Soft Error Tolerant Carry-Select Adders Implemented into Altera FPGAs

Single event upset mitigation by means of a sequential circuit state freeze

Estimating the frequency of the elements in a data set is commonly needed in data analysis. With the increase of the size of the data sets, accurately computing the number of times that each element appears with a counter becomes impractical. Instead, the Count Min Sketch (CMS) is widely used in big data processing to estimate frequency due to its simplicity and small storage needs. However, soft errors caused by Single Event Transients (SETs) will affect the hardware implementation of the CMS, mainly the hash functions. In this paper, the effect of SETs on the hash functions of the CMS frequency estimate is analyzed theoretically in terms of overestimation probability, underestimation probability, and the equal probability, and further discussed for data with different frequency. Simulation results verify the correctness of the theoretical analysis and reveal several valuable conclusions. First, a large portion of SETs can be tolerated by the CMS itself, and the reliability of the CMS improves when larger number of arrays are used. Second, the average probability for overestimation and underestimation are almost the same, and decrease for larger numbers of arrays. Third, SETs are more likely to cause underestimation for the most frequent data elements. Finally, the overall effect of SETs on the CMS is slightly affected by the number of counters in each array, and seems to be independent of the distribution of the input sequence. The results and analysis presented in this paper provide a starting point for the design of efficient SET fault-tolerant schemes for the CMS.

Carry select adder (CSLA) one of the fastest adders used in complex data processing to perform fast arithmetic functions. Minimum amount of power consumption is a major driving force behind the development of CMOS technologies. From the structure of CSLA it is clear that there is scope for reducing the area & power consumption in the CSLA. In this paper 8T full adder is used as a building block for 8-bit SQRT CSLA. 8T full adder is designed by XNOR-XNOR hybrid CMOS design. Based on this modification, 8-, 16-, 32-, 64-bit SQRT CSLA architecture has been developed & compared with the regular SQRT CSLA. Binary to Excess one converter (BEC) based CSLA are analyzed to study the data dependence & to identify all redundant logic operations. In this paper, all the redundant logic operations in the conventional CSLA are eliminated and a new logic formulation where carry select operation is scheduled before the calculation of final sum is proposed. Gate Diffusion Input (GDI) technique of low power digital combinatorial circuit design is also described. The frequency of operation is 5 MHZ. This work estimates the performance of the proposed design with the regular design in terms of area & power through the logic design & layout in 250nm CMOS process technology & implemented using Tanner (S-Edit) tool. The result analysis shows that the proposed structure is better than the conventional CSLA.

In this paper we describe the fault injection models for the systems tolerant to the single event upsets (SEU) and single event transients (SET). The presented fault modelling approach is based on the random generated SEU faults in sequential logic and SET faults in combinational logic. The fault injection models for triple modular redundant (TMR) and dual modular redundant (DMR) circuits are developed in order to simulate the fault-tolerant systems. The analytical models for calculation of the probability of failure-free TMR and DMR circuits are defined too. To justify the reduced redundancy concept, the simulated and calculated probabilities of failure-free TMR and DMR circuits are presented and discussed. The obtained results show a better trade-off between hardware overhead and circuit failure-free probability of the DMR concept.

A single event transient (SET) filtering technique for non-volatile field programmable gate arrays (FPGAs) are investigated experimentally using the AND-OR-Multiplexer SET filter technique. The technique combines AND – OR gate circuits in parallel with a two input multiplexer to provide a single circuit that can dissipate SETs irrespective of whether the input state is high or low. This paper presents the results of the experimental investigation, with the SET filter applied to various sequential circuit configurations in a commercial Flash-based FPGA, the 0.13-μm ProASIC3E product family (A3PE), by proton beam irradiation. Their implementation and evaluation in-beam show their efficiency in eliminating SETs and single event upsets (SEU) compared to unmitigated designs.

