站长百科 HDLBits答案——Verilog Language 正文

HDLBits答案——Verilog Language

2022-12-30,,,

Verilog Language

1 Basics

1.1 Wire

module top_module( input in, output out );

    assign out = in;

endmodule

1.2 Wire4

module top_module(

    input a,b,c,

    output w,x,y,z );

    assign w = a;

    assign x = b;

    assign y = b;

    assign z = c;

endmodule

1.3 Notgate

module top_module( input in, output out );

    assign out =~in;

endmodule

1.4 Andgate

module top_module(

    input a,

    input b,

    output out );

    assign out = a&b;

endmodule

1.5 Norgate

module top_module(

    input a,

    input b,

    output out );

    assign out = ~(a|b);

endmodule

1.6 Xnorgate

module top_module(

    input a,

    input b,

    output out );

    assign out = ~((~a&b)|(a&~b));

endmodule

1.7 Declaring wires

`default_nettype none

module top_module(

    input a,

    input b,

    input c,

    input d,

    output out,

    output out_n   ); 

    wire e,f;

    wire out_0;

    assign e = a&b;

    assign f = c&d;

    assign out_0 = e|f;

    assign out_n = ~out_0;

    assign out = out_0;

endmodule

1.8 7458

module top_module (

    input p1a, p1b, p1c, p1d, p1e, p1f,

    output p1y,

    input p2a, p2b, p2c, p2d,

    output p2y );

    wire a,b,c,d;

    assign a = p1c&p1b&p1a;

    assign b = p2a&p2b;

    assign c = p2c&p2d;

    assign d = p1f&p1e&p1d;

    assign p2y = b|c;

    assign p1y = a|d;

endmodule

2 Vector

2.1 Vector0

module top_module (

    input wire [2:0] vec,

    output wire [2:0] outv,

    output wire o2,

    output wire o1,

    output wire o0  ); // Module body starts after module declaration

    assign outv = vec;

    assign o2 = vec[2];

    assign o1 = vec[1];

    assign o0 = vec[0];

endmodule

2.2 Vector1

`default_nettype none     // Disable implicit nets. Reduces some types of bugs.

module top_module(

    input wire [15:0] in,

    output wire [7:0] out_hi,

    output wire [7:0] out_lo );

    assign out_hi = in[15:8];

    assign out_lo = in[7:0];

endmodule

2.3 Vector2

module top_module(

    input [31:0] in,

    output [31:0] out );//

    // assign out[31:24] = ...;

    assign out[31:24] = in[7:0];

    assign out[23:16] = in[15:8];

    assign out[15:8] = in[23:16];

    assign out[7:0] = in[31:24];

endmodule

2.4 Vectorgates

module top_module(

    input [2:0] a,

    input [2:0] b,

    output [2:0] out_or_bitwise,

    output out_or_logical,

    output [5:0] out_not

);

    assign out_or_bitwise = a|b;

    assign out_or_logical = a||b;

    assign out_not[5:3] = ~b;

    assign out_not[2:0] = ~a;

endmodule

2.5 Gates4

module top_module(

    input [3:0] in,

    output out_and,

    output out_or,

    output out_xor

);

    assign out_and = in[3]&in[2]&in[1]&in[0];

    assign out_or = in[3]|in[2]|in[1]|in[0];

    assign out_xor = in[3]^in[2]^in[1]^in[0];

endmodule

2.6 Vector3

module top_module (

    input [4:0] a, b, c, d, e, f,

    output [7:0] w, x, y, z );//

    reg[1:0] t;

initial

    begin

    t = 2'b11;

    end

    // assign { ... } = { ... };

    assign w[7:0] = {a[4:0],b[4:2]};

    assign x[7:0] = {b[1:0],c[4:0],d[4]};

    assign y[7:0] = {d[3:0],e[4:1]};

    assign z[7:0] = {e[0],f[4:0],t};

endmodule

2.7 Vectorr

module top_module(

    input [7:0] in,

    output [7:0] out

);

    assign out = {in[0],in[1],in[2],in[3],in[4],in[5],in[6],in[7]};

endmodule

2.8 Vector4

module top_module (

    input [7:0] in,

    output [31:0] out );//

    // assign out = { replicate-sign-bit , the-input };

    assign out = {{24{in[7]}},in};

endmodule

2.9 Vector5

module top_module (

    input a, b, c, d, e,

    output [24:0] out );//

    // The output is XNOR of two vectors created by

    // concatenating and replicating the five inputs.

