only some of the logic circuits pertaining to the other stages. The connection limitation allows a reduction in circuit scale.

Abstract: A new form of logic diagnosis is described that is suitable for diagnosing fails in combinational logic. It can diagnose defects that can affect arbitrarily many elements in the integrated circuit. It operates by first identifying patterns during which only one element is affected by the defect, and then diagnosing the fails observed during the application of such patterns, one pattern at a time. Single stuck-at faults are used for this purpose, and the aggregate of stuck-at fault locations thus identified is then further analyzed to obtain the most accurate estimate of the identities of those elements that can be affected by the defect. This approach to logic diagnosis is as effective as that of classical stuck-at fault-based diagnosis, when the latter applies, but is far more general. In particular, it can diagnose fails caused by bridges and opens as well as fails caused by regular stuck-at faults.

Abstract: Modern processors and SoCs require the adoption of power-oriented design styles, due to the implications that power consumption may have on reliability, cost and manufacturability of integrated circuits featuring nanometric technologies. And the power problem is further exacerbated by the increasing demand of devices for mobile, battery-operated systems, for which reduced power dissipation is mandatory. A large fraction of the power consumed by a synchronous circuit is due to the clock distribution network. This is for two reasons: First, the clock nets are long and heavily loaded. Second, they are subject to a high switching activity.The problem of automatically synthesizing a power efficient clock tree has been addressed recently in a few research contributions. In this paper, we introduce a methodology in which low-power clock trees are obtained through aggressive exploitation of the clock-gating technology. Distinguishing features of the methodology are: (i) The capability of calculating powerful clock-gating conditions that go beyond the simple topological search of the RTL source code. (ii) The capability of determining the clock tree logical structure starting from an RTL description. (iii) The capability of including in the cost function that drives the generation of the clock tree structure both functional (i.e., clock activation conditions) and physical (i.e., floorplanning) information. (iv) The capability of generating a clock tree structure that can be synthesized and routed using standard, commercially-available back-end tools.We illustrate the methodology for power-aware RTL clock tree planning, we provide details on the fundamental algorithms that support it and information on how such a methodology can be integrated into an industrial design flow. The results achieved on several benchmarks, as well as on a real design case demonstrate the feasibility and the potential of the proposed approach.

Abstract: A reversible gate has the equal number of inputs and outputs and one-to-one mappings between input vectors and output vectors; so that, the input vector states can be always uniquely reconstructed from the output vector states. This correspondence introduces a reversible full-adder circuit that requires only three reversible gates and produces least number of "garbage outputs ", that is two. After that, a theorem has been proposed that proves the optimality of the propounded circuit in terms of number of garbage outputs. An efficient algorithm is also introduced in this paper that leads to construct a reversible circuit.

Abstract: With larger chip images and increasingly aggressive technologies, key design processes must interoperate, PDS, a physical-synthesis system, accomplishes technology closure through interacting processes of logic optimization, placement, timing, clock insertion, and routing, all using a common infrastructure with robust variable-accuracy analysis abstractions.

Abstract: Single-flux quantum logic (SFQ) circuits, in which a flux quantum is used as an information carrier, have the possibility for opening the door to a new digital system operated at over 100-GHz clock frequency at extremely low power dissipation. The SFQ logic system is a so-called pulse logic, which is completely different from the level logic for semiconductors like CMOS, so circuit design technologies for SFQ logic circuits have to be newly developed. Recently, much progress in basic technologies for designing SFQ circuits and operating circuits at high speeds has been made. With advances in these design tools, large-scale circuits including more than several thousand junctions can be easily operated with the clock frequency of more than several tens of gigahertz. High-end routers and high-end computers are possible applications of SFQ logic circuits because of their high throughput nature and the low power dissipation of SFQ logic. In this paper, recent advances of SFQ circuit design technologies and recent developments of switches for high-end routers and microprocessors for high-end computers that are considered possible applications for SFQ logic will be described.

Abstract: Dual-rail encoding, return-to-spacer protocol and hazard-free logic can be used to resist differential power analysis attacks by making the power consumption independent of processed data. Standard dual-rail logic uses a protocol with a single spacer, e.g. all-zeroes, which gives rise to power balancing problems. We address these problems by incorporating two spacers; the spacers alternate between adjacent clock cycles. This guarantees that all gates switch in each clock cycle regardless of the transmitted data values. To generate these dual-rail circuits an automated tool has been developed. It is capable of converting synchronous netlists into dual-rail circuits and it is interfaced to industry CAD tools. Dual-rail and single-rail benchmarks based upon the Advanced Encryption Standard (AES) have been simulated and compared in order to evaluate the method.

