Mixed Signal Circuit Design and Simulation Marathon

XOR-XNOR-Gate

• Abstract
• Reference Circuit Diagram
• Reference Waveform
• Circuit Details
• Truth Table
• Software Used
  • eSim
  • NgSpice
  • Makerchip
  • Verilator
• Circuit Diagram in eSim
• Verilog Code
• Makerchip
• Makerchip Plots
• Netlists
• NgSpice Plots
• GAW Plots
• Steps to run generate NgVeri Model
• Steps to run this project
• Acknowlegdements
• References

Table of contents generated with markdown-toc

Abstract

With the increasing technology, the size of the transistors is reducing. The reducing size leads to the tradeoff between power, efficiency and switching time. Because of which there is requirement to design low power transistor with less area and lesser number of gates. The design should use lesser power as well. Thus, making it more and more efficient.

Reference Circuit Diagram

Reference Waveform

Circuit Details

As shown in the figure we have two cross coupled circuits of PMOS logic and NMOS logic.
On the PMOS logic we are getting the output as XOR while in the NMOS block we get the output as XNOR.
The transistors M4 and M3 behave as a pass transistor and pass the output of M1, M2 and M5, M6 respectively.

The advantage of the above circuit is that it uses only 6 transistors and gives both outputs of XOR and XNOR while the general circuit uses 8 transistors with only one output either XOR or XNOR.
This way it consumes less space and less power and is efficient in many ways.

Truth Table

Input A	Input B	Output XOR	Output XNOR
0	0	0	1
0	1	1	0
1	0	1	0
1	1	0	1

Software Used

eSim

It is an Open Source EDA developed by FOSSEE, IIT Bombay. It is used for electronic circuit simulation. It is made by the combination of two software namely NgSpice and KiCAD.
For more details refer:
https://esim.fossee.in/home

NgSpice

It is an Open Source Software for Spice Simulations. For more details refer:
http://ngspice.sourceforge.net/docs.html

Makerchip

It is an Online Web Browser IDE for Verilog/System-verilog/TL-Verilog Simulation. Refer
https://www.makerchip.com/

Verilator

It is a tool which converts Verilog code to C++ objects. Refer: https://www.veripool.org/verilator/

Circuit Diagram in eSim

The following is the schematic in eSim:

Verilog Code

Makerchip

\TLV_version 1d: tl-x.org
\SV
/* verilator lint_off UNUSED*/  /* verilator lint_off DECLFILENAME*/  /* verilator lint_off BLKSEQ*/  /* verilator lint_off WIDTH*/  /* verilator lint_off SELRANGE*/  /* verilator lint_off PINCONNECTEMPTY*/  /* verilator lint_off DEFPARAM*/  /* verilator lint_off IMPLICIT*/  /* verilator lint_off COMBDLY*/  /* verilator lint_off SYNCASYNCNET*/  /* verilator lint_off UNOPTFLAT */  /* verilator lint_off UNSIGNED*/  /* verilator lint_off CASEINCOMPLETE*/  /* verilator lint_off UNDRIVEN*/  /* verilator lint_off VARHIDDEN*/  /* verilator lint_off CASEX*/  /* verilator lint_off CASEOVERLAP*/  /* verilator lint_off PINMISSING*/    /* verilator lint_off BLKANDNBLK*/  /* verilator lint_off MULTIDRIVEN*/     /* verilator lint_off WIDTHCONCAT*/  /* verilator lint_off ASSIGNDLY*/  /* verilator lint_off MODDUP*/  /* verilator lint_off STMTDLY*/  /* verilator lint_off LITENDIAN*/  /* verilator lint_off INITIALDLY*/    

//Your Verilog/System Verilog Code Starts Here:
module ixorxnor(output yXOR,output yXNOR, input a,input b);
  


  assign yXOR = a ^ b;
  assign yXNOR = ~(a ^ b);
  
endmodule 

//Top Module Code Starts here:
	module top(input logic clk, input logic reset, input logic [31:0] cyc_cnt, output logic passed, output logic failed);
		logic  yXOR;//output
		logic  yXNOR;//output
		logic  a;//input
		logic  b;//input
//The $random() can be replaced if user wants to assign values
      always @(posedge clk) 
         begin
         a = $random();
		   b = $random();
            end
		ixorxnor ixorxnor(.yXOR(yXOR), .yXNOR(yXNOR), .a(a), .b(b));
	
\TLV
//Add \TLV here if desired                                     
\SV
endmodule

Makerchip Plots

Netlists

NgSpice Plots

GAW Plots

Steps to run generate NgVeri Model

1. Open eSim
2. Run NgVeri-Makerchip
3. Add top level verilog file in Makerchip Tab
4. Click on NgVeri tab
5. Add dependency files
6. Click on Run Verilog to NgSpice Converter
7. Debug if any errors
8. Model created successfully

Steps to run this project

1. Open a new terminal
2. Clone this project using the following command:
   git clone https://github.com/Eyantra698Sumanto/XOR-XNOR-Gate.git
   
3. Change directory:
   cd eSim_project_files/xor_xnor
   
4. Run ngspice:
   ngspice xor_xnor.cir.out
   
5. To run the project in eSim:

• Run eSim
  
• Load the project
  
• Open eeSchema
  

Acknowlegdements

1. FOSSEE, IIT Bombay
2. Steve Hoover, Founder, Redwood EDA
3. Kunal Ghosh, Co-founder, VSD Corp. Pvt. Ltd. - kunalpghosh@gmail.com
4. Sumanto Kar, eSim Team, FOSSEE

References

1. Ahmad, Nabihah & Hasan, Rezaul. (2011). A new design of XOR-XNOR gates for low power application. 10.1109/ICEDSA.2011.5959039.
2. K. Ravali, N. R. Vijay, S. Jaggavarapu and R. Sakthivel, "Low power XOR gate design and its applications," 2017 Fourth International Conference on Signal Processing, Communication and Networking (ICSCN), 2017, pp. 1-4, doi: 10.1109/ICSCN.2017.8085699.
3. https://github.com/Eyantra698Sumanto/Two-in-One-Low-power-XOR-XNOR-Gate.git