基于FPGA的ds18b20温度传感器设计程序.doc

module temper(input clk,input rst_n,inout one_wire,output [15:0] temperature); // 分频器20MHz-1MHz 开始 reg [3:0] cnt; reg clk_1us; always @ (posedge clk, negedge rst_n) if (!rst_n) cnt = 0; else if (cnt == 9) begin cnt = 0;clk_1us= ~ clk_1us;end else cnt = cnt + 4d1; // 1MHz 时钟 //延时模块的使用 reg [19:0] cnt_1us; reg cnt_1us_clear; always @ (posedge clk_1us) if (cnt_1us_clear) cnt_1us = 0; else cnt_1us = cnt_1us + 1b1; // DS18B20状态机开始 // 格雷码 parameter S00 = 5h00; parameter S0 = 5h01; parameter S1 = 5h03; parameter S2 = 5h02; parameter S3 = 5h06; parameter S4 = 5h07; parameter S5 = 5h05; parameter S6 = 5h04; parameter S7 = 5h0C; parameter WRITE0 = 5h0D; parameter WRITE1 = 5h0F; parameter WRITE00 = 5h0E; parameter WRITE01 = 5h0A; parameter READ0 = 5h0B; parameter READ1 = 5h09; parameter READ2 = 5h08; parameter READ3 = 5h18; reg [4:0] state; // 状态寄存器 //------------------------------------- reg one_wire_buf; // One-Wire总线缓存寄存器reg [15:0] temperature_buf; // 采集到的温度值缓存器 reg [5:0] step; // 子状态寄存器0~50 reg [3:0] bit_valid; // 有效位 always @(posedge clk_1us, negedge rst_n) begin if (!rst_n) begin one_wire_buf = 1bZ; step = 0; state = S00; end else begin case (state) S00 : begin temperature_buf = 16h001F; state = S0; end S0 : begin // 初始化 cnt_1us_clear = 1; one_wire_buf = 0; state = S1; end S1 : begin cnt_1us_clear = 0; if (cnt_1us == 500) // 延时500us begin cnt_1us_clear = 1; one_wire_buf = 1bZ; // 释放总线 state = S2; end end S2 : begin cnt_1us_clear = 0; if (cnt_1us == 100) // 等待100us begin cnt_1us_clear = 1; state = S3; end end S3 : if (~one_wire) // 若18b20拉低总线,初始化成功state = S4; else if (one_wire) // 否则,初始化不成功,返回S0 state = S0; S4 : begin cnt_1us_clear = 0; if (cnt_1us == 400) // 再延时400us begin cnt_1us_clear = 1; state = S5; end end S5 : begin // 写数据 if (step == 0) // 0xCC begin step = step + 1b1; state = WRITE0; end else if (step == 1) begin step = step + 1b1; state = WRITE0; end else if (s