4 Bit Ripple Adder Verilog Free From Stuck#
4 Bit Ripple Adder Verilog Full Adders In#

4 Bit Ripple Adder Verilog Full Adders In

Adders are most widely used in applications like multipliers, DSP (i.e., FFT, FIR, and IIR). Use inputs cin and cout to indicate carry-in and carry-out.Addition usually affects the overall performance of digital systems and an arithmetic function. Use a one bit output overflow to indicate overflow in the addition. Use 2's complement to represent the numbers. Following restrictions apply: All the numbers are signed 4 bit numbers. Design a 4-bit carry-ripple adder using 4 one-bit full adders in VHDL/Verilog.

Also, the designs are analyzed for the stuck at faults (s-a-0, s-a-1) using Synopsis TetraMAX. In this work we have done comparative analysis of different types of adders in Synopsis Design Compiler using different standard cell libraries at 32/28вЂ‰nm. We have derived architectures for carry-select adder (CSA), Common Boolean Logic (CBL) based adders, ripple carry adder (RCA), and Carry Look-Ahead Adder (CLA) for 8-, 16-, 32-, and 64-bit length. Various techniques have been proposed to design fast adders.

Carry-select adders (CSA) are one of the fastest adders among traditional adders, but they are not power and area efficient. Ripple carry adders (RCA) are area and power efficient, but with drawback of being slow. We look for an area and power efficient fast adders to increase system performance. > Verilog code for BCD Adder.In any processing unit, adders are basic building block. > Verilog code for CLA (carry look ahead affer) > Verilog code for RCA (Ripple carry adder) > Verilog code for 32 Bit Pipelined Floating Point Adder.

Section 3 presents logic for CBL adder design. Section 2 deals with the analysis of adder using different topologies. The 1-bit carry-in input port C in is used to read in a carry bit , if another instance of the ripple carry adder is cascaded towards lesser significant stage.The organization of this paper is as follows. A and B are the two 4-bit input ports which is used to read in the two 4-bit numbers that are to be summed up. Carry Look-Ahead Adder (CLA) is among the fastest adders with area overhead.Following is the Verilog code for the 4-bit ripple-carry adder: // fpga4student.com: FPGA projects, Verilog projects, VHDL projects // Verilog project: Verilog code for 4-bit ripple-carry adder module rippeadder ( X, Y, S, Co) input 3:0 X, Y // Two 4-bit inputs output 3:0 S output Co Figure 2 shows the Verilog module of a 4-bit carry ripple adder.

Different Topologies for AdderThe 4-bit sum generated by the adder is presented in the 4-bit output port Sum and 1-bit carry-out in the Cout output port. Section 5 gives the conclusion followed by the references. The fault testing concept (s-a-0, s-a-1) for various adders is also discussed.

Figure 2(b) shows 64-bit adder based on CLA blocks. (b) Block diagram for 64-bit CLA based adder.Since circuit of CLA Adder for higher order bit is complex to implement directly, we have realized it by cascading 4-bit CLA blocks. Delay of -bit RCA adder is where is input setup time (for generating XOR and AND of basic inputs), is the delay of two gates, that is, AND gate and OR gates, and is the delay of the XOR gate.(a) Block diagram for 4-bit CLA. Delay is due to the rippling of carry since the consequent blocks of adder have to wait for the carry generated from the previous adder. Block diagram for 4-bit RCA is shown in Figure 1(a). Ripple Carry Adder (RCA)It is basic parallel adder where a chain of adders is cascaded with carry rippled from one stage to another.

For adding two 4-bit numbers using CSA, we require two 4-bit full adders and that can be ripple carry adder (RCA) or Carry Look-Ahead Adder (CLA). The block diagram for 4-bit addition using CSA is given in Figure 3(a). Carry-Select Adder (CSA)The carry-select adder consists of two ripple carry adders and a set of multiplexers. It has been implemented just for study purpose. This is not a pure 64-bit adder. The carry generated from any block is rippled to its successor block.

(c) Block diagram for 64-bit CLA-CSA.Figure 3(b) shows block diagram of 64-bit CSA. (b) Block diagram for 64-bit RCA-CSA. The number of bits in each CSA block is uniform.(a) Block diagram for 4-bit CSA. It means we need 16 stages of CSA to create 64-bit CSA adder. For designing 64-bit adder, we can cascade the structure shown in Figure 3(a). After the two results are available, the correct sum and carry-out are then decided by the multiplexer once the correct carry is known.

