50Mhz产生时间

原创已于 2024-11-22 13:44:12 修改 · 置顶 · 1.3w 阅读

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#fpga开发

于 2022-07-05 22:18:35 首次发布

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分频：单个时钟周期变长，频率变小，若50Mhz实现2分频，则分频后为25Mhz

倍频：单个时钟周期变短，频率变大

50Mhz 对应一个计数为0.02us,也就是20纳秒，计数到1us要50个计数，其他可自己算，下面是产生1us、1ms、1s的方法

module count_time
#(
    parameter CNT_1US_MAX = 6'd49,
    parameter CNT_1MS_MAX = 10'd999,
    parameter CNT_1S_MAX = 10'd999
)
(
    input wire sys_clk,
    input wire sys_rst_n,
    output reg  led_out
);
//50Mhz为20ns

reg [9:0]cnt_1s;     //让1ms计数到1000
reg [9:0]cnt_1ms;    //让1us计数到1000
reg [5:0]cnt_1us;  //计数到50
reg cnt_en;
//1us
always@ (posedge sys_clk or negedge sys_rst_n)
    if(sys_rst_n == 1'b0)
        cnt_1us <= 6'd0;
    else if(cnt_1us == CNT_1US_MAX)
        cnt_1us <= 6'd0;
    else 
        cnt_1us <= cnt_1us +6'd1;
 //1ms       
always@ (posedge sys_clk or negedge sys_rst_n)
    if(sys_rst_n == 1'b0)
        cnt_1ms <= 10'd0;
    else if(cnt_1ms == CNT_1MS_MAX && cnt_1us == CNT_1US_MAX)
        cnt_1ms <= 10'd0;
    else if(cnt_1us == CNT_1US_MAX)
        cnt_1ms <= cnt_1ms +10'd1;
    else
        cnt_1ms <= cnt_1ms;
 //1s      
always@ (posedge sys_clk or negedge sys_rst_n)
    if(sys_rst_n == 1'b0)
        cnt_1s <= 10'd0;
    else if(cnt_1s == CNT_1S_MAX && cnt_1ms == CNT_1MS_MAX && cnt_1us == CNT_1US_MAX)
        cnt_1s <= 10'd0;
    else if(cnt_1us == CNT_1US_MAX && cnt_1ms == CNT_1MS_MAX )
        cnt_1s <= cnt_1s + 10'd1;
    else
        cnt_1s <= cnt_1s;
        
//控制状态        
always@ (posedge sys_clk or negedge sys_rst_n)
    if(sys_rst_n == 1'b0)
        cnt_en <= 1'b0;
    else if(cnt_1s == CNT_1S_MAX && cnt_1ms == CNT_1MS_MAX && cnt_1us == CNT_1US_MAX)
        cnt_en <= ~cnt_en;
    else 
        cnt_en <= cnt_en;
        
always@ (posedge sys_clk or negedge sys_rst_n)
    if(sys_rst_n == 1'b0)
        led_out <= 1'b1;
    else if((cnt_en == 1'b0) && (cnt_1ms <= cnt_1s) 
            || (cnt_en == 1'b1) && (cnt_1ms >= cnt_1s))
        led_out <= 1'b0;
    else 
        led_out <= 1'b1;
endmodule

时钟频率对应的时钟周期
5MHz 200ns

10MHz 100ns

20MHz 50ns

25MHz 40ns

33MHz 30ns

40MHz 25ns

50MHz 20ns

66MHz 15ns

80MHz 12ns

100MHz 10ns

120MHz 8.3ns

133MHz 7.5ns