What is Carry Save Adder?
A Carry Save Adder (CSA) is a type of digital circuit that performs fast, parallel addition of multiple binary numbers. It is also known as a Ripple-Carry Adder (RCA) because the carry from one bit position to the next "ripples" through the entire adder. The circuit diagram for a CSA typically includes multiple full adders, which are connected in a specific way to allow for parallel addition. The verilog code for a CSA will depend on the specific design of the circuit, but it will typically include code for the full adders as well as logic for the carry-in and carry-out bits.
A Carry Save Adder circuit is typically composed of multiple full adder circuits connected in a specific way to allow for parallel addition. A full adder circuit typically includes three inputs (A, B, and Cin) and two outputs (Sum and Cout). In a Carry Save Adder, the full adders are connected such that the A and B inputs of each full adder are connected to the corresponding bit positions of the numbers being added, and the Cin input of each full adder is connected to the Cout output of the previous full adder. The Sum outputs of all the full adders are then combined to form the sum of the numbers being added, and the Cout outputs are combined to form the carry out.
fpga verilog code example,
Here is an example of verilog code for a 4-bit Carry Save Adder:
module CSA_4bit (A, B, Ci, S, Co); input [3:0] A, B; input Ci; output [3:0] S; output Co; wire Ci_1, Ci_2, Ci_3; full_adder FA0 (A[0], B[0], Ci, S[0], Ci_1); full_adder FA1 (A[1], B[1], Ci_1, S[1], Ci_2); full_adder FA2 (A[2], B[2], Ci_2, S[2], Ci_3); full_adder FA3 (A[3], B[3], Ci_3, S[3], Co); endmodule
Note that in this example, the full_adder module is assumed to be a standard full adder module with input ports for A, B, Cin and output ports for Sum and Cout.
It is worth mentioning that Carry Save Adder is a parallel adder and it's output is not a single sum but two separate parts, one is the sum and the other is the carry out. It is used in specific situations where the carry out is also needed and not only the sum.
