Modified Level Restorers Using Current Sink and Current Source Inverter Structures for BBL-PT Full Adder

Full adder is an essential component for the design and development of all types of processors like digital signal processors (DSP), microprocessors etc. In most of these systems adder lies in the critical path that affects the overall speed of the system. So enhancing the performance of the 1-bit full adder cell is a significant goal. In this paper, we proposed two modified level restorers using current sink and current source inverter structures for branch-based logic and pass-transistor (BBL-PT) full adder [1]. In BBL-PT full adder, there lies a drawback i.e. voltage step existence that could be eliminated in the proposed logics by using the current sink inverter and current source inverter structures. The proposed full adders are compared with the two standard and well-known logic styles, i.e. conventional static CMOS logic and Complementary Pass transistor Logic (CPL), demonstrated the good delay performance. The implementation of 8-bit ripple carry adder based on proposed full adders are finally demonstrated. The CPL 8-bit RCA and as well as the proposed ones is having better delay performance than the static CMOS and BBL-PT 8-bit RCA. The performance of the proposed BBL-PT cell with current sink & current source inverter structures are examined using PSPICE and the model parameters of a 0.13 µm CMOS process

Area/latency optimized early output asynchronous full adders and relative-timed ripple carry adders

This article presents two area/latency optimized gate level asynchronous full adder designs which correspond to early output logic. The proposed full adders are constructed using the delay-insensitive dual-rail code and adhere to the four-phase return-to-zero handshaking. For an asynchronous ripple carry adder (RCA) constructed using the proposed early output full adders, the relative-timing assumption becomes necessary and the inherent advantages of the relative-timed RCA are: (1) computation with valid inputs, i.e., forward latency is data-dependent, and (2) computation with spacer inputs involves a bare minimum constant reverse latency of just one full adder delay, thus resulting in the optimal cycle time. With respect to different 32-bit RCA implementations, and in comparison with the optimized strong-indication, weak-indication, and early output full adder designs, one of the proposed early output full adders achieves respective reductions in latency by 67.8, 12.3 and 6.1 %, while the other proposed early output full adder achieves corresponding reductions in area by 32.6, 24.6 and 6.9 %, with practically no power penalty. Further, the proposed early output full adders based asynchronous RCAs enable minimum reductions in cycle time by 83.4, 15, and 8.8 % when considering carry-propagation over the entire RCA width of 32-bits, and maximum reductions in cycle time by 97.5, 27.4, and 22.4 % for the consideration of a typical carry chain length of 4 full adder stages, when compared to the least of the cycle time estimates of various strong-indication, weak-indication, and early output asynchronous RCAs of similar size. All the asynchronous full adders and RCAs were realized using standard cells in a semi-custom design fashion based on a 32/28 nm CMOS process technology

Lightweight Architectures for Reliable and Fault Detection Simon and Speck Cryptographic Algorithms on FPGA

The widespread use of sensitive and constrained applications necessitates lightweight (lowpower and low-area) algorithms developed for constrained nano-devices. However, nearly all of such algorithms are optimized for platform-based performance and may not be useful for diverse and flexible applications. The National Security Agency (NSA) has proposed two relatively-recent families of lightweight ciphers, i.e., Simon and Speck, designed as efficient ciphers on both hardware and software platforms. This paper proposes concurrent error detection schemes to provide reliable architectures for these two families of lightweight block ciphers. The research work on analyzing the reliability of these algorithms and providing fault diagnosis approaches has not been undertaken to date to the best of our knowledge. The main aim of the proposed reliable architectures is to provide high error coverage while maintaining acceptable area and power consumption overheads. To achieve this, we propose a variant of recomputing with encoded operands. These low-complexity schemes are suited for lowresource applications such as sensitive, constrained implantable and wearable medical devices. We perform fault simulations for the proposed architectures by developing a fault model framework. The architectures are simulated and analyzed on recent field-programmable grate array (FPGA) platforms, and it is shown that the proposed schemes provide high error coverage. The proposed low-complexity concurrent error detection schemes are a step forward towards more reliable architectures for Simon and Speck algorithms in lightweight, secure applications

Reliable Low-Latency and Low-Complexity Viterbi Architectures Benchmarked on ASIC and FPGA

