题解 | #交通灯#
交通灯
https://www.nowcoder.com/practice/b5ae79ff08804b61ad61f749eaf157ba
运行一直是错的。。。为啥答案的波形倒计时到8之后突然又成10了啊。。。
`timescale 1ns/1ns
module triffic_light
(
input rst_n, //异位复位信号，低电平有效
input clk, //时钟信号
input pass_request,
output wire[7:0]clock,
output reg red,
output reg yellow,
output reg green
);
parameter S0 = 'd0;
parameter S1 = 'd1;
parameter S2 = 'd2;
parameter S3 = 'd3;
reg [5:0] cnt;
reg [1:0] cstate, nstate;
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
cstate <= S0;
end
else begin
cstate <= nstate;
end
end
always@(*) begin
case(cstate)
S0: begin
nstate = (cnt=='d9)?S1:S0;
end
S1: begin
nstate = (cnt=='d4)?S2:S1;
end
S2: begin
nstate = (cnt=='d59)?S0:S2;
end
default: begin
nstate = S0;
end
endcase
end
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
cnt <= 'd0;
end
else begin
if(pass_request & (cstate==S3) & (cnt>='d10)) begin
cnt <= 'd10;
end
else begin
if(cstate!=nstate) begin
cnt <= 'd0;
end
else begin
cnt <= cnt + 'd1;
end
end
end
end
assign clock = (cstate==S0)?('d10-cnt):((cstate==S1)?('d5-cnt):('d60-cnt));
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
{red,yellow,green} <= 'd0;
end
else begin
{red,yellow,green} <= {(cstate==S0),(cstate==S1),(cstate==S2)};
end
end
endmodule