The only difference will be that the RCA block will be replaced by the CLA blocks. The more the number of multiplexers in the circuit, the more the area and power dissipation.A CLA-CSA can be designed in the same fashion. The RCA block can be of any bit not necessarily of 4 bits and the number of adders in each RCA block controls the speed and power dissipation. The bunch of MUX can be seen at the end of both blocks these control the sum. Depending upon the carry the sum is also considered to be taken. All blocks other than RCA0 are in pair whose is connected to logic 0 or 1 which acts as and the results of whom block is to be considered depend upon the carry propagating from the previous block which is controlled by the MUX which can be seen after every pair of blocks (smaller).

In the modified SQRT-CSA, the block of CSA with is replaced with BEC (Binary to Excess Converter). We have an adder with block sizes of 2, 2, 3, 4, and 5, respectively. We have five stages of CSA with different inputs bits to each stage. The block diagram for the same is given in Figure 4(a). Square-Root Carry-Select Adder (SQRT-CSA)A 16-bit CSA with variable size is created by cascading four CSA with variable input size.

If the carry propagating from previous adder ( ) is вЂњ0вЂќ then the sum ( ) will be otherwise would be. The carry which will propagate will decide the final sum and the carry for the next logic cell. (b) 64-bit Common Boolean Logic based adder.From Figure 5(a), it can be seen that MUX decides the final sum depending upon the carry propagating from previous logic cell.

Comparative Analysis of Different Adder ArchitectureIn this section, we have presented the comparison of delay, power, and area of various adders using 32/28вЂ‰nm digital standard cell library using Synopsis Design Compiler. There are 4 blocks, having 16 blocks each, which means 64 blocks of Common Boolean Logic. Delay of -bit CBL adder is where is as defined earlier, is the delay of a 2 Г— 1 MUX, and is the delay of the XOR gate.Figure 5(b) shows the block diagram of 64-bit Common Boolean Logic based adder.

In Design Compiler we need. The libraries are in three formats. Different standard cells libraries are provided by the Synopsis for the educational purpose. Important aspects of any digital circuit like area, power, delay, and so forth can be calculated by Design Compiler just providing the HDL code of the design and digital standard cells library of the technology on which you want to work.

Required Test Patterns to Test Various Adder CircuitsIn the analysis of digital circuits, testing plays a very important role. Operating frequency is 500вЂ‰MHz.Leakage power of various adders. Leakage power is considered for VвЂ‰DC at room temperature as per the data sheet. The area, delay, Dynamic Power Dissipation, and leakage are given in Table 2. Area-Delay Estimation of Basic Circuit Using Design CompilerWe have considered 2 input AND, OR, and XOR gates.

The hardware which will need lesser input test patterns to test will be better as per the testing point of view.Similarly, to find the stuck at faults we need some input patterns. As in the environment of such huge competition where the manufacture wants to launch the product as soon as possible, it requires lesser number of input test patterns. Some of the methods like ATPG are discussed in to save the time. Then different methods were introduced to minimize the number of the input test patterns. As the size of the digital design increases the number of the input patterns increases. If all the results used to be fine then we used to declare the hardware good only.

4 Bit Ripple Adder Verilog Free From Stuck

For example for 8-bit RCA we will need only 6 patterns to declare the hardware good while there can be total of 65536 input patters to add two 8-bit values. These patterns can be used to test the circuit for various stuck at faults after manufacturing.Figure 15 shows number of input test patterns required to test various adders for 8, 16, 32, and 64 bits. Input test patterns using ATPG for different digital circuits are generated by TetraMAX and details are given in Figure 15. While such techniques may impede other ATPG tools, TetraMAX is able to obtain coverage on the resulting complex logic. With TetraMAX, designers can generate high-quality manufacturing test patterns without compromising on high performance design techniques. If all the outputs corresponding to all the inputs are correct we can say that the hardware is free from stuck at faults.TetraMAX is used to generate pattern using ATPG for different circuits.

For 8-bit adders RCA-CSA is approximately 3% faster than SQRT-CSA and CLA-CSA, 42% faster than RCA and CSA-CBL, and 60% faster than CLA.For 16-bit adders RCA-CSA is approximately 2% faster than SQRT-CSA and CLA-CSA, 90% faster than CSA-CBL and RCA, and 125% faster than CLA.For 32-bit adders SQRT-CSA is approximately 14% faster than RCA-CSA and CLA-CSA, 170% faster than CSA-CBL and RCA, and 210% faster than CLA. Test generation analysis on the adders was also performed.With Respect to Delay. The parameters of comparison were delay, area, and power (dynamic and leakage) using digital standard cell library.