在读本文之前，请先阅读 LCD1602 的 datasheet（百度到处都是） ,熟悉有关的11条指令集。
LCD1602的11个指令集链接 http://www.cnblogs.com/aslmer/p/5801363.html（这是我总结的11条指令集，中英文结合）
1、LCD1602基础知识
（2）LCD1602操作流程
2、代码：
module lcd_1602_driver(
clk ,
rst_n ,
lcd_en ,
lcd_rw , //因为只执行写操作，所以永远为0.
lcd_rs ,
lcd_data
);
input clk ;
input rst_n ;
output lcd_en ;
output lcd_rw ;
output lcd_rs ;
output [7:0] lcd_data;
wire clk ;
wire rst_n ;
wire lcd_en ;
wire lcd_rw;
reg [7:0] lcd_data;
reg lcd_rs ;
reg [5:0] c_state ;
reg [5:0] n_state ;
wire [127:0] row_1;
wire [127:0] row_2;
assign row_1 ="i am liu xiao yi" ; //第一行显示的内容
assign row_2 ="happy everyday !"; //第二行显示的内容
//----------------------------------------------------------------------
//initialize
//first step is waitng more than 20 ms. 数据手册要求的，目的是等待系统上电稳定。
parameter TIME_20MS = 1000_000 ; //20000000/20=1000_000
//parameter TIME_15MS = 9'h100 ; //just for test
parameter TIME_500HZ= 100_000 ; //
//parameter TIME_500HZ= 4'hf; //just for test
//use gray code
parameter IDLE= 8'h00 ; //因为此状态机一共有40个状态，所以这里用了格雷码，一次只有1位发生改变。00 01 03 02
parameter SET_FUNCTION= 8'h01 ;
parameter DISP_OFF= 8'h03 ;
parameter DISP_CLEAR= 8'h02 ;
parameter ENTRY_MODE= 8'h06 ;
parameter DISP_ON = 8'h07 ;
parameter ROW1_ADDR= 8'h05 ;
parameter ROW1_0= 8'h04 ;
parameter ROW1_1= 8'h0C ;
parameter ROW1_2= 8'h0D ;
parameter ROW1_3= 8'h0F ;
parameter ROW1_4= 8'h0E ;
parameter ROW1_5= 8'h0A ;
parameter ROW1_6= 8'h0B ;
parameter ROW1_7= 8'h09 ;
parameter ROW1_8= 8'h08 ;
parameter ROW1_9= 8'h18 ;
parameter ROW1_A= 8'h19 ;
parameter ROW1_B= 8'h1B ;
parameter ROW1_C= 8'h1A ;
parameter ROW1_D= 8'h1E ;
parameter ROW1_E= 8'h1F ;
parameter ROW1_F= 8'h1D ;
parameter ROW2_ADDR= 8'h1C ;
parameter ROW2_0= 8'h14 ;
parameter ROW2_1= 8'h15 ;
parameter ROW2_2= 8'h17 ;
parameter ROW2_3= 8'h16 ;
parameter ROW2_4= 8'h12 ;
parameter ROW2_5= 8'h13 ;
parameter ROW2_6= 8'h11 ;
parameter ROW2_7= 8'h10 ;
parameter ROW2_8= 8'h30 ;
parameter ROW2_9= 8'h31 ;
parameter ROW2_A= 8'h33 ;
parameter ROW2_B= 8'h32 ;
parameter ROW2_C= 8'h36 ;
parameter ROW2_D= 8'h37 ;
parameter ROW2_E= 8'h35 ;
parameter ROW2_F= 8'h34 ;
//20ms的计数器，即初始化第一步
reg [19:0] cnt_20ms ;
always @(posedge clk or negedge rst_n)begin
if(rst_n==1'b0)begin
cnt_20ms<=0;
end
else if(cnt_20ms == TIME_20MS -1)begin
cnt_20ms<=cnt_20ms;
end
else
cnt_20ms<=cnt_20ms + 1 ;
end
wire delay_done = (cnt_20ms==TIME_20MS-1)? 1'b1 : 1'b0 ;
//----------------------------------------------------------------------
//500ns 这里是分频，因为LCD1602的工作频率是500HZ,而FPGA是50Mhz,所以要分频
reg [19:0] cnt_500hz;
always @(posedge clk or negedge rst_n)begin
if(rst_n==1'b0)begin
cnt_500hz <= 0;
end
else if(delay_done==1)begin
if(cnt_500hz== TIME_500HZ - 1)
cnt_500hz<=0;
else
cnt_500hz<=cnt_500hz + 1 ;
end
else
cnt_500hz<=0;
end
assign lcd_en = (cnt_500hz>(TIME_500HZ-1)/2)? 1'b0 : 1'b1; //下降沿
assign write_flag = (cnt_500hz==TIME_500HZ - 1) ? 1'b1 : 1'b0 ;
//set_function ,display off ，display clear ,entry mode set
