### Low Power Asynchronous. Digital Signal Processing

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The throughput of the MAC can be expressed as. In above Eq. The architecture selection for MAC unit generally depends upon the type of applications. For embedded microprocessor or microcontroller applications the memory usage is limited and the operand size is also small and therefore, recursive architecture is suitable, when power and area is important.

For high performance applications like notepads, laptops and desktops require large set of data computation therefore parallel architecture will be suitable. To perform multi-mode logic dependent operation, where the speed and power constraint is considered then shared segmented architecture is preferable, which is mainly used in embedded medical equipments and in communication systems, such as Orthogonal Frequency Division Multiplexing OFDM based wireless devices, subcarrier frequency domain operations, channel estimator and carrier synchronizer.

The implementation of MAC structure using FPGAs will have limited resources and fixed logic technology while in ASIC it is semi-custom or full custom so that optimization can be achieved from the architectural level to transistor level. The macrocell was fabricated using 0. The SA-FF technique acts as a sense amplifier to regenerate low-swing differential inputs.

Another important speed optimization was achieved by using moderately scaled PMOS devices in the swing restoring network. A novel recursive MAC unit which offers single cycle throughput for 16 bit X 32 bit operation for audio processing application has been proposed by Clark et al.

The circuit dissipated mV operating at MHz for 1.

## Low Power Asynchronous Digital Signal Processing

The proposed core was the first application of the Intel Xscale micro architecture. The PP and summation has been implemented using, Booth encoding and four stages Wallace tree. Bit slice operations were performed by the MAC unit for the first clock cycle of 16 bit data of multiplier and multiplicand and the same is encoded through the Booth multiplier and compressed through Wallace tree and the resultant were accumulated.

During the second clock cycle the remaining 12 bit was encoded and added with CLA. The functional block has been implemented using static CMOS logic. The final stage of addition operation has been constructed using, conditional-sum addition that incorporates Parallel Prefix Structure PPS. The synchronization of clock circuit has been implemented with single rail domino logic. A 32 bit recursive MAC has been proposed by Liao and Roberts , incorporates a new mixed-length encoding scheme using; four-stage Wallace tree to improve performance and power.

The PPG and PPRT were implemented using Booth multiplier, which utilizes 16 bit encoding scheme to generate the last sum and carry vectors in two cycles. The power-saving techniques employed in this MAC unit were clock gating and pulse-clocking methods. The compression network utilizes rounding and truncation approach to minimize the switching activity of unused logic to reduce the power dissipation. The detection circuit identifies the active inputs and appropriately deactivates the unused components and bits. The performance of the MAC unit has been improved in the generation of PP using radix-4 modified Booth encoding scheme which involves overlapping groups of three bits at single encoding thereby reducing the PPG time.

In the first stage, Booth encoder accepts 32 bit inputs of multiplier and multiplicand and produces 17 PPs. The second stage receives 3 inputs at a time, 2 inputs from stage one compressed PP and third input of size 72 bit from external register. By this method the proposed MAC unit eliminates the need of adders in stage 1 thereby reducing the area cost and power dissipation. The final stage adder has been constructed by CSA.

The interlock pipeline block consists of asynchronous-to-asynchronous and parallel synchronous timing path. These two clocks were used to acknowledge and validate the MAC operation. A high-speed parallel MAC has been propounded by Kashfi et al.

## A low-power asynchronous ECG acquisition system in CMOS technology.

The full swing restoration has been achieved through Sense Amplify SA connected at the output side. This technique utilizes LVS operation in the internal nodes and establishes full swing at the output node using SA thereby power reduction has been achieved. The improved booth encoding scheme was accomplished in two stages specifically encoding and selection. A 16 bit parallel MAC has been proposed by Wang et al. The power reduction in the MAC unit has been achieved by using, reversible logic by recycling the charge stored in the internal capacitances.

