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编程题
1.设计一个全加器电路，并写出测试代码。
//数据流建模
module ADD1(sum,c_out,A,B,c_in);
input A,B,c_in;
output c_out,sum;
assign sum = (A^B)^c_in;
assign c_out = (A&B)|((A^B)&c_in);
endmodule
module test;
reg A,B,c_in;
wire c_out,sum;
ADD1 ut(sum,c_out,A,B,c_in);
initial
begin
A=1'b0;
B=1'b1;
c_in=1'b0;
#50 A=1'b1;
c_in=1'b1;
#50 B=1'b0;
c_in=1;b0;
end
endmodule//行为级建模
module ADD1(sum,c_out,A,B,c_in);
output sum,c_out;
input A,B,c_in;
assign {c_out,sum} = A+B+c_in;
endmodule
2.设计一个带复位端且输入时钟clk进行多种分频模块。
设计要求：复位信号为同步、低电平有效，时钟的上升沿触发，要求包括测试电路，并画出仿真波形。
module addr(count,clk,rst,qout);
input clk,rst;
output reg [31:0] count;
always@ (posedge clk)
begin
if(!rst) count = 0;
else count = count+1;
end
assign qout <= count[0];//二分频
endmodule
module test;
reg clk;
reg rst;
addr ut(count,clk,rst);
always #20 clk = ~clk;
initial
begin
clk = 1'b0;
rst = 1'b0;
#20 rst = 1'b1;
end
endmodule3.设计一个奇偶校验位生成电路，输入八位总线信号bus，输出奇校验位odd，偶校验位even。
module parity(even,odd,bus);
output even,odd;
input[7:0] bus; //奇同偶异
assign even = ^bus; //偶校验用异或
assign odd = ^~bus; //奇校验用同或
endmodule4.设计一个带异步复位端、异步置数端（低电平有效）的四位十进制加法计数器，时钟clk上升沿有效，复位信号clr，置数信号load，输入数据data、输出qout。并画出仿真波形图。
module addr_4(qout,clr,clk,load,data);
output reg [3:0] qout;
input[3:0] data;
input load,clr,clk;
always@ (posedge clk or negedge load or negedge clr)
begin
if(clr)
qout<=0;
else if(!load)
qout<=data;
else if(qout<9)
qout<=qout+1;
else
qout = 1'b0;
end
endmodule
module test;
reg clk,clr,load;
reg [3:0] data;
reg [3:0] qout;
addr_4 ut(qout,clr,clk,load,data);
always #10 clk = ~clk;
initial
begin
clk = 0;
clr = 1'b1;
load = 1'b0;
data = 4'b0100;
#20 clr = 1'b0;
#20 load = 1'b1;
clr = 1'b1;
#20 load = 1'b0;
end
endmodule5.数据选择器
//抽象描述方式
//8选1数据选择器
module mux8to1(out,sel,data_in);
output reg out;
input [7:0] data_in;
input [2:0] sel;
always@ (data_in or sel)
case(sel)
3'b000 : out <= data_in[0];
3'b001 : out <= data_in[1];
3'b010 : out <= data_in[2];
3'b011 : out <= data_in[3];
3'b100 : out <= data_in[4];
3'b101 : out <= data_in[5];
3'b110 : out <= data_in[6];
3'b111 : out <= data_in[7];
endcase
endmodule
//4选1数据选择器
module mux4to1(out,sel,data_in);
output reg out;
input [3:0] data_in;
input [1:0] sel;
always@ (data_in or sel)
case(sel)
2'b00 : out <= data_in[0];
2'b01 : out <= data_in[1];
2'b10 : out <= data_in[2];
2'b11 : out <= data_in[3];
endcase
endmodule
6. 任意进制加/减法计数器
对于M进制的计数器，第一步需要确定计数器所需要触发器的个数。N个触发器对应了2^N个状态，应有2^N>M。任意进制计数器选取满足条件的最小N，N为计数器中触发器的个数。
//十一进制加法计数器，反馈清零法
module comp_11(count,clk,rst)
output reg [3:0] count;
input clk,rst;
always@ (posedge clk)
if(rst) count <= 4'b0000; //复位清零
else
if(count == 4'b1010) //计数到10时清零
count <= 1'b0;
else
count <= count+1; //加法计数
endmodule7.移位寄存器
//4位循环左移