    // assign out = ~{ ... } ^ { ... };

    assign out[24:20] = ~{5{a}}^{a,b,c,d,e};

    assign out[19:15] = ~{5{b}}^{a,b,c,d,e};

    assign out[14:10] = ~{5{c}}^{a,b,c,d,e};

    assign out[9:5] = ~{5{d}}^{a,b,c,d,e};

    assign out[4:0] = ~{5{e}}^{a,b,c,d,e};

endmodule

3 Modules:Hierarchy

3.1 Module

module top_module ( input a, input b, output out );

    mod_a U1(a,b,out);

endmodule

3.2 Module pos

module top_module (

    input a,

    input b,

    input c,

    input d,

    output out1,

    output out2

);

    mod_a U1(out1,out2,a,b,c,d);

endmodule

3.3 Module name

module top_module (

    input a,

    input b,

    input c,

    input d,

    output out1,

    output out2

);

    mod_a U1(.out1(out1),.out2(out2),.in1(a),.in2(b),.in3(c),.in4(d));

endmodule

3.4 Module shift

module top_module ( input clk, input d, output q );

    wire d1,d2;

    my_dff U1(clk,d,d1);

    my_dff U2(clk,d1,d2);

    my_dff U3(clk,d2,q);

endmodule

3.5 Module shift8

module top_module (

    input clk,

    input [7:0] d,

    input [1:0] sel,

    output [7:0] q

);

    wire [7:0] q0,q1,q2;

    my_dff8 U0(clk,d,q0);

    my_dff8 U1(clk,q0,q1);

    my_dff8 U8(clk,q1,q2);

    always @(sel)begin

        case(sel)

            2'b00:

                q = d;

            2'b01:

                q = q0;

            2'b10:

                q = q1;

            2'b11:

                q = q2;

            default:

                q = 0;

        endcase

    end

endmodule

3.6 Module add

module top_module(

    input [31:0] a,

    input [31:0] b,

    output [31:0] sum

);

    wire cout1;

    add16 U1( a[15:0], b[15:0], 0, sum[15:0], cout1 );

    add16 U2( a[31:16], b[31:16], cout1, sum[31:16], );

endmodule

3.6 Module fadd

module top_module (

    input [31:0] a,

    input [31:0] b,

    output [31:0] sum

);//

    wire cout1;

    add16 U1( a[15:0], b[15:0], 0, sum[15:0], cout1 );

    add16 U2( a[31:16], b[31:16], cout1, sum[31:16], );

endmodule

module add1 ( input a, input b, input cin,   output sum, output cout );

// Full adder module here

    assign sum = a^b^cin;

    assign cout = (a&b)|(a&cin)|(b&cin);

endmodule

3.7 Module cseladd

module top_module(

    input [31:0] a,

    input [31:0] b,

    output [31:0] sum

);

    wire cout1;

    wire [15:0] sum0,sum1,sum_l,sum_h;

    add16 U1( a[15:0], b[15:0], 0, sum_l, cout1 );

    add16 U2( a[31:16], b[31:16], 0,sum0, );

    add16 U3( a[31:16], b[31:16], 1,sum1, );

    always @(*)begin

        if(cout1)

            begin

            sum_h = sum1;

            end

        else

            begin

            sum_h = sum0;

            end

    end

    assign sum = {sum_h,sum_l};

endmodule

3.8 Module addsub

module top_module(

    input [31:0] a,

    input [31:0] b,

    input sub,

    output [31:0] sum

);

    wire cout1;

    wire [31:0] b1;

    always @(*) begin

        if(sub)

            b1 = ~b;

        else

            b1 = b;

    end

    add16 U1( a[15:0], b1[15:0], sub, sum[15:0], cout1 );

    add16 U2( a[31:16], b1[31:16], cout1, sum[31:16], );

endmodule

4 Procedures

4.1 Alwaysblock1

// synthesis verilog_input_version verilog_2001

module top_module(

    input a,

    input b,

    output wire out_assign,

    output reg out_alwaysblock

);

    assign out_assign = a&b;

    always @(*)begin

        out_alwaysblock = a&b;

