目录
一.设计要求
二.模块总和
三.模块设计
1.顶层模块
2.分频模块
3.计数模块
4.倒计时模块
5.数码显示模块
6.管脚约束代码
四.引脚分配
五.演示视频
一、设计要求
①.用基于NEXY4 DDR开发板自带的时钟驱动电路，要求计时精确；
②.用开发板上的低 7 个开关（sw6-sw0），输入倒计时的初始秒数（最大 99）；
③.用 2 个数码管以十进制显示当前的倒计时秒值；
④.用最高的开关（若开发板开关不够，可以用按键代替）实现 reset 功能；reset 后，能以 新的开关值进行倒计时。
⑤.当倒计时到 0 秒后，返回初始值继续倒计时。
二、模块总和
三、模块设计
1.顶层模块
module top(
input clk,
input rst_n,
input [6:0]sw,
output [7:0]sel,
output [7:0]seg
);
wire clk_1s;
wire [6:0]cnt;
wire [3:0]en1;
wire [3:0]en2;
div div(
.clk(clk),
.rst_n(rst_n),
.clk_1s(clk_1s)
);
count count(
.clk(clk_1s),
.rst_n(rst_n),
.sw(sw),
.cnt(cnt)
);
countdown countdown(
.clk(clk),
.rst_n(rst_n),
.cnt(cnt),
.en1(en1),
.en2(en2)
);
digital digital(
.clk(clk),
.rst_n(rst_n),
.en1(en1),
.en2(en2),
.seg(seg),
.sel(sel)
);
endmodule2.分频模块
module div(
input clk,
input rst_n,
output reg clk_1s
);
reg [29:0]counter1;//计数器技术满0.5ms需要30位宽的计数器
always @(posedge clk or negedge rst_n)
if(!rst_n)
counter1 <= 0;
else if(counter1 == 49999999)
counter1 <= 0;
else
counter1 <= counter1 + 1;
always @(posedge clk or negedge rst_n)
if(!rst_n)
clk_1s <= 0;
else if(counter1 == 49999999)
clk_1s <= ~clk_1s;
else
clk_1s <= clk_1s;
endmodule3.计数模块
module count(
input clk,
input rst_n,
input [6:0]sw,
output reg [6:0]cnt //倒计时最大值99s
);
always @(negedge clk or negedge rst_n)
if(!rst_n)
begin
if(sw == 7'b000_0001)
cnt <= 7'd1;
else if(sw == 7'b000_0010)
cnt <= 7'd5;
else if(sw == 7'b000_0100)
cnt <= 7'd10;
else if(sw == 7'b000_1000)
cnt <= 7'd20;
else if(sw == 7'b001_0000)
cnt <= 7'd25;
else if(sw == 7'b010_0000)
cnt <= 7'd30;
else if(sw == 7'b100_0000)
cnt <= 7'd35;
else
cnt <= 0;
end
else if(cnt == 7'd99)
cnt <= 0;
else
cnt <= cnt + 1;
endmodule4.倒计时模块
module countdown(
input clk,
input rst_n,
input [6:0]cnt,
output reg [3:0]en1,//个位
output reg [3:0]en2//十位
);
always @(posedge clk or negedge rst_n)
if(!rst_n)
begin
en1 <= 0;
en2 <= 0;
end
else if(cnt <= 7'd99)
begin
en1 <= (99-cnt)%10;
en2 <= ((99-cnt)-en1)/10;
end
endmodule5.数码显示模块
module digital(
input clk,
input rst_n,
input [3:0]en1,
input [3:0]en2,
output reg [7:0]seg,
output reg [7:0]sel
);
//计数1ms
reg [16:0]counter2;//计数1ms 1000000/10= 100000
always @(posedge clk or negedge rst_n)
if(!rst_n)
counter2 <= 0;
else if(counter2 == 99999)
counter2 <= 0;
else
counter2 <= counter2 + 1;
//1ms时钟使能
reg clk_1ms_en;
always @(posedge clk or negedge rst_n)
if(!rst_n)
clk_1ms_en <= 0;
else if(counter2 == 99999)
clk_1ms_en <= 1;
else
clk_1ms_en <= 0;
//8位数码管计数器
reg [2:0]counter3;
always @(posedge clk or negedge rst_n)
if(!rst_n)
counter3 <= 0;
else if(clk_1ms_en)
counter3 <= counter3 + 1;
else
counter3 <= counter3;
//8位数码管选择
always @(posedge clk)
case(counter3)
0:sel <= 8'b1111_1110;
1:sel <= 8'b1111_1101;
2:sel <= 8'b1111_1111;
3:sel <= 8'b1111_1111;
4:sel <= 8'b1111_1111;
5:sel <= 8'b1111_1111;
6:sel <= 8'b1111_1111;
7:sel <= 8'b1111_1111;
endcase
wire[31:0]data;
assign data[3:0] = en1;
assign data[7:4] = en2;
reg [3:0]dsp_data;
always @(posedge clk)
case(counter3)
0:dsp_data <= data[3:0];
1:dsp_data <= data[7:4];
2:dsp_data <= data[11:8];
3:dsp_data <= data[15:12];
4:dsp_data <= data[19:16];
5:dsp_data <= data[23:20];
6:dsp_data <= data[27:24];
7:dsp_data <= data[31:28];
