8-Bit Barrel Shifter That May Rotate the Data in Both Direction

Performance Analysis of Low Power CMOS based 8 bit Barrel Shifter

Deepti Shakya M-Tech VLSI Design SRCEM Gwalior (M.P) INDIA

Shweta Agrawal Assistant Professor, Dept. Electronics & Communication Engineering SRCEM Gwalior (M.P), INDIA Abstract

Barrel Shifter isimportant function to optimize the RISC processor, so it is used for rotating and transferring the data either in left or right direction. This shifter is useful in lots of signal processing ICs. The Arithmetic and the Logical Shifters additionally can be changed by the Barrel Shifter Because with the rotation of the data it also supply the utility the data right, left changeall mathemetically or logically.A purpose of this paper is to design the CMOS 8 bit barrel shifter using universal gates with the help of CMOS logic and the most important 2:1 multiplexers (MUX). CMOS based 8 bit barrel shifter has implemented in this paper and compared in terms of delay and power using 90 nm and 45nm technologies.

Key Words: CMOS, Low Power, Delay,Barrel Shifter, PMOS, NMOS, Cadence.

1. Introduction

In RISC processor ALU plays math and intellectual operations. Number crunching operations operate enlargement, subtraction, addition and division such as sensible operations incorporates AND, OR, NOT, NAND, NOR, XNOR and XOR. RISC processor consist ofnotice in credentials used to keep the operand in store path. The point of control unit is to give a control flag that controls the operation of the processor which tells the small scale building design which operation is done after then the time Barrel shifter is a significant element among rise operation. In augmentation operation, fractional items stimulated and protected with the aid of barrel shifters [1].Basically,have four type of shifter i.e. dependable, math, barrel and channel shifters. A barrel shifter is a combinational reason avert on the way to pass the substance of a transport determined wide variety of positions left or right by using a word. This is an essential capability in PCs and numerous sign getting ready ICs. Regularly, while transferring to one aspect, the positions cleared can be loaded with traits from the left, or if no characteristics are available, then loaded with 0in additionthe no traits are usable, the emptied positionmay be filled the evaluation of MSB [2]. A few shifters without a doubt turn the substance of a delivery filling the LSBs with the beyond substance of the MSBs for a shift left and the opposite manner around for a shift right. The logical shifter, shift the bit in left or right path; the empty spots are filled via 0. Mathematical shifter the method for left shift is identical as reasonable on the otherside right shift the clearmark is filled of sign bit. Barrel shifter includes out the rotation of bits in left or right direction; on this the empty

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© 2018 IJRAR December 2018, Volume 5, Issue 04 www.ijrar.org (E-ISSN 2348-1269, P- ISSN 2349-5138) place is stuffed by means of the bit shifted. Funnel Shifter is combination of all shifters and rotator [3]. In this paper barrel shifter is designed using multiplexer and implemented using CMOS logic. The MUX is used to universal gates which is reduce the time consumption and poer dissipation.

Barrier shifter is additional circuit that have n data inputs and n data outputs by control inputs which is allotted the shifting input data through output and bit barrel shifter known for n, n bit multiplexers. Excluding n-bit barrel shifter wants n numbers of n-bit multiplexers.If n is increased the circuit complexity also increases i.e., circuit over head, it leads to occupy more area and high power consumption and also shows the effect on speed of the operation [4].The equipment is using in various digital and analog logic circuits mutually with CMOS sensor, data converters and especiallyintegrated transceivers for lots of styles of features [5]. The result comprises the evaluation among different methodologies to reduce the Power intake in ALU design [6]. Barrel Shifter is likewise called Rotator because it rotates the statistics in a cycle so that the empty spots are filled the bits shifted off the other side. A funnel shifter can do all six sorts of shifts which can be carried out by means of previously noted shifters. The Level shifters is used toalter logical signal from one voltage to further voltage. Separately from this stage shifters are used on the pad ring and center of chip interface where low voltage signal from chip center are shifted to high voltage [7].

