本章節(jié)簡(jiǎn)介：

可以在任意時(shí)刻啟動(dòng)，可以重復(fù)啟動(dòng)，延時(shí)時(shí)長(zhǎng)可調(diào)，單位可切換（ms/us），在50MHz時(shí)鐘下的延時(shí)范圍是1ms-85899ms/1us-85899us。

源代碼和modelsim仿真代碼：

moduledelay



//#(parameterN)//可以延時(shí)N*1ms/us



(inputclk,rst_n,

inputstart,//start上升沿有效

inputdelay_unit,//延時(shí)單位，high:ms/low:us

outputfinish,finish_pose);//finish上升沿有效

regstart_reg0,start_reg1;//start兩級(jí)緩存，用于邊沿檢測(cè)

regfinish_reg0,finish_reg1;//finish兩級(jí)緩存

reg[31:0]cnt;//固定32位寬計(jì)數(shù)

reg[31:0]cnt_full;

regrestart;//重新開始

wirestart_pose,full;

always@(posedgeclkornegedgerst_n)

begin

if(!rst_n)

begin

cnt<=?32'd0;

???????????????????cnt_full?<=?32'd10;?//避免一開始finish置位

???????????????????restart?<=?1'b0;

???????????????????start_reg0?<=?1'b0;?start_reg1?<=?1'b0;?

???????????????????finish_reg0?<=?1'b0;?finish_reg1?<=?1'b0;

???????????????end

???????????else

??????????????begin

??????????????????start_reg0?<=?start;?start_reg1?<=?start_reg0;

??????????????????finish_reg1?<=?finish_reg0;??

??????????????????/**檢測(cè)計(jì)時(shí)單位**/

??????????????????if(delay_unit)??

?????????????????????cnt_full?<=?32'd50_000*2-32'd2;??//計(jì)時(shí)2ms??實(shí)際例化時(shí)用N代替:?32'd50_000*N-32'd2

??????????????????else

?????????????????????cnt_full?<=?32'd50*2-32'd2;??????//計(jì)時(shí)2us

?????????????????/***************/

????????????????/**是否重新開始**/

????????????????if(start_pose)??//檢測(cè)到起始時(shí)刻?

????????????????????restart?<=?1'b1;??

???????????????/****計(jì)時(shí)完成****/

???????????????else?if(full)??//延時(shí)結(jié)束

??????????????????begin

??????????????????????cnt?<=?32'd0;??//cnt歸零

??????????????????????finish_reg0?<=?1'b1;??//finish響應(yīng)

??????????????????????restart?<=?1'b0;

??????????????????end

?????????????/***************/

?????????????/****計(jì)時(shí)開始****/

?????????????else?if(restart)?

????????????????begin

????????????????????finish_reg0?<=?1'b0;????//新一輪延時(shí)finish復(fù)位

????????????????????cnt?<=?cnt+1'b1;

????????????????end

???????????/***************/

???????????/**等待新一輪計(jì)時(shí)**/

???????????else?

??????????????begin

??????????????????cnt?<=?cnt;

??????????????????finish_reg0?<=?finish_reg0;

??????????????????restart?<=?restart;

??????????????end

????end??

end

?

??assign?start_pose?=?(~start_reg1&start_reg0)?1'b1:1'b0;??//start上升沿檢測(cè)

??assign?finish_pose?=?(~finish_reg1&finish_reg0)?1'b1:1'b0;??//finish上升沿檢測(cè)

??assign?full?=?(cnt_full-cnt==0)?1'b1:1'b0;???//檢測(cè)是否計(jì)滿



??assign?finish?=?finish_reg0;



endmodule



/**************************************************************************************************/?????????????????????????????????????/***************************************modelsim********************************************/??



`timescale?1ns/1ps

module?delay_tb();

???reg?clk,rst_n;

???reg?start;

???wire?finish,finish_pose;

??

??delay?delay_u0

??(.clk(clk),

???.rst_n(rst_n),

???.start(start),

???.delay_unit(1'b1),

???.finish(finish),

???.finish_pose(finish_pose));

???//defparam?delay_u0.N?=?2;?//延時(shí)2ms

??

??initial

????begin

clk?=?1'b0;

????????rst_n?=?1'b0;

????????start?=?1'b0;

#1000?rst_n?=?1'b1;

#4010?start?=?1'b1;?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????#50?????start?=?1'b0;????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????end



??always?#10?clk?=?~clk;

endmodule

思路：

start端口給上升沿啟動(dòng)延時(shí)，延時(shí)結(jié)束端口finish置位（重新啟動(dòng)延時(shí)后復(fù)位）、finish的上升沿檢測(cè)在模塊內(nèi)部已做好（端口finish_pose），直接調(diào)用即可，端口delay_unit置高選擇ms，置低選擇us，#（參數(shù)N ）“是計(jì)時(shí)時(shí)長(zhǎng)，例如計(jì)時(shí)8ms：”N = 8， .delay_unit（1'b1）“，實(shí)際例化時(shí)只需”defparam 例化名.N = 數(shù)值”。因?yàn)閙odelsim無法識(shí)別這種調(diào)用，所以直接用數(shù)值代替N進(jìn)行測(cè)試。邊沿檢測(cè)會(huì)消耗兩個(gè)時(shí)鐘周期，所以cnt_full需要減2，并且將finish_reg0直接連到finish輸出端口而不是用finish_reg1連接完成。

延時(shí)2ms測(cè)試的起始時(shí)刻（5010ns）和結(jié)束時(shí)刻（2005010ns）：