`timescale1ns/1ps
//当三个独立按键的某一个被按下后，相应的LED被点亮；再次按下后，LED熄灭，按键控制LED亮灭
modulesw_debounce(
		clk,rst_n,
	sw1_n,sw2_n,sw3_n,
	led_d1,led_d2,led_d3
		);
inputclk;	//主时钟信号，50MHz
inputrst_n;	//复位信号，低有效
inputsw1_n,sw2_n,sw3_n;	//三个独立按键，低表示按下
outputled_d1,led_d2,led_d3;	//发光二极管，分别由按键控制
//---------------------------------------------------------------------------
reg[2:0]key_rst;/////
always@(posedgeclkornegedgerst_n)
if(!rst_n)key_rst<=3'b111;
elsekey_rst<={sw3_n,sw2_n,sw1_n};
reg[2:0]key_rst_r;//每个时钟周期的上升沿将low_sw信号锁存到low_sw_r中
always@(posedgeclkornegedgerst_n)
if(!rst_n)key_rst_r<=3'b111;
elsekey_rst_r<=key_rst;
//当寄存器key_rst由1变为0时，led_an的值变为高，维持一个时钟周期
wire[2:0]key_an=key_rst_r&(~key_rst);
/*
key_rst111001
~key_rst000110
key_rst_n111001
key_an00100
*/
//---------------------------------------------------------------------------
reg[19:0]cnt;	//计数寄存器
always@(posedgeclkornegedgerst_n)
if(!rst_n)cnt<=20'd0;	//异步复位
	elseif(key_an)cnt<=20'd0;
elsecnt<=cnt+1'b1;
reg[2:0]low_sw;
always@(posedgeclkornegedgerst_n)
if(!rst_n)low_sw<=3'b111;
elseif(cnt==20'hfffff)	//满20ms，将按键值锁存到寄存器low_sw中	cnt==20'hfffff
low_sw<={sw3_n,sw2_n,sw1_n};
//---------------------------------------------------------------------------
reg[2:0]low_sw_r;//每个时钟周期的上升沿将low_sw信号锁存到low_sw_r中

always@(posedgeclkornegedgerst_n)
if(!rst_n)low_sw_r<=3'b111;
elselow_sw_r<=low_sw;
/*
low_sw		111111111110110110
~low_sw000000000001001001
low_sw_r111111111110110110

led_ctrl	000000000001000000
*/
//当寄存器low_sw由1变为0时，led_ctrl的值变为高，维持一个时钟周期
wire[2:0]led_ctrl=low_sw_r[2:0]&(~low_sw[2:0]);
regd1;
regd2;
regd3;
always@(posedgeclkornegedgerst_n)
if(!rst_n)begin
d1<=1'b0;
d2<=1'b0;
d3<=1'b0;
end
elsebegin		//某个按键值变化时，LED将做亮灭翻转
if(led_ctrl[0])d1<=~d1;	
if(led_ctrl[1])d2<=~d2;
if(led_ctrl[2])d3<=~d3;
end

assignled_d3=d1?1'b1:1'b0;		//LED翻转输出
assignled_d2=d2?1'b1:1'b0;
assignled_d1=d3?1'b1:1'b0;

endmodule