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up-down counter with delay

create_clock -period 10.000 -name sys_clk_pin -waveform {0.000 4.000} -add [get_ports clk] Verilog code module Counter_UP_down(led, clk, sw, btn); output [3:0] led; input [1:0] sw; input [3:0] btn; input clk; reg [3:0] led; reg [26:0] count; reg clkdiv; initial begin     count = 0;     clkdiv = 0; end always @ (posedge clk) begin     if (btn[3])     begin         //count speed = high         count <= count + 1;         if(count == 12500000)         begin             count <= 0;             clkdiv <= ~clkdiv;         end     end       else         begin           //count speed = low           count <= count + 1;         ...
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Verilog-'timescale

System tasks $time and $realtime are used to return  current simulation time. 'timescale <time unit> <time precision> Examples 'timescale   1ns/1ps 'timescale 10ns/1ns 'timescale 1ns/1ns Example-1 / Declare the timescale where time_unit is 1ns // and time_precision is 1ps `timescale 1ns / 1ps   // NOTE: Testbench is the same as in previous example module top ; // To understand the effect of timescale, let us // drive a signal with some values after some delay reg data ;   initial begin // Initialize the signal to 0 at time 0 units data <= 0 ;   // Advance by 1 time unit, display a message and toggle val # 1 $display ( "Time=%0t At time #1" , $realtime ) ; data <= 1 ;   // Advance by 0.49 time unit and toggle val # 0.49 $display ( "Time=%0t At time #0.49" , $realtime ) ; data <= 0 ;   // Advance by 0.50 time unit and toggle val # 0.50 ...
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Part-3 Example of Sequential Circuits

Example-1 A 4-Bit Shift register with asynchronous load. module bit4_SHreg(R,L,w,clk,Q);     input [3:0]R;     input L,w,clk;     output reg [3:0]Q; always@(posedge L,posedge clk) //begin if (L) Q<=R; else begin Q[0]<=Q[1]; Q[1]<=Q[2]; Q[2]<=Q[3]; Q[3]<=w;            /// w is data input                            /// w-> Q3 -> Q2-> Q1->Q0 end endmodule Test Bench module test_bit4SHreg; reg [3:0]R;    reg L,w,clk;   wire [3:0]Q;       bit4_SHreg r0(R,L,w,clk,Q);         initial begin clk=0; L=0;w=0;R=0; $monitor("R=%d,w=%b,Q=%b",R,w,Q); end always #5 clk=~clk; initial begin #1 L=1; R=6; #7 L=0; w=1; #8 w=0;  #9 w=1; #9 w=0; #9 w=1; #9 L=1; R=5; #3 R=4; #5 R=7; end    endmodule Simulation Results ...
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Part-2 Verilog Examples for Sequential circuits

Find MATlAB Programs for signals and systems with output here↓  https://meenakshiagarwalvlsi.blogspot.com/p/graphical-representation-of-time.html Example-1 Verilog code for an arbitrary size register // N-bit register with Asynchronous reset module n_bitreg(D,clk,clr,Q);     parameter n=16;     input [n-1:0]D;     input clk,clr;     output reg[n-1:0] Q;       always@(negedge clr, posedge clk)     begin     if(!clr)     ///asynchronous clear active low     Q<=0;     else     Q<=D;     end endmodule //Test Bench module test_regNbit; parameter n=16;  reg [n-1:0]D; reg clk,clr; wire [n-1:0]Q; n_bitreg r1(D,clk,clr,Q); initial begin clk=0; clr=0;D=0; $monitor("D=%d,Q=%d",D,Q); end always #5 clk=~clk; initial begin #1 clr=1; D=8; #5 clr=0; D=7; #8 clr=1; D=12; #5 D=1...
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Part-1 Verilog Examples for Sequential circuits

Find MATlAB Programs for signals and systems with output here↓  https://meenakshiagarwalvlsi.blogspot.com/p/graphical-representation-of-time.html Counters with synchronous and asynchronous reset Example-1 Verilog code for an n-bit Up-counter with enable (en), load (l) and asynchronous reset with test bench. module upcount(r,rst,clk,en,l,Q); parameter n=16; input [n-1:0]r; input rst,clk,en,l; output reg [n-1:0]Q; always@(negedge rst, posedge clk)  // asynchronous clear, posedge triggered clock a begin if(!rst) Q<=0; else if (l)  // synchronous load from R Q<=r; else if(en)      //counts up if en=1 Q<=Q+1; end endmodule Test Bench with a clock of time period 10 time units module test_upcount; parameter n=16; reg [n-1:0]r; reg rst,clk,en,l; wire [n-1:0]Q; upcount t0(r,rst,clk,en,l,Q); initial begin clk=0; l=0;en=0;rst=0;r=0; $monitor("r=%b,en=%b,l=%b,Q=%d \n",r,en,l,Q); end always #5 clk=~clk; initial begi...
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Various examples of RTL design have been given as follows: Example 1  : Verilog code for a 4-bit gray to binary converter using structure modelling. module gray2bin( input [3:0] G, output [3:0] B ); assign B[3]=G[3]; xor x1(B[2],B[3],G[2]); xor x2(B[1],B[2],G[1]); xor x3(B[0],B[1],G[0]); endmodule Test bench `timescale 1ns / 1ps module gray_binT; reg [3:0] G1;    wire [3:0] B1;    gray2bin g1(G1,B1);    initial     begin    $monitor("Gray code values=%b, Binary Values=%b",G1,B1);    //$monitor("Binary values of grey codes=%b",B1);    end    initial    begin    G1=4'd0;    #6 G1=4'b0001;    #4G1=4'd2;    #6 G1=4'd3;    #6 G1=4'd4;       #4G1=4'd5;       #6 G1=4'd6;       #6 G1=4'd7;    ...
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VERILOG HDL: Vectors and arrays

Vectors:  Nets or reg data types in verilog HDL can be declared as vectors (a word of multiple bits). wire a;      // single bit variable. wire [4:0]b;  //5-bit vector wire reg clock;     // scalar register reg [0:31] bus;  // 32-bits bus register reg [63:0]count1;  // 64-bit register count1 reg [0:31]count2;   // 32-bit register count2 Part select of a variable vector bus[31]=1'b0;   // set 31th bit of bus count1[0]; // 0th bit of count1 register count1[31-:8] ;  //// start bit=31, width=8=> data[31:24] count1[24+:8] ;  //// start bit=24, width=8=> data[31:24] count2[31-:8] ;  //// start bit=31, width=8=> data[24:31] count2[24+:8] ;  //// start bit=24, width=8=> data[24:31] //in a loop to select all bytes of the vector. input a,b; reg j; reg [255:0]data1; reg [0:255]data2; alsways@ (a,b) begin for (j=0; j<=31; j=j+1) byte = data1[(j*8)+:8]; //Sequenc...
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