The MAC deploys Modified radix Booth encoding scheme, where 3 bit are encoded at a time with 1 bit overlapping and the PPs are compressed using Wallace tree. The final adder stage has been constructed using Ladner-Fischer parallel prefix adder. The MAC proposed by Xia et al. The speed of the MAC has been improved through a novel 1-A partial product compression circuit based on interleaved adders. This MAC supports 32 bit multiplication, 16 bit multiply or MAC operation and two ways parallel multiply operations at a frequency of 1.

A multi-mode high performance MAC unit which supports both true and complementary inputs with a special feature incorporates accumulation guard bits for saturation circuit has been propounded by Hoang et al.

The functional component has been constructed using Booth multiply and Wallace tree compression which incorporates CMOS logic. The existing MAC structure is shown in Fig. The circuit detects the input voltage lower than mV and differentially boost the low-swing voltage to full rail-to-rail voltage by using Sense Amplifier SA.

The circuit receives two inputs true and complementary low swing voltage which will be boosted and the same is latched in Flip-Flop FF. The main shortfall associated with this technique is that the timing signal used to activate the SA is mostly from delay lines using self-timing which should be properly adjusted and optimized, otherwise there will be a risk of fatal malfunction or the system hangs in metastability state or in the worst case racing signal hazards may encounter.

The behaviour of the circuit is similar to conventional FF, when the clock have the transition from it acts as master FF and stores the differential output to latch and during the slave device is activated which passes the output Q and. The gate input of each transistors are connected with control inputs variables and the drain terminal of each transistors in the logic network are connected with pass inputs variables.

But the problem incurred with this configuration is leakage current through static inverters. In SRPL when proper device scaling is not provided then discharging the output from transition becomes bottleneck and consequently the output degrades. Static complementary metal oxide semiconductor: The logic style reported by Clark et al. Nevertheless, the contribution of power dissipation in CMOS logic is determined by the operating frequency.

When the input load is high the power consumption and leakage is very high due to large PMOS devices. The level restoration is achieved using static CMOS inverters, which produce true and complementary outputs. The PMOS latch connected below the static inverters decreases the static power dissipation. The CPL offers the highest speed at the expense of increased transistor count. The other shortfall of this logic utilizes significant number of nodes and wiring complexity is high. The LVS logic circuit realization is shown in Fig.

The complementary inputs are generated using static inverters in the first stage and these inputs are fed to second stage DCN which is constructed using NMOS transistor to evaluate the logic function under two control signals namely CTL and Reset. These differential outputs are boosted using SA in stage 3.

The non-zero offset level of SA zero output induces glitches which are compensated through CDL at the last stage. This unit not only reduces the glitches but also increase the gain of the output signal. The circuit utilizes two power clocks and The logic function is evaluated using cross coupled transmission gates.

The functional computation of CTGAL is alienated into two phases specifically sampling and valuing-holding-recovery phase. The input signals are sampled via the NMOS transistors N1 and N2 which are triggered with the input clock During the second phase, when the input and power clock are at logic zero either node x or y will be floated high-voltage of VDD-V tn.

At the same time the floating node will bootstrap the voltage level high through the charged internal node capacitances and hold this phase. The output of the circuit is full swing due to energy recovery mechanism. Multiplier scheme for MAC unit: Multiplication is an essential arithmetic operation of MAC block which have huge area, extended latency and consume substantial power.

As avowed in Yeh et al. Therefore, low-power multiplier design has been an significant part in low-power VLSI system design. The speed and power consumption of multiplier depends on the algorithm for PPG, PPA and logic technology used to design the multiplier cell.

The power saving in multiplier cells are accomplished with two approaches.

They are; High-level algorithms to decrease the switching activity and the regularity of structure block and interconnect complexity. The multiplication algorithms are classified based on the space area complexity, interconnect and time complexity. In terms of PPG and PPA the multipliers are categorized into distributed arithmetic, parallel, serial-parallel, complementary Booth encoding , Wallace using CSA, row-column bypass, modulo diminishing -1 and wave pipelining multipliers. The general multiplier schemes deployed in MAC unit are distributed arithmetic, parallel, complementary Booth encoding , Wallace using CSA and wave pipelining methods.