Computational speed of basic data path elements such as adders plays a crucial role in performance of digital and signal processing systems. Among various adder architectures, carry select adder (CSLA) has better performance in terms of speed in comparison with others. However, this merit is accompanied by its high power dissipation and area occupancy due to redundant computing elements used in each stage hence limiting its application. Power dissipation in these adders can be minimized by various low power implementation techniques such as reversible logic gates, multi-V th approach, and adiabatic logic. Among these low power approaches, adiabatic logic proves to be more efficient in comparison with other low power approaches. In the proposed work, 180 nm CMOS technology in CADENCE environment is used to carry out the design and analysis of both conventional and proposed CSLA architectures. Power dissipation in this proposed 8-bit CSLA architecture reduces by about 82% as compared to conventional 8-bit CSLA adder architecture. Further, the computational delay is also reduced when compared with the conventional 8-bit CSLA architecture. It is noteworthy that delay in adiabatic logic circuits greatly depends on frequency of operation [1].

Due to scaling induced effects, CMOS circuits become increasingly more sensitive to transient pulses caused by single event (SE) particles. Researchers mostly considered SE transients as the main cause for combinational logic (CL) related radiation-induced soft errors. However, for high-reliability applications such as avionics, military and medical applications, additional sources such as SE induced soft delays, clock jitters, false clock pulses and crosstalk effects need to be included in soft-error reliability analysis. As technologies advance, coupling effects among interconnects increasingly cause SE transients to contaminate electronically unrelated circuit paths, which can in turn increase the "SE susceptibility" of CMOS circuits. This work focuses on such coupling induced soft error mechanisms in CL, namely the SE crosstalk noise and delay effects. An attempt has been made to compare SE crosstalk noise and SE transient effects, and crosstalk contribution to soft error rate has been examined. In addition, the SE induced coupling delay effect has been studied and compared to radiation induced soft delay effect for various technologies. Results show that, in newer technologies, the SE coupling delay becomes quite comparable to soft delay effect, although caused indirectly by cross-coupling effects. In comparisons, the distributed nature of interconnects has been taken into account and results are demonstrated using HSPICE simulations with interconnect and device parameters derived in 130, 90 and 65 nm technologies.

Single event transients (SETs) stand out as one of the major causes of soft errors in nanoscale CMOS integrated circuits. To reduce the need for exhaustive circuit simulations in the design of radiation-hard integrated circuits, the cost-effective approaches for characterization and modeling of SET generation effects in standard logic cells are required. In this work, a SPICE-based methodology for characterization of SET generation effects, employing two different SET current models, is presented. Based on the acquired simulation results, the empirical models for the two main SET generation metrics (SET critical charge and SET pulse width) are derived. The SET generation models and the respective model parameters are intended to be used as inputs for the higher-level analysis of SET effects in digital circuits designed with the characterized standard logic cells. By storing the model parameters for each gate in the look-up table, instead of storing the raw data obtained from SPICE simulations, the amount of characterization data can be significantly reduced, allowing to speed up the subsequent SET analysis of a complex circuit.

This paper describes the deployment and optimization process of triple-module redundancy (TMR) under high design constraints against single-event upset (SEU) and single-event transient (SET). It includes modelling of single-event effect (SEE) pulses with TCAD mesh model, TMR deployment strategies, and verification methods. The simulation result shows that the prototype system with optimized TMR deployment has high reliability with respect to design requirements. The system can run for more than 5 years without critical errors with an equivalent error rate in the working environment is lower than 10$^{-9}$ .

Reliability means and radiation resistance of digital equipment. For aerospace computer systems is extremely urgent to develop radiation-resistant components. One way to ensure the radiation resistance is the creation of a special architecture — RHBD (Radiation Hardened by Design). This approach includes triple redundancy (Triple Modular Redundancy — TMR) to reduce radiation-induced switching of logic elements (Single Event Transients — SET) and memory elements (Single Event Upset — SEU). FPGA due to the large number of elements configuration memory is not vulnerable to the effects of radiation. Therefore, one-time programmable devices are used, for example, the companies Actel, but flip-flops tripled too. Nevertheless, in the SRAM configurable FPGA Virtex (Xilinx) used triple redundancy with Majority Vote Circuit based on a tristate buffer instead LUT. Such Voter has implementation features that are explored in the article. One of the variants of majority voter for the pins of the FPGA using a minority voting function. Only in this case, no conflict of signals at the outputs of buffers. Describes CMOS implementation of the voters. The paper proposes a fault tolerant CMOS implementation of the Majority Voter and Minority Voter in order to improve reliability and FPGA radiation resistance.