Abstract: The clock generation and distribution system for the 130-nm Itanium 2 processor operates at 1.5 GHz with a skew of 24 ps. The Itanium 2 processor features 6 MB of on-die L3 cache and has a die size of 374 mm/sup 2/. Fuse-based clock de-skew enables post-silicon clock optimization to gain higher frequency. This paper describes the clock generation, global clock distribution, local clocking, and the clock skew optimization feature.

Abstract: This paper presents a circuit fault detection and isolation technique for quasi delay-insensitive asynchronous circuits. We achieve fault isolation by a combination of physical layout and circuit techniques. The asynchronous nature of quasi delay-insensitive circuits combined with layout techniques makes the design tolerant to delay faults. Circuit techniques are used to make sections of the design robust to nondelay faults. The combination of these is an asynchronous defect-tolerant circuit where a large class of faults are tolerated, and the remaining faults can be both detected easily and isolated to a small region of the design.

Abstract: Methods and apparatus are described relating to a system-on-a-chip which includes a plurality of synchronous modules, each synchronous module having an associated clock domain characterized by a data rate, the data rates comprising a plurality of different data rates. The system-on-a-chip also includes a plurality of clock domain converters. Each clock domain converter is coupled to a corresponding one of the synchronous modules, and is operable to convert data between the clock domain of the corresponding synchronous module and an asynchronous domain characterized by transmission of data according to an asynchronous handshake protocol. An asynchronous crossbar is coupled to the plurality of clock domain converters, and is operable in the asynchronous domain to implement a first-in-first-out (FIFO) channel between any two of the clock domain converters, thereby facilitating communication between any two of the synchronous modules.

Abstract: A clock control circuit includes a multiphase clock generating circuit receiving an output signal of a input buffer for generating multiphase clocks; a selector circuit receiving multiphase clocks output from the multiphase clock generating circuit for selecting one of the multiphase clocks; a first variable delay circuit for delaying the output of the selector circuit; a clock buffer dummy receiving the output signal of the variable delay circuit; a phase comparator circuit for detecting a phase difference between an output from the multiphase clock generating circuit and an output of the clock buffer dummy; and a filter for smoothing the output of the phase comparator circuit The first variable delay circuit has its delay time varied by the output of the filter The clock control circuit further includes a second variable delay circuit, receiving the output signal of the input buffer, having its delay time varied by the output of the filter; an adder circuit for adding the filter output and an input set value; a third variable delay circuit, receiving the output signal of the input buffer, having its delay time varied by the output of the adder circuit; and clock buffers receiving output signals of respective ones of the second and third variable delay circuits

Abstract: In processors having multiple cores, such as CMPs, an independent MISR test pattern compression circuit is provided for each logic block, which makes it possible to perform LSI tests more efficiently. A processor includes a plurality of logic block circuits, which include at least a first processor core circuit and a second processor core circuit, each processor core circuit having a scan chain circuit and being operable independently, and a common block circuit having a scan chain circuit and a cache circuit that is shared by the first processor core circuits and the second processor core circuits. The processor further includes, for each logic block, a test pattern generating circuit operable to generate a test pattern and input the test pattern to the scan chain of each logic block circuit, and a test pattern compression circuit operable to accept as input and compress the test pattern output by the scan chain of each logic block circuit.

Abstract: A synchronous clock signal is generated in a large number of local clock circuits at the same time by exposing photoconductive regions in each local clock circuit to a pulsed light source that operates at a fixed frequency. The photoconductive regions generate photoconductive currents which are sufficient to cause a logic inverter to switch states.

Abstract: A compensation circuit and method for compensating for variations in time delay adjustments of synchronizing circuits that synchronize an external clock signal applied to an integrated circuit with internal clock signals generated in the integrated circuit in response to the external clock signal. The time delay relationship between fine and coarse delay circuits of an adjustable delay circuit is adjusted to compensate for variations from an expected time delay relationship.

Abstract: We introduce a simple model for calculating transistor sizes of an asynchronous control circuit. The model builds on the theory of logical effort and relates transistor sizes to the speed and energy consumption of a circuit. We show how to calculate transistor sizes quickly, how to calculate the speed limit of a circuit, and how to compare circuits in terms of energy-versus-speed independent of a process technology. We compare three asynchronous control circuits for a FIFO: a chain of C-elements, an asP control, and a GasP control.

