![Adder Adder](/uploads/1/2/5/3/125374488/216621007.jpg)
Jan 10, 2018 In the above figure, A, B 4-bit input, C0 is Carry in and S 4-bit output, C4 is Carry out. The remaining C1, C2, C3 are intermediate Carry. They are called signals in VHDL Code. To implement 4 bit Ripple Carry Adder VHDL Code, First implement VHDL Code for full adder.We Already implemented VHDL Code for Full Adder. You can, you would have to use two n-bit adders to add two sets of two numbers. Then use an n+1 bit bit adder to add those two numbers. Think of it as (a+b)+(c+d) were (a+b) and (c+d) use two n-bit adders then you use an n+1 bit adder to add the results of the first two adder s.
![8 bit adder verilog 8 bit adder verilog](/uploads/1/2/5/3/125374488/447748736.jpg)
A carry-skip adder (also known as a carry-bypass adder) is an adder implementation that improves on the delay of a ripple-carry adder with little effort compared to other adders. The improvement of the worst-case delay is achieved by using several carry-skip adders to form a block-carry-skip adder. For more information about carry bypass adder you can refer to wikipedia article.Basic structure of 4-bit Carry Skip/Bypass Adder is shown below.The Verilog Code for 16-bit Carry Skip Adder is given below.