An SEU resilient, SET filterable and cost effective latch in presence of PVT variations

As the technology scales down, space radiation induced soft errors are becoming a critical issue for the reliability of Integrated Circuits (ICs). In this paper, we propose a novel layout-based Single-Event Transient (SET) injection approach to evaluate the Soft Error Rate (SER) of large combinational circuits in Complementary Metal-Oxide-Semiconductor (CMOS) bulk technology. We consider the effect of ion strike location on the SET pulse width in this approach. Heavy-ion experiments on two different inverter chains are conducted to verify this layout-based SET injection approach. The simulation and experiment results show that this approach can fairly reflect the SET pulse width distribution. Furthermore, we compare the soft error number calculated by our proposed layout-based approach with the normal SET injection approach, and illustrate the detailed circuit response obtained by our proposed approach.

This paper introduces a soft-error tolerant asynchronous ternary content-addressable memory (TCAM) based on a transistor/magnetic-tunnel-junction (MTJ) hybrid structure. An MTJ device that is often used for a non-volatile memory stores one-bit information as a resistance whose value is robust against alpha particle and atmosphere neutron strikes, which significantly lower the probability of single-event upsets (SEUs). The TCAM is also robust against delay variations caused by single-event transients (SETs) as it is designed based on four-phase dual-rail encoding realized using complementary NAND and NOR-type word circuits. The dual-rail TCAM cell is compactly designed using 20 transistors (20T) and 4 MTJ devices stacked on a CMOS layer as opposed to a single-rail 24T TCAM cell that consists of soft-error tolerant storage elements. In addition, soft errors can be detected using the dual-rail signals. As a design example, a 256-word x 64-bit TCAM is designed under a 90 nm CMOS/MTJ technology and is evaluated with a collected charge caused by a particle strike, which induces the SET and hence the delay variation. The proposed TCAM properly operates under the delay variation, while achieving comparable performance to a synchronous single-rail TCAM in which an up to 25% timing error occurs.

Single-event transients (SETs) threaten modern reliability-demanding SoCs equipped with error correction codes (ECC) for single event upset (SEU) mitigation. However, conventional gate-level SET fault injection (FI) remains prohibitively slow for practical reliability evaluation. This work presents Flawase, a high-throughput SET injection framework that enables comprehensive system-level evaluation of SET-induced soft errors. Flawase consists of two phases: a netlist-level inject-and-capture simulation, which systematically flips the output of every gate-cycle pair during program execution to record flipflop changes one cycle later, and a scan-chain-based replay-andmeasure emulation, which replays these patterns at hardware speed to quantify system-level impact. Implemented on an opensource RISC-V system, FIawase reduces a comprehensive SET injection campaign from decades of pure simulation to nearly a day, achieving over four orders of magnitude end-to-end speedup. Flawase takes a critical first step toward exhaustive, cycle-accurate SET analysis, enabling architectural and reliability research at previously infeasible scales.

PurposeThe purpose of this paper is to present a transition detector (TD)-based radiation hardened flip-flop (TDRH-FF) for single event upset (SEU).Design/methodology/approachWith SEU recovery and single event transient (SET) detector mechanism, the TDRH-FF can tolerate SEU during hold mode and generate a warning signal for architecture-level recovery during transport mode when input signal contains SET. Evaluation results show that the TDRH-FF outperforms comparable comprehensive performance.FindingsSimulation results show that 1) the mean pulse width of the correction glitches (at full width half maximum) of TDRH-FF is less than 10 ps; 2) the area overhead of TDRH-FF is similar to the EVFERST-FF, BISER-FF and DNURHL-FF; 3) TDRH-FF has the same average power consumption as SETTOF, and moderate PDP and Ps values among these compared FFs.Originality/valueIn this paper, a TD-based TDRH-FF is proposed to solve the problems in the previous design. And the main contributions of the proposed TDRH-FF are summarized: Minimum size transistors are used in the proposed TD which leads to a considerable decrease in area overheads and propagation delay (resulting in an ignorable correction glitch); and compared with other radiation hardened flip-flop, TDRH-FF outperforms comparable comprehensive performance.