Abstract: A random binary sequence generator (105) for generating a random binary sequence (RRBS) adapted to be used for producing random numbers, comprising at least one logic circuit (115) corresponding to an associated finite-state machine having a statetransition function including states arranged to form cycles of states, wherein: the at least one logic circuit has a set of logic circuit inputs (In) and a set of logic circuit outputs (Out) fed back to said logic circuit inputs; the associated finite-state machine is autonomous and asynchronous; the state-transition function is void of loops; and any of the cycles of states has either a minimum length equal to three states, in case the cycle is stable, or a minimum length of two states, in case the cycle is meta-stable.

Abstract: An integrated circuit comprises a first circuit that receives a clock signal. A first temperature sensor senses a first temperature. Non-volatile memory that communicates with the first temperature sensor outputs calibration data as a function of the first temperature. A semiconductor oscillator that communicates with the non-volatile memory and the first circuit generates the clock signal having a frequency that is related to the calibration data. A select input selects the frequency of the output signal as a function of an external passive component.

Abstract: Techniques or designs of circuits to correct distortions in signals transported over a high-speed digital connection between a video source (e.g., a PC or a DVD player) and a digital monitors (such as LCDs) are disclosed. According to one aspect of the present invention, a distorted signal is corrected by an interface circuit that oversamples the incoming signal with clock pulses or signals generated using a phase lock loop (PLL) from a clock seed signal. These clock signals possess different phases that are shifted from each other. In order to support a wide range of data rate, a programmable DPLL is used to produce a number of different ranges of clock frequency (e.g., 4 ranges). In addition, to avoid data phase shift, a delay locked loop (DLL) is used to compensate for the phase shift. A phase detection logic is also used to extract phase information from the over-sampled data. The phase information is fed back to the DLL.

Abstract: Novel gate-diffusion input (GDI) circuits are applied to asynchronous design. A variety of GDI implementations are compared with typical CMOS asynchronous circuits. Dynamic GDI state holding elements are 2/spl times/ smaller than CMOS C-elements, 30% faster, and consume 85% less power, but certain CMOS elements are preferred when static storage is called for. A GDI bundled controller outperforms CMOS on all accounts, having 1/3 the delay and requiring less than half the area while consuming the same power. A combination CMOS-GDI circuit provides the optimal solution for qDI combinational logic, saving 1/3 the power, half the area, and 10% in delay relative to a CMOS implementation. GDI circuits also provide some measure of enhanced hazard tolerance.

Abstract: A frequency-voltage mechanism for power management including first and second PLLs, select logic, control logic, and voltage control logic. The first PLL generates a first source clock signal at a first frequency based on a bus clock signal. The second PLL generates a second source clock signal at a second frequency based on a first frequency control signal and the bus clock signal. The select logic selects between the first and second source clock signals to provide a core clock signal based on a select signal. The clock control logic detects power conditions via at least one power sense signal, provides the first frequency control signal according to power conditions, and provides the select signal. The voltage control logic adjusts the operating voltage commensurate with frequency of the core clock signal. Power consumption is dynamically adjusted without undue delay while providing significant power efficiency benefits.

Abstract: A pseudo-synchronous temporary storage element transports data between two system blocks with different clock systems by pseudo-synchronizing the clock edges of the two clock signals. The pseudo-synchronization circuit may be an integral part of a storage element, a separate pseudo-synchronization device, or a discrete add-on circuit to an off the shelf storage element device.

Abstract: A delay circuit includes a first delay line circuit having a plurality of stages of delay units, a second delay line circuit having a plurality of stages of delay units, a plurality of transfer circuits provided in association with respective stages of the delay units of the first delay line circuit, the transfer circuits controlling the transfer of the outputs of the delay units of the first delay line circuit to associated stages of the delay units of the second delay line circuit. The delay units of respective stages of the first delay line circuit inverting input signals. Each stage delay unit of the second delay line circuit includes a logic circuit receiving an output signal of the transfer circuit associated with the delay unit in question and an output signal of a preceding stage to send an output signal to a following stage. The duty ratio is rendered variable by independently selecting the rising edge of the input signal and a propagation path of the falling edge.

Abstract: An integrated circuit comprising: at least one active device that outputs light during a change in state of the at least one device during operation; a clock circuit configured to output a clock signal to the at least one active device, the clock signal rate being varied so as to hinder optical detection of a pattern of the light during operation of the at least one active device.