2. Function of Barrel Shifter

Barrel Shifter is logic circuit with ‘n’ numbers of data inputs and ‘n’ numbers of data outputs that are used to carry out transferring and rotation operation. It is operated with the help of clock. Barrel shifter is intended using multiplexers. In this research paper 2:1 MUX is use for designing the barrel shifter. This research paper contain 8-bit barrel shifter that may rotate the data in both direction. Threeselection lines s1, s2, s3 are used for rotating the data.The data comes from D flip flops are fed to the barrelshifter and using the selection line, the data is shifted.By selecting 001 it sends the data to the right shiftingoperation block. When we select 111 then data goes toleft shifting block. While sending the data to rightshifting block the left shifting block gets disabled anddata does not go to left shifting block. The same thing is done for left shifting block, while sending the data to theleft shifting block, right shifting block gets disabled anddata does not go to the rightshiftchunk. The obstructfigure of barrel shifter is given below fig.1toelucidateevery the function.If, barrel shifter can bemeasured by 2:1 MUX theninclude 8 bit barrel shifter.

Fig.1 Block Diagram of Barrel Shifter

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The fig.2 shows the multiplexer execution of 2x2 barrel shifter that is acting a left rotation of bit if we offer i0 i0 i1 i1 as enter then the output produced is in the series i1 i1 i0 i0.Input collection is shifted by bit to the left and LSB is filled by means of the shifted bits. Thus the rotation of two bits from left side is completed. The barrel shifter is toomoderatetiny. [8]. Barrel Shifter consists of an array of transistors, in which the wide variety of rows equals the word duration of the information, and the variety of columns equalsthe maximum shift width. The control wires are routed crosswise during the array. The layout of the barrel shifter is sort of symmetric and may be executed using recurring combinational logicblocks. 2:1 multiplexer can well used to layout n bit barrel shifter. Fig. Suggests the block representation of a 2X2 barrel shifter using 4, 2:1 multiplexers. If each multiplexer block is optimized for strength dissipation then the simulation time of the complete barrel shifter is reduced by means of a issue of nlog2n periodsincemodel of one multiplexer is adequate to calculating the whole energy dissipation and delay.[9]

Fig.2 MUX based of 2x2 barrel shifter

Today’s integrated circuits have a growing need for speed, area, and power. Although have many benefits, CMOS suffers from improved data, extra energy dissipation and equally improved capacitance and delay, as the logic gates grow to elevateddensity. The share circuits exploit the punycriticize devices and furtherdragdownward devices. They diminish the input capacitance and as a result develop logical attempt with the aid of doing away with huge PMOS transistors loading the inputs, however rely upon the correct ratio of pull-up to pull-down strength [10]. The 2:1 multiplexer preservefruitfully used to draw n bit Barrel shifter, stipulationequally multiplexer block is condense for forcedissipation [11].

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Fig.3 Basic block diagram of 2: 1 multiplexer

There are presented the various operations which implement using barrel shifter.In rotate operation the data can be rotated either in right or left direction.For example 1111100001 after rotating right by means of manner of one bit data is shifted in right direction via one bit and the output is 1111110000.Also if rotate the identical data in right direction by the usage of 6 bit then the output acquire is 1000011111. In 2nd example 1111100000 it's miles shifted to right by means of one bit 0111110000 while the identical data shifted right via six bit which offers the output 0000001111.Likewise for the following input 0011111110the shift of data is proven in left course, first off the input is shifted in left direction through one bit the output is 0111111100, in left shift the shifted data is removed and empty spaces are changed through zeros. In rotating data left the input is 1011111110, first off the data is circled with the aid of one bit output is 0111111101, secondly the data is rotate of two bit production is 1111111010,thenconcluding the data is revolvenearly six bit output is 1110101111

Fig.4 Shift and rotate operation in Barrel Shifter

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3. Design Implementation of Barrel Shifter