    end

endmodule

4.2 Alwaysblock2

// synthesis verilog_input_version verilog_2001

module top_module(

    input clk,

    input a,

    input b,

    output wire out_assign,

    output reg out_always_comb,

    output reg out_always_ff   );

    assign out_assign = a^b;

    always @(*)begin

        out_always_comb = a^b;

    end

    always @(posedge clk)begin

        out_always_ff = a^b;

    end

endmodule

4.3 Always if

// synthesis verilog_input_version verilog_2001

module top_module(

    input a,

    input b,

    input sel_b1,

    input sel_b2,

    output wire out_assign,

    output reg out_always   );

    assign out_assign = (sel_b1&sel_b2)? b:a;

    wire [1:0] sel;

    assign sel = {sel_b1,sel_b2};

    always @(*)begin

        case(sel)

            0:out_always = a;

            1:out_always = a;

            2:out_always = a;

            3:out_always = b;

        endcase

    end

endmodule

4.4 Always if2

// synthesis verilog_input_version verilog_2001

module top_module (

    input      cpu_overheated,

    output reg shut_off_computer,

    input      arrived,

    input      gas_tank_empty,

    output reg keep_driving  ); //

    always @(*) begin

        if (cpu_overheated)

        	shut_off_computer = 1;

        else

            shut_off_computer = 0;

    end

    always @(*) begin

        if (~arrived)

            keep_driving = ~gas_tank_empty;

        else

            keep_driving = 0;

    end

endmodule

4.5 Always case

// synthesis verilog_input_version verilog_2001

module top_module (

    input [2:0] sel,

    input [3:0] data0,

    input [3:0] data1,

    input [3:0] data2,

    input [3:0] data3,

    input [3:0] data4,

    input [3:0] data5,

    output reg [3:0] out   );//

    always@(*) begin  // This is a combinational circuit

        case(sel)

            3'b000:out = data0;

            3'b001:out = data1;

            3'b010:out = data2;

            3'b011:out = data3;

            3'b100:out = data4;

            3'b101:out = data5;

            default:out = 0;

        endcase

    end

endmodule

4.6 Always case2

// synthesis verilog_input_version verilog_2001

module top_module (

    input [3:0] in,

    output reg [1:0] pos  );

    always @(*) begin

        case(in)

            4'b0000 : pos = 0;

            4'b0001 : pos = 0;

            4'b0010 : pos = 1;

            4'b0011 : pos = 0;

            4'b0100 : pos = 2;

            4'b0101 : pos = 0;

            4'b0110 : pos = 1;

            4'b0111 : pos = 0;

            4'b1000 : pos = 3;

            4'b1001 : pos = 0;

            4'b1010 : pos = 1;

            4'b1011 : pos = 0;

            4'b1100 : pos = 2;

            4'b1101 : pos = 0;

            4'b1110 : pos = 1;

            4'b1111 : pos = 0;

        endcase

    end

endmodule

4.7 Always casez

// synthesis verilog_input_version verilog_2001

module top_module (

    input [7:0] in,

    output reg [2:0] pos  );

    always @(*)begin

        casez(in)

            8'bzzzzzzz1:pos=0;

            8'bzzzzzz1z:pos=1;

            8'bzzzzz1zz:pos=2;

            8'bzzzz1zzz:pos=3;

            8'bzzz1zzzz:pos=4;

            8'bzz1zzzzz:pos=5;

            8'bz1zzzzzz:pos=6;

            8'b1zzzzzzz:pos=7;

            default:pos=0;

        endcase

    end

endmodule

4.8 Always nolatches

// synthesis verilog_input_version verilog_2001

module top_module (

    input [15:0] scancode,

    output reg left,

    output reg down,

    output reg right,

    output reg up  ); 

    always @(*)begin

        up = 1'b0; down = 1'b0; left = 1'b0; right = 1'b0;

    	case (scancode)

        	16'he06b:left = 1;

            16'he072:down = 1;

            16'he074:right = 1;

