文章目录
声明：案例和代码来自小梅哥课程，本人仅对知识点做做笔记，如有学习需要请支持官方正版。
该系列目录：
Verilog线性序列机点灯案例（一）
Verilog线性序列机点灯案例（二）
Verilog线性序列机点灯案例（三）
Verilog线性序列机点灯案例（四）
设计环境
Vivado2018.3 软件
Zynq-7000 xc7z010clg400-1 板卡
设计目标
在案例（三）中提到让一个led根据8个拨码开关的值来循环变化，每个拨码开关负责0.25秒，一共是2秒。
在任务（四）中我们需要在每次动态变化前加入1秒的空闲时间（空闲时间led是熄灭的）
设计思路
1秒的空闲时间需要一个计数器来计算，假设为counter0
2秒的动态变化可以像案例（二）中一样用两个计数器来完成，假设为counter1和counter2
counter1用来计数0.25秒，counter2在counter1每次计满时加1，最后将sw[counter2]输出给led。
需要注意的是，动态变化是从1秒空闲时间后开始的，所以counter1和counter2必须在counter0计满以后才能开始工作。
在动态变化完成后，即counter1和counter2都计满的情况下，counter0再次重新开始工作。
RTL及Testbench代码
RTL代码
rust
module led_ctrl3(
clk,
rst_n,
sw,
led_out
);
input clk;
input rst_n;
input [7:0] sw;
output reg led_out;
//counter0用于计数一秒钟
reg [25:0] counter0;
//counter1用于计数0.25秒
reg [25:0] counter1;
//counter2用于计数0到7
reg [2:0] counter2;
//标记可以闪烁了
reg flag;
//50M cycles
parameter MCNT1S = 50_000_000;
//12.5M cycles
parameter MCNT025S = 12_500_000;
//控制flag状态
//flag为0时为空闲状态，led熄灭，counter0开始计数到1秒
//flag为1时为忙碌状态，led动态闪烁，counter1和counter2正常计数
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
flag <= 0;
end else if(counter0 == MCNT1S -1 ) begin
flag <= 1;
end else if( (counter1 == MCNT025S -1) && (counter2 == 7) ) begin
flag <= 0;
end else begin
flag <= flag;
end
end
//计数空闲的1秒
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
counter0 <= 0;
end else if(flag == 0) begin
if(counter0 == MCNT1S -1)begin
counter0 <= 0;
end else begin
counter0 <= counter0 + 1;
end
end
end
//负责在flag为1时计算0.25秒
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
counter1 <= 0;
end else if(flag == 1) begin
if(counter1 == MCNT025S - 1) begin
counter1 <= 0;
end else begin
counter1 <= counter1 + 1;
end
end
end
//当flag为1时，counter2每当counter1计满时自增1
//如果counter1和counter2都计满，则进入空闲时刻
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
counter2 <= 0;
end else if(flag == 1) begin
if(counter1 == MCNT025S - 1) begin
if(counter2 == 7) begin
counter2 <= 0;
end else begin
counter2 <= counter2 + 1;
end
end
end
end
//负责根据counter2决定led_out输出
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
led_out <= 0;
end else begin
if(flag) begin
case(counter2)
0:led_out <= sw[0];
1:led_out <= sw[1];
2:led_out <= sw[2];
3:led_out <= sw[3];
4:led_out <= sw[4];
5:led_out <= sw[5];
6:led_out <= sw[6];
7:led_out <= sw[7];
endcase
end
end
end
endmoduleTestbench
rust
`timescale 1ns / 1ps
module tb_led_ctrl3();
reg clk;
reg rst_n;
reg [7:0] sw;
wire led_out;
led_ctrl3 led_ctrl3_inst0(
.clk(clk),
.rst_n(rst_n),
.sw(sw),
.led_out(led_out)
);
defparam led_ctrl3.MCNT1S = 50_000;
defparam led_ctrl3.MCNT025S = 12_500;
initial begin
clk = 1;
end
always #10 clk=~clk;
initial begin
rst_n = 0;
#205;
rst_n = 1;
sw = 8'b01010101;
#3_000_000;
sw = 8'b11110000;
#3_000_000;
$stop;
end
endmodulexdc约束
rust
set_property PACKAGE_PIN T14 [get_ports led_out]
set_property PACKAGE_PIN U18 [get_ports clk]
set_property PACKAGE_PIN F20 [get_ports rst_n]
set_property IOSTANDARD LVCMOS33 [get_ports {sw[7]}]
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 led_out]
set_property IOSTANDARD LVCMOS33 [get_ports rst_n]
set_property PACKAGE_PIN E17 [get_ports {sw[7]}]
set_property PACKAGE_PIN D18 [get_ports {sw[6]}]
set_property PACKAGE_PIN H15 [get_ports {sw[5]}]
set_property PACKAGE_PIN F16 [get_ports {sw[4]}]
set_property PACKAGE_PIN J14 [get_ports {sw[3]}]
set_property PACKAGE_PIN G14 [get_ports {sw[2]}]
set_property PACKAGE_PIN L15 [get_ports {sw[1]}]
set_property PACKAGE_PIN K14 [get_ports {sw[0]}]仿真结果