//----------------------------------------------------------------------状态机
always @(posedge clk or negedge rst_n)begin
if(rst_n==1'b0)begin
c_state <= IDLE ;
end
else if(write_flag==1) begin
c_state<= n_state ;
end
else
c_state<=c_state ;
end
always @(*)begin
case (c_state)
IDLE: n_state = SET_FUNCTION ;
SET_FUNCTION: n_state = DISP_OFF ;
DISP_OFF: n_state = DISP_CLEAR ;
DISP_CLEAR: n_state = ENTRY_MODE ;
ENTRY_MODE: n_state = DISP_ON ;
DISP_ON : n_state = ROW1_ADDR ;
ROW1_ADDR: n_state = ROW1_0 ;
ROW1_0: n_state = ROW1_1 ;
ROW1_1: n_state = ROW1_2 ;
ROW1_2: n_state = ROW1_3 ;
ROW1_3: n_state = ROW1_4 ;
ROW1_4: n_state = ROW1_5 ;
ROW1_5: n_state = ROW1_6 ;
ROW1_6: n_state = ROW1_7 ;
ROW1_7: n_state = ROW1_8 ;
ROW1_8: n_state = ROW1_9 ;
ROW1_9: n_state = ROW1_A ;
ROW1_A: n_state = ROW1_B ;
ROW1_B: n_state = ROW1_C ;
ROW1_C: n_state = ROW1_D ;
ROW1_D: n_state = ROW1_E ;
ROW1_E: n_state = ROW1_F ;
ROW1_F: n_state = ROW2_ADDR ;
ROW2_ADDR: n_state = ROW2_0 ;
ROW2_0: n_state = ROW2_1 ;
ROW2_1: n_state = ROW2_2 ;
ROW2_2: n_state = ROW2_3 ;
ROW2_3: n_state = ROW2_4 ;
ROW2_4: n_state = ROW2_5 ;
ROW2_5: n_state = ROW2_6 ;
ROW2_6: n_state = ROW2_7 ;
ROW2_7: n_state = ROW2_8 ;
ROW2_8: n_state = ROW2_9 ;
ROW2_9: n_state = ROW2_A ;
ROW2_A: n_state = ROW2_B ;
ROW2_B: n_state = ROW2_C ;
ROW2_C: n_state = ROW2_D ;
ROW2_D: n_state = ROW2_E ;
ROW2_E: n_state = ROW2_F ;
ROW2_F: n_state = ROW1_ADDR ;
default: n_state = n_state ;
endcase
end
assign lcd_rw = 0;
always @(posedge clk or negedge rst_n)begin
if(rst_n==1'b0)begin
lcd_rs <= 0 ; //order or data 0: order 1:data
end
else if(write_flag == 1)begin
if((n_state==SET_FUNCTION)||(n_state==DISP_OFF)||
(n_state==DISP_CLEAR)||(n_state==ENTRY_MODE)||
(n_state==DISP_ON ) ||(n_state==ROW1_ADDR)||
(n_state==ROW2_ADDR))begin
lcd_rs<=0 ;
end
else begin
lcd_rs<= 1;
end
end
else begin
lcd_rs<=lcd_rs;
end
end
always @(posedge clk or negedge rst_n)begin
if(rst_n==1'b0)begin
lcd_data<=0 ;
end
else if(write_flag)begin
case(n_state)
IDLE: lcd_data <= 8'hxx;
SET_FUNCTION: lcd_data <= 8'h38; //2*16 5*8 8位数据
DISP_OFF: lcd_data <= 8'h08;
DISP_CLEAR: lcd_data <= 8'h01;
ENTRY_MODE: lcd_data <= 8'h06;
DISP_ON : lcd_data <= 8'h0c; //显示功能开，没有光标，且不闪烁，
ROW1_ADDR: lcd_data <= 8'h80; //00+80
ROW1_0: lcd_data <= row_1 [127:120];
ROW1_1: lcd_data <= row_1 [119:112];
ROW1_2: lcd_data <= row_1 [111:104];
ROW1_3: lcd_data <= row_1 [103: 96];
ROW1_4: lcd_data <= row_1 [ 95: 88];
ROW1_5: lcd_data <= row_1 [ 87: 80];
ROW1_6: lcd_data <= row_1 [ 79: 72];
ROW1_7: lcd_data <= row_1 [ 71: 64];
ROW1_8: lcd_data <= row_1 [ 63: 56];
ROW1_9: lcd_data <= row_1 [ 55: 48];
ROW1_A: lcd_data <= row_1 [ 47: 40];
ROW1_B: lcd_data <= row_1 [ 39: 32];
ROW1_C: lcd_data <= row_1 [ 31: 24];
ROW1_D: lcd_data <= row_1 [ 23: 16];
ROW1_E: lcd_data <= row_1 [ 15: 8];
ROW1_F: lcd_data <= row_1 [ 7: 0];
ROW2_ADDR: lcd_data <= 8'hc0; //40+80
ROW2_0: lcd_data <= row_2 [127:120];
ROW2_1: lcd_