The multiplier scheme in Matsui et al. The general merits of these schemes are reduced power consumption and area. This type of multiplier is apparently very slow due to its bit-serial characteristics.

## Design of a Low–Power Embedded Processor Architecture Using Asynchronous Function Units

The multiplier scheme in Parameswar et al. The interconnect complexity can be reduced using Dadda multiplication algorithm Dadda, ; Townsend et al. But the complexity of this circuit is very high due to the presence of shifter and encoder. The power factor is also affected due to irregular interconnects.

The multiplier design in Chang et al. The MAC design by Matsui et al. The delay of RCA linearly increases as the number of input n increases, therefore, the speed-power factor of the RCA is limited when n grows higher. The adder scheme by Parameswar et al. The MAC unit in Matsui et al. The adder scheme by Clark et al. The short fall in this scheme is fan-out limitation owing to the large number of multiplexer unit. The adder design in Clark et al. The circuit complexity of multipliers and adders used in the design of MAC is shown in Table 1 and 2.

The performance characteristics of various MAC structure is listed in Table 3. The bird eyes view of existing MAC architecture has been presented. Are you sure you want to Yes No. Be the first to like this. No Downloads.

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### 1 Introduction

Martin, California Institute of Technology 4. Adopted from: Alain J. Martin, California Institute of Technology 5. Custom Design 6. NCL circuits utilize dual-rail or quad-rail logic to achieve delay- insensitivity. Enable the circuit State Retention i. In between the clock ticks, signals may exhibit hazards and may make multiple transitions as combo circuit stabilizes. The absence of clock means signals are valid all the time, every transition has a meaning and consequently any hazard and races must be avoided.

Truth Table for Muller C Element Preliminaries Impact of DVS The traditional EDA tools are merged together with asynchronous circuit design, and the wrapper only has standard cells but not special asynchronous logic gates. The simulation and verification were made by Modelsim and Quartus respectively, and the results have shown that the GALS system works properly and has a preferable performance. Abstract: In order to improve voltage utilization ratio and dynamic performance of frequency converter, this paper presents a digital frequency converter design scheme based on digital signal processor TMSLFA and the theory of space vector pulse width modulation SVPWM technology, provides its detailed design measures of software and hardware and SVPWM algorithm realization methods.

The experimental results prove that this new frequency converter has simple structure, high control precision, higher voltage utilization ratio, better dynamic and static property. Authors: Jing Liu. Abstract: Considering the characteristics of vector control system, a speed controller based on fuzzy logic is presented in this paper. Using the fuzzy reasoning, we can update the output of the speed controller real time and handle the uncertain information.

Results of simulation are provided to demonstrate that the vector control system of asynchronous motor based on fuzzy controller not only has the feature of simple and easy to be implemented, but also has the dynamic performance and robustness. An asynchronous 4-bit successive approximation SAR quanztizer is employed to digitize the analog input. Inherent summation of SAR quantizer is utilized as analog summation.

The switched operational amplifier is used in first integrator to reduced power consumption. The modulator, simulated at the transistor level using 0. Abstract: The detection of motor noise can be used to evaluate the condition of motor. Furthermore the detection of motor noise can be used to analyze the source of motor noise and is helpful to reduce the motor noise. Through analyzing the mechanism of motor noise, a laptop computer and LabVIEW software are used to design the experimental system.

The hardware of noise detection system consists of an external microphone and sound card coming with the computer. LabVIEW is used to detect the noise signal and record the noise and realize the spectrum analysis. Through detecting and analyzing the noise of the permanent magnet DC motor and three-phase asynchronous motor, It is proved that the motor noise experimental system consisting of computer and LabVIEW can fully meet the requirements of electrical machine test and research.