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This paper presents a technology-independent design and simulation of a modified architecture of the Carry-Save Adder. This architecture is shown to produce the result of the addition fast and by requiring a minimum number of logic gates. Binary addition is carried out by a series of XOR, AND and Shift-left operations. These operations are terminat...
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Context 1
... logic circuit of figure 7 is made of 4 registers: A and B to load the addends, C and D to store the results of XOR and AND logic operations. The registers A and B have 2-to-1 multiplexers connected at their inputs used to select either the addends A and B or to reload C and D after the XOR and AND logic operations. This logic circuit stops shifting the register D and reloading the registers A and B when the register D is equal to 0. In order to keep the logic circuit of figure 8 simple, it does not show a “zero-detector” at the output of register D ( Basically a 5-input NOR gate). The logic circuit of figure 7 was simulated with Quartus II design software. D-flip-flips with Enable signal were used to make the registers A, B, C and D. For testing purposes, a binary value of ‘1011’ was loaded into the register A, and ‘0110’ was loaded into the register B. A manual execution of the algorithm of figure 1 using these addends shows that three shift operations are needed to obtain the result. Table 5 shows the control signals used for the synchronous parallel adder. Figure 8 shows the input and output wave forms, and table 6 shows the timing and the values of the ...
Context 2
... save adder is used to compute sum of three or more n-bit binary numbers. Carry save adder is same as a full adder. Figure 1 shows the sum of two 32-bit binary numbers, so 32 full adders are used at first stage. Carry save unit consists of 32 full adders, each of which computes single sum and carry bit based only on the corresponding bits of the two input numbers Let X and Y are two 32-bit numbers and produces partial sum and carry as S and C as shown in the following example: Si = Xi xor Yi Ci = Xi and Yi The final addition is then computed as: 1. Shifting the carry sequence C left by one place. 2. Placing a 0 to the front (MSB) of the partial sum sequence S. 3. Finally, a ripple carry adder is used to add these two together and computing the resulting ...
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Citations
... Carry save adder is same as a full adder. But as shown in Fig. 4 (Alaoui, 2011), here we are computing sum of two 16-bit binary numbers, so we take 16 half adders at first stage instead of using 16 full adders. Therefore, carry save unit consists of 16 half adders, each of which computes single sum and carry bit based only on the corresponding bits of the two input numbers. ...
This study presents an architectural approach to the design of Low power and area efficient reconfigurable Finite Impulse Response (FIR) filter. FIR digital filters are used in DSP by the virtue of its, linear phase, fewer finite precision error, stability and efficient implementation. The proposed architectures implemented by using carry save adder, it offer Low power and area reductions and compared to the best existing reconfigurable FIR filter implementations in the literature and the proposed architectures have been implemented and tested on Spartan-3 xc3s200-5pq208 Field-Programmable Gate Array (FPGA) and synthesized.
... The idea of delaying carry resolution until the end, or saving carries, is due to John von Neumann. [3] If the adder is required to add two numbers and produce a result, carry-save addition is useless, since the result still has to be converted back into binary and this still means that carries have to propagate from right to left. But in large-integer arithmetic, addition is a very rare operation, and adders are mostly used to accumulate partial sums in a multiplication. ...
... But in large-integer arithmetic, addition is a very rare operation, and adders are mostly used to accumulate partial sums in a multiplication. [3] ...
... Architecture of Carry save Adder[3] ...
... The need of speed optimization in addition operation for high speed datapaths led to the development of fast adder architectures. The carry save adder [5] topology is one such fundamental fast adder design available to the digital designers. The basic principle of this architecture is to save and forward the carry bits from individual bit adder stages (of one adder chain) to the next appropriate bit adder stage (of the next adder chain) instead of rippling it across the same stage. ...
Adders form an indispensable part of digital
integrated design due to their extensive application in
efficient implementation of basic binary arithmetic. The
pre- requisites of a basic adder topology are undoubtedly
faster operating speed, acceptable power consumption
and effectively lower on chip area. The present paper
provides an in depth comparative analysis of various
contemporary adder topologies. The detailed study of the
adder architectures presented in this paper is intended to
facilitate the trade-off between area, propagation delay
and power dissipation while selecting an adder topology
for any digital design. Five different adder topologies
namely ripple carry adder, carry save adder, carry bypass
adder, linear carry select adder and square root carry
select adder are compared exhaustively on the basis of
several design metric and performance parameters in this
work using Cadence EDA tool in 45nm CMOS process
technology. The robustness of the designs is analysed
using corner analysis at various process corners.