endcase
always @(posedge clk)
case(dsp_data)
4'd0:seg <= 8'b1100_0000;
4'd1:seg <= 8'b1111_1001;
4'd2:seg <= 8'b1010_0100;
4'd3:seg <= 8'b1011_0000;
4'd4:seg <= 8'b1001_1001;
4'd5:seg <= 8'b1001_0010;
4'd6:seg <= 8'b1000_0010;
4'd7:seg <= 8'b1111_1000;
4'd8:seg <= 8'b1000_0000;
4'd9:seg <= 8'b1001_0000;
endcase
endmodule
6.管脚约束代码
set_property IOSTANDARD LVCMOS33 [get_ports {seg[7]}]
set_property IOSTANDARD LVCMOS33 [get_ports {seg[6]}]
set_property IOSTANDARD LVCMOS33 [get_ports {seg[5]}]
set_property IOSTANDARD LVCMOS33 [get_ports {seg[4]}]
set_property IOSTANDARD LVCMOS33 [get_ports {seg[3]}]
set_property IOSTANDARD LVCMOS33 [get_ports {seg[2]}]
set_property IOSTANDARD LVCMOS33 [get_ports {seg[1]}]
set_property IOSTANDARD LVCMOS33 [get_ports {seg[0]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[7]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[6]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[5]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[4]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[3]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[2]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[1]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sel[0]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[6]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[5]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[4]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[3]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[2]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[1]}]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[0]}]
set_property IOSTANDARD LVCMOS33 [get_ports clk]
set_property IOSTANDARD LVCMOS33 [get_ports rst_n]
set_property PACKAGE_PIN C12 [get_ports rst_n]
set_property PACKAGE_PIN E3 [get_ports clk]
set_property PACKAGE_PIN J15 [get_ports {sw[0]}]
set_property PACKAGE_PIN L16 [get_ports {sw[1]}]
set_property PACKAGE_PIN M13 [get_ports {sw[2]}]
set_property PACKAGE_PIN R15 [get_ports {sw[3]}]
set_property PACKAGE_PIN R17 [get_ports {sw[4]}]
set_property PACKAGE_PIN T18 [get_ports {sw[5]}]
set_property PACKAGE_PIN U18 [get_ports {sw[6]}]
set_property PACKAGE_PIN U13 [get_ports {sel[7]}]
set_property PACKAGE_PIN K2 [get_ports {sel[6]}]
set_property PACKAGE_PIN T14 [get_ports {sel[5]}]
set_property PACKAGE_PIN P14 [get_ports {sel[4]}]
set_property PACKAGE_PIN J14 [get_ports {sel[3]}]
set_property PACKAGE_PIN T9 [get_ports {sel[2]}]
set_property PACKAGE_PIN J18 [get_ports {sel[1]}]
set_property PACKAGE_PIN J17 [get_ports {sel[0]}]
set_property PACKAGE_PIN H15 [get_ports {seg[7]}]
set_property PACKAGE_PIN L18 [get_ports {seg[6]}]
set_property PACKAGE_PIN T11 [get_ports {seg[5]}]
set_property PACKAGE_PIN P15 [get_ports {seg[4]}]
set_property PACKAGE_PIN K13 [get_ports {seg[3]}]
set_property PACKAGE_PIN K16 [get_ports {seg[2]}]
set_property PACKAGE_PIN R10 [get_ports {seg[1]}]
set_property PACKAGE_PIN T10 [get_ports {seg[0]}]四、引脚分配
文章来源：https://www.toymoban.com/news/detail-752133.html
五、演示视频
IMG_2222文章来源地址https://www.toymoban.com/news/detail-752133.html
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