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VL24 边沿检测

预备知识：

1.非时钟信号的边沿检测方法：

reg data_dly;always @(posedge clk)begin data_pre<=data;//当前的data存储起来end wire data_rising_edge=data&~data_pre;//当前的1、上一拍的0wire data_falling_edge=~data&data_pre;

2.对时钟信号本身做边沿检测
直接使用 posedge clk 或 negedge clk 。

题目要求

思路一：

`timescale1ns/1ns moduleedge_detect(input clk,input rst_n,input a,output reg rise,output reg down);reg a_pre;always @(posedge clk)begin a_pre<=a;end always @(posedge clk,negedge rst_n)beginif(!rst_n)begin rise<=0;down<=0;endelsebeginif(a&~a_pre)begin rise<=1;down<=0;endelseif(a_pre&~a)begin rise<=0;down<=1;endelsebegin rise<=0;down<=0;end end end endmodule

思路二：

`timescale1ns/1ns moduleedge_detect(input clk,input rst_n,input a,output reg rise,output reg down);reg a_pre;always @(posedge clk,negedge rst_n)beginif(!rst_n)begin rise<=0;down<=0;a_pre<=0;endelsebegin a_pre<=a;rise<=(a&~a_pre)?1:0;down<=(a_pre&~a)?1:0;end end endmodule

思路二报错：

大佬可否给个提示?为啥会错呢？感觉思路一和思路二没区别啊