1、半整數(shù)分頻占空比不為50%
//說明：設(shè)計(jì)的史上最好用的半整數(shù)分頻占空比不為50%，包含設(shè)計(jì)思路
module div_5(clk,clk_div,cnt1,cnt2,temp1,temp2);//N+0.5
input clk;
output clk_div;
output reg[31:0]cnt1,cnt2;
output reg temp1,temp2;
initial begin temp1=0;temp2=1;end //首先進(jìn)行初始化，temp1=0;temp2=1
parameter N=5; //設(shè)定分頻系數(shù)為N+0.5
always @(posedge clk) //temp1上升沿跳變
begin
if(cnt1==2*N) //2*N
begin cnt1[31:0]<=32'd0;end
else begin cnt1[31:0]<=cnt1[31:0]+32'd1;end
if(cnt1==32'd0) begin temp1<=1;end //高電平時(shí)間為N+1;
if(cnt1==N+1) begin temp1<=0;end //低電平時(shí)間為N;
end
always@(negedge clk) //temp2下降沿跳變
begin
if(cnt2==2*N) //2*N
begin cnt2[31:0]<=32'd0;end
else begin cnt2[31:0]<=cnt2[31:0]+32'd1;end
if(cnt2==32'd0) begin temp2<=0;end //低電平時(shí)間為N;
if(cnt2==N) begin temp2<=1;end //高電平時(shí)間為N+1;
end
assign clk_div=temp1&&temp2; //邏輯與
endmodule
//如果要進(jìn)行N+0.5分頻
//思路：總的來說要進(jìn)行N+1+N=2N+1次分頻
//在時(shí)鐘的上升沿和下降沿都進(jìn)行跳變
//上升沿進(jìn)行占空比為N+1比N的時(shí)鐘temp1;
//下降沿進(jìn)行占空比為N比N+1的時(shí)鐘temp2;
//最后div=temp1&&temp2 即可得到所需要的半整數(shù)分頻
2、奇數(shù)分頻占空比為50%
//說明：奇數(shù)分頻。
module div_5(clk,clk_div,cnt1,cnt2,temp1,temp2);//
input clk;
output clk_div;
output reg[31:0]cnt1,cnt2;
output reg temp1,temp2;
parameter N=5; //設(shè)定分頻系數(shù)
always @(posedge clk)
begin
if(cnt1==N-1) //N-1進(jìn)行N計(jì)數(shù)
begin cnt1[31:0]<=32'd0;end
else begin cnt1[31:0]<=cnt1[31:0]+32'd1;end
if(cnt1==32'd0) begin temp1<=1;end //
if(cnt1==(N-1)/2) begin temp1<=0;end //當(dāng)計(jì)數(shù)到(N-1)/2時(shí)翻轉(zhuǎn)
end
always@(negedge clk)
begin
if(cnt2==N-1) //N-1
begin cnt2[31:0]<=32'd0;end
else begin cnt2[31:0]<=cnt2[31:0]+32'd1;end
if(cnt2==32'd0) begin temp2<=1;end //;
if(cnt2==(N-1)/2) begin temp2<=0;end //當(dāng)計(jì)數(shù)到(N-1)/2時(shí)翻轉(zhuǎn);
end
assign clk_div=temp1||temp2; //邏輯或
endmodule
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