The barrel shifter is commonlyimplement as :‐

Rotate and Shift Direction:‐ The direction of rotating and shift operation is carried out with the aid of reversing the input and output vector, the usage of this technique lets in for the shift or rotate common sense to be kept simple. [A] Logical Shift Operation: ‐The logical shift operation insert zero values for both shift operation. The input vector is shifted within the select direction by number of bits in the select indication. [B] Rotate Operation: The rotating operation is change the bit out of vector MSB is inserted to LSB. [C] Shift and Rotate Operation:- We definite A to be the input operand, B to be the rotate amount, and Y to be the rotating end result. We outline A to be n bit fee, where n is an integer energy of two. Thus, B is a log2 (n) bit integer instead of values from zero to n ‐ 1 .We demonstrate A to be the input operand, B to be the shift total, and Y to be the shifted end result.We characterize A, is nbitvalue, wherever n is an integer of 2 influence.Subsequently, B is a log2(n)‐bit integer on favour of0 to ‐1 values.

Fig.5 Block Diagram of Bit Shift Rotate Operation

The rotating shift equally to the left or right. It method whilst the bits are shifted data vector on one aspect, they may be shifted to the data vector on the alternative aspect. The positions of the bits can vary their positions because the bits are routing from input to the output [12]. A rotateoperation ismoveas the bit is shifted to vector MSB and LSB.

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Fig.6 Right/Left rotates and shift operation

4. Shifting operation of Barrel Shifter Shifting operation of barrel shifter enclosecategories are right shift and left shift. The right and left identify the course of the shifting. The shift operation inserts zero values for each shift operation. The input vector is shifted in the select direction consistent with the wide variety of bits in the choose indication.

Fig.7 Right shift operation

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Fig.8 Right/Left shift operation

5. Proposed 8-bit Barrel Shifter Barrel Shifter includes an array of transistors, in which the wide variety of rows equals the phrase length of the data, and the wide variety of columns equals the maximum shift width. Proposed eight bit barrel shifter using 2:1 MUX and regularly occurring NAND gate is designed. 90 transistors (NMOS and PMOS) is make use for design8 bit Barrel Shifter, Schematic of 8 bit Barrel Shifter is shown in Fig.9 and Transient response is shown in Fig 10.

6. Analysis and Simulated Results

Fig.9 Schematic of 8-bit Barrel Shifter

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(a)

(b)

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7. PERFORMANCE PARAMETER

A. Power Dissipation in CMOS technology

Power loss on bus can be caused by three sources: 1. Leakage current occurs through the n-p junction diode, which is shown in figure1. 2. Short-circuit takes place when there is a another path going to ground. 3. Charge and discharge of freeloading capacitance acquirestate. Leakage Component of power dissipation can be shown by Figure1, which is drain to resources leakage current is independent of the drain to source voltage VDS . The reduction in the losses gives better result to system.

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Fig.11 Power dissipation in CMOS Technology

8-Bit Barrel Shifter 4 3.5 3.5 3 2.5 8-Bit Barrel Shifter at 2 1.8 90nm 1.5 8-Bit Barrel Shifter at 1 45nm 0.5 0 Power Dissipation

Fig.12 Comparison Graph of Power Dissipation

Power Analysis in the 8-bit Barrel Shifter either the transistors are in off mode or in on mode due to the early switching of opposite level for the 90 nm and 45nm technologies are shown in above fig.12.

B. Propagation Delay Proposed 8-bit Barrel Shifter is used in place of Arithmetic and the Logical Shifters and reduce delay as well as power consumption. Therefore a Proposed 8-bit Barrel Shifter can be designed to switch faster than Arithmetic and the Logical Shifters leading to a reduction in delay. The time in use for a 8-bit Barrel Shifter logic gate output to change after one or more inputs have changed is known as propagation delay. The disseminationhindrance of 8-bit barrel Shifter at 90nm and 45nm are given in Fig 13. The Delay of the through during a signal transition is given as:

퐷푒푙푎푦 = 0.69푅푒푞 × 퐶퐿

Where in equationis the 푅푒푞 resistance that is implemented using the feed through cell and 퐶퐿is the load capacitance.