The Viterbi algorithm is commonly applied in a number of sensitive usage models including decoding convolutional codes used in communications such as satellite communication, cellular relay, and wireless local area networks. Moreover, the algorithm has been applied to automatic speech recognition and storage devices. In this thesis, efficient error detection schemes for architectures based on low-latency, low-complexity Viterbi decoders are presented. The merit of the proposed schemes is that reliability requirements, overhead tolerance, and performance degradation limits are embedded in the structures and can be adapted accordingly. We also present three variants of recomputing with encoded operands and its modifications to detect both transient and permanent faults, coupled with signature-based schemes. The instrumented decoder architecture has been subjected to extensive error detection assessments through simulations, and application-specific integrated circuit (ASIC) [32nm library] and field-programmable gate array (FPGA) [Xilinx Virtex-6 family] implementations for benchmark. The proposed fine-grained approaches can be utilized based on reliability objectives and performance/implementation metrics degradation tolerance

Age-Acknowledging Reliable Multiplier Design with Adaptive Hold Logic

Digital multipliers are among the most critical arithmetic functional units. The overall performance of these systems depends on the throughput of the multiplier. Meanwhile, the negative bias temperature instability effect occurs when a pMOS transistor is under negative bias (Vgs = −Vdd), increasing the threshold voltage of the pMOS transistor, and reducing multiplier speed. A similar phenomenon, positive bias temperature instability, occurs when an nMOS transistor is under positive bias. Both effects degrade transistor speed, and in the long term, the system may fail due to timing violations. Therefore, it is important to design reliable high performance multipliers. In this paper, we propose an aging-aware multiplier design with novel adaptive hold logic (AHL) circuit. The multiplier is able to provide higher throughput through the variable latency and can adjust the AHL circuit to mitigate performance degradation that is due to the aging effect. Moreover, the proposed architecture can be applied to a column- or row-bypassing multiplier. The experimental results show that our proposed architecture with 16 ×16 and 32 ×32 column-bypassing multipliers can attain up to 62.88% and 76.28% performance improvement, respectively, compared with 16×16 and 32×32 fixed-latency column-bypassing multipliers. Furthermore, our proposed architecture with 16 × 16 and 32 × 32 row-bypassing multipliers can achieve up to 80.17% and 69.40% performance improvement as compared with 16×16 and 32 × 32 fixed-latency row-bypassing multipliers

16-bit Digital Adder Design in 250nm and 64-bit Digital Comparator Design in 90nm CMOS Technologies

High speed, low power, and area efficient adders and comparators continue to play a key role in hardware implementation of digital signal processing applications. Adders based on Complimentary Pass Transistor Logic (CPL) are power and area efficient, but are slower compared to Square Root Carry Select (SQRT-CS) based adders. This thesis demonstrates a unique custom designed 16-bit adder in 250-nm CMOS technology to obtain fast and power/area efficient features by combining CPL and CS logic. Comparing the results obtained for proposed 16-bit Linear CPL/CS adder with the BEC (Binary Excess-1 Code) based low power SQRT-CS adder, the delay is reduced by approximately one thirds, power is reduced by 19.2%, and the number of transistors is reduced by 23.4%. Also, new tree-based 64-bit static and dynamic digital comparators are presented in this thesis to perform high speed and low power operations. This tree-based architecture combines a new approach of designing dynamic comparator using a low duty cycle clock to reduce the short circuit power consumption in pre-charge (or pre-discharge) mode. This work also introduces a new sizing strategy and load balancing techniques to improve self-pipelining tendency of a tree based design. A resource sharing technique is also integrated in both static and dynamic comparator designs. At 1.2V power supply in CMOS 90nm technology, worst path delay and worst power are 374ps and 822µW, respectively for low cost static design with 1244 (768+476) transistors in total. 768 transistors are used for resource sharing. The proposed full and partially dynamic designs show superior power efficiency compared to recent state of art designs. The worst power consumptions at 5GHz and 25% (50ps) duty cycle clock for the 64-bit full and partially dynamic comparator designs are 5.00mW and 2.78mW, respectively. 769 (320+449) transistors includes 320 transistors for resource sharing, and 1217 (768+449) includes 768 transistors for resource sharing for full and partial dynamic comparators, respectively