module shiftregist1(Q,clk,reset);
parameter shiftregist_width=4;
output [shiftregist_width-1:0] Q;
input clk,reset;
reg [shiftregist_width-1:0] Q;
always @(posedge clk)
if (!reset)
Q<=4‘b0000;
else
Q<={Q[shiftregist_width-2:0],Q[shiftregist_width-1]};
endmodule8.2输入8位加法器
//行为描述方式
module eight_bits_fulladder(sum,c_out,a,b,c_in)
output [7:0] sum;
output c_out;
input [7:0] a,b;
input c_in;
assign {c_out,sum} = a+b+c_in;
endmodule9.ROM
module rom(dout,clk,addm,cs_n)
input clk,cs_n;
input [2:0] addm;
output reg [7:0] dout;
reg [7:0] rom[7:0];
initial
begin
rom[0] = 8'b0000_0000;
rom[1] = 8'b0000_0001;
rom[2] = 8'b0000_0010;
rom[3] = 8'b0000_0011;
rom[4] = 8'b0000_0100;
rom[5] = 8'b0000_0101;
rom[6] = 8'b0000_0110;
rom[7] = 8'b0000_0111;
end
always@ (posedge clk)
begin
if(cs_n) dout <= 8'bzzzz_zzzz;
else dout <= rom[addm];
end
endmodule
module rom_tb;
reg clk;
reg [2:0] addm;
reg cs_n;
wire [7:0] dout ;
rom PB2(.clk(clk),.addm(addm),.cs_n(cs_n),.dout(dout));
always #10 clk = ~clk;
initial
begin
clk = 0;
addm =0;
cs_n = 0;
end
initial
begin
repeat(7)
#20 addm = addm +1;
end
endmodule10.RAM
module ram(input clk,
input [4:0] addm,
input cs_n,
input we_n,
input [7:0] din,
output reg [7:0]dout);
reg [7:0] ram[31:0];
always @(posedge clk)
begin
if(cs_n) dout <= 8'bzzzz_zzzz;
else
if(we_n) dout <= ram[addm];
else ram[addm] <= din;
end
endmodule
`timescale 1ns/1ps;
module TestRam;
reg clk;
reg [4:0] addm;
reg cs_n;
reg we_n;
reg [7:0] din;
wire [7:0] dout;
ram PB1(.clk(clk),.addm(addm),.cs_n(cs_n),.we_n(we_n),.din(din),.dout(dout));
initial
begin
clk = 0;
addm = 0;
cs_n = 1;
we_n = 0;
din = 0;
#5
cs_n = 0;
#1265
we_n = 1;
end
always #10 clk = ~clk;
initial
begin
repeat(31)
begin
#40 addm = addm +1;
din = din+1;
end
#40 repeat(31)
#40 addm = addm -1;
end
endmodule11.序列检测
//序列检测“111”，moore型
module FSM_moore(input clk,
input rst,
input data,
output result);
parameter ST0 = 4'b000;
parameter ST1 = 4'b001;
parameter ST2 = 4'b010;
parameter ST3 = 4'b100;
reg [3:0] c_state;
reg [3:0] n_state;
always@ (posedge clk)
if(!rst) c_state <= ST0;
else c_state <= n_state;
always@ (c_state,data)
case(c_state)
ST0:
if(data == 1'b1) n_state = ST1;
else n_state = ST0;
ST1:
if(data == 1'b1) n_state = ST2;
else n_state = ST0;
ST2:
if(data == 1'b1) n_state = ST3;
else n_state = ST0;
ST3:
if(data == 1'b1) n_state = ST3
else n_state = ST0;
default: n_state = ST0;
endcase
assign result = (c_state == ST3) ? 1 :0;
endmodule
module FSM_tb;
reg clk,rst,data;
wire moore;
FSM_moore U_moore(.clk(clk),
.rst(rst),
.data(data),
.result(result));
always #10 clk = ~clk;
initial
begin
#0 clk = 1;
rst = 0;
data = 0;
#20 rst = 1'b1;
#20 data = 1'b1;
#20 data = 1'b1;
#20 data = 1'b0;
#20 data = 1'b1;
#20 data = 1'b1;
#20 data = 1'b1;
end
endmodule