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8-Bit Barrel Shifter 103 102 102 101 8-Bit Barrel Shifter at 100 90nm 99 98 8-Bit Barrel Shifter at 98 45nm 97 96 Delay

Fig.13 Comparison Graph of Delay

Result Analysis of 8-bit Barrel Shifteris shown below table 1.

Table 1 Simulated Result Summary Performance Parameter 8-Bit Barrel Shifter Technology Used 90nm 45nm Supply Voltage 0.7V 0.7V Delay 102ns 98ns Power Dissipation 3.5µW 1.8µW Transistor count 90 90

Conclusion The proposed 8 bit barrel shifter does not have much delay time as well as takes very less power. There is no need of shifting data left or right individually. This combines all features together and runs the system without any error. Also, there can be a plan to investigate special purpose applications for which one may get even more savings using proposed 8 bit barrel shifter in terms of Delay and Power. The purpose of this paper is to design the CMOS 8 bit barrel shifter using universal gates with the help of CMOS logic and the most important 2:1 multiplexers (MUX). The barrel shifters are habituallyexploit the surrounded digital signal processors and familiargatheringmainframe to direct data. CMOS based 8 bit barrel shifter has implemented in this paper and compared in terms of delay and power using 90 nm and 45nm technologies.

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References

[1]. RenukaVerma, Rajesh Mehra, “Area Efficient Layout Design AnalysisOf CMOS Barrel Shifter,” International Journal of Scientific Research Engineering & Technology (IJSRET), pp. 84-89, March 2015. [2]. A Sharma, Rajesh Mehra, “Area and Power Efficient CMOS Adder Design By Hybridizing PTL and GDI Technique,” International Journal of Computer Applications, Vol.66, No.4, pp.15-22, March 2013. [3]. Shilpa Thakur, Rajesh Mehra, “CMOS Design and Single Supply Level Shifter Using 90nm Technology,” Conference on Advances in Communication and Control Systems, pp.150-153, 2013. [4] D A Tatajee, K Rajesh.”Semi customImplementation of Area Efficient Barrel shifter”,International Journal of Advanced Computing,Engineering and Application, Vol. 1, pp.112-114, December 2012. [5] Pooja Singh, Rajesh Mehra, “Design Analysis ofXOR Gates Using CMOS & Pass Transistor”International Journal of Engineering Science InventionResearch & Development, Vol. 1 Issue 1, pp.21-25, July 2014. [6] Dhananjay Jadhav, Mithilesh Muley, Manglesh Ashtankar, “Vlsi Design of Barrel Shifter Using Complementary and Pseudo Nmos Logic”, 4th IRF International Conference, pp.170-172, March 2014. [7] Shilpa Thakur, Rajesh Mehra “CMOS Design and Single Supply Level Shifter Using 90nm Technology” Conference on Advances in Communication and Control Systems, pp.150-153, 2013. [8] Sabyasachi Das, Sunil P. Khatri.”Timing-Driven Decomposition of a Fast Barrel Shifter” IEEE, pp.574- 577, 2007. [9] Prasad D Khandekar, Dr. Mrs. Shaila Subbaraman, Venkat Raman Vinjamoori, “Quasi-Adiabatic 2X2 Barrel Shifter” Fourth International Conference on Industrial and Information Systems, ICIIS, IEEE, pp.321- 324, December 2009. [10] Akhilesh Verma, Rajesh Mehra, “Design and Analysis of Conventional and Ratioed Cmos Logic Circuit” IOSR Journal of VLSI and Signal Processing Vol.2, pp. 25-29, April 2013. [11] Prasad D Khandekar, Dr. Mrs. Shaila Subbaraman, “Low Power 2:1 MUX for Barrel Shifter” First International Conference on Emerging Trends in Engineering and Technology, IEEE, pp.404-407, July 2008. [12] Wayne Wolf, “Modern VLSI Design (System on chip Design)”, Pearson Education, pp. 319-321.

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