例1:
本文引用地址://m.amcfsurvey.com/article/201611/322060.htmreg[2:0] key_rst;
always @(posedge clkor negedge rst_n)
if (!rst_n) key_rst <= 3b111;
else key_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 @ ( posedge clkor negedge rst_n )
if (!rst_n) key_rst_r <= 3b111;
else key_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);
例2:
//说明: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
module sw_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 @(posedge clkor negedge rst_n)
if (!rst_n) key_rst <= 3`b111;
else key_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 @ ( posedge clkor negedge rst_n )
if (!rst_n) key_rst_r <= 3`b111;
else key_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);
//-----------------------------------------------------------------
reg[19:0]cnt;//计数寄存器
always @ (posedge clkor negedge rst_n)
if (!rst_n) cnt <= 20`d0;//异步复位
else if(key_an) cnt <=20`d0;
else cnt <= cnt + 1`b1;
reg[2:0] low_sw;
always @(posedge clkor negedge rst_n)
if (!rst_n) low_sw <= 3`b111;
else if (cnt == 20`hfffff) //满20ms,将按键值锁存到寄存器low_sw中cnt == 20hfffff
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
always @ ( posedge clkor negedge rst_n )
if (!rst_n) low_sw_r <= 3`b111;
else low_sw_r <= low_sw;
//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]);
reg d1;
reg d2;
reg d3;
always @(posedge clk or negedge rst_n)
if (!rst_n)
begin
d1 <= 1b0;
d2 <= 1b0;
d3 <= 1b0;end
else
begin//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
assign led_d3 = d1 ? 1`b1 : 1`b0;//LED翻转输出
assign led_d2 = d2 ? 1`b1 : 1`b0;
assign led_d1 = d3 ? 1`b1 : 1`b0;
endmodule
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