            16'he075:up = 1;

            default: ;

    	endcase

    end

endmodule

5 More Verilog Features

5.1 Conditional

module top_module (

    input [7:0] a, b, c, d,

    output [7:0] min);//

    // assign intermediate_result1 = compare? true: false;

    wire [7:0] min1,min2;

    assign min1 =(a<b)?  a: b;

    assign min2 =(min1<c)? min1: c;

    assign min =(min2<d)? min2: d;

endmodule

5.2 Reduction

module top_module (

    input [7:0] in,

    output parity);

    assign parity = ^in[7:0];

endmodule

5.3 Gates100

module top_module(

    input [99:0] in,

    output out_and,

    output out_or,

    output out_xor

);

    assign out_and = &in[99:0];

    assign out_or = |in[99:0];

    assign out_xor = ^in[99:0];

endmodule

5.4 Vector100r

module top_module(

    input [99:0] in,

    output [99:0] out

);

    integer i;

    always @(*)begin

    	for(i = 0;i<100;i++)

        	out[i] = in[99-i];

    end

endmodule

5.5 Popcount255

module top_module(

    input [254:0] in,

    output [7:0] out );

    integer i;

    always @(*)begin

        out = 0;

        for(i=0;i<255;i++)

            if(in[i]==1) out++;

        	else out = out;

    end

endmodule

5.6 Adder100i

module top_module(

    input [99:0] a, b,

    input cin,

    output [99:0] cout,

    output [99:0] sum );

    integer i;

    add8 L1(a[7:0],b[7:0],cin,sum[7:0],cout[7:0]);

    add8 L2(a[15:8],b[15:8],cout[7],sum[15:8],cout[15:8]);

    add8 L3(a[23:16],b[23:16],cout[15],sum[23:16],cout[23:16]);

    add8 L4(a[31:24],b[31:24],cout[23],sum[31:24],cout[31:24]);

    add8 L5(a[39:32],b[39:32],cout[31],sum[39:32],cout[39:32]);

    add8 L6(a[47:40],b[47:40],cout[39],sum[47:40],cout[47:40]);

    add8 L7(a[55:48],b[55:48],cout[47],sum[55:48],cout[55:48]);

    add8 L8(a[63:56],b[63:56],cout[55],sum[63:56],cout[63:56]);

    add8 L9(a[71:64],b[71:64],cout[63],sum[71:64],cout[71:64]);

    add8 L10(a[79:72],b[79:72],cout[71],sum[79:72],cout[79:72]);

    add8 L11(a[87:80],b[87:80],cout[79],sum[87:80],cout[87:80]);

    add8 L12(a[95:88],b[95:88],cout[87],sum[95:88],cout[95:88]);

    add1 P1(a[96],b[96],cout[95],sum[96],cout[96]);

    add1 P2(a[97],b[97],cout[96],sum[97],cout[97]);

    add1 P3(a[98],b[98],cout[97],sum[98],cout[98]);

    add1 P4(a[99],b[99],cout[98],sum[99],cout[99]);

endmodule

module add1 ( input a, input b, input cin,   output sum, output cout );

// Full adder module here

    assign sum = a^b^cin;

    assign cout = (a&b)|(a&cin)|(b&cin);

endmodule

module add8 ( input [7:0]a, input [7:0] b, input cin ,output [7:0] sum,output [7:0] cout);

    add1 U1(a[0],b[0],cin,sum[0],cout[0]);

    add1 U2(a[1],b[1],cout[0],sum[1],cout[1]);

    add1 U3(a[2],b[2],cout[1],sum[2],cout[2]);

    add1 U4(a[3],b[3],cout[2],sum[3],cout[3]);

    add1 U5(a[4],b[4],cout[3],sum[4],cout[4]);

    add1 U6(a[5],b[5],cout[4],sum[5],cout[5]);

    add1 U7(a[6],b[6],cout[5],sum[6],cout[6]);

    add1 U8(a[7],b[7],cout[6],sum[7],cout[7]);

endmodule

5.8 Bcdadd100

module top_module(

    input [399:0] a, b,

    input cin,

    output cout,

    output [399:0] sum );

    wire [399:0] cout_tmp;

    bcd_fadd U1(.a(a[3:0]), .b(b[3:0]), .cin(cin), .cout(cout_tmp[0]),.sum(sum[3:0]));

    generate

        genvar i;

        for(i = 4; i < 400; i=i+4) begin : adder

            bcd_fadd fadd(.a(a[i+3:i]), .b(b[i+3:i]), .cin(cout_tmp[i-4]), .cout(cout_tmp[i]),.sum(sum[i+3:i]));

        end

    endgenerate

    assign cout = cout_tmp[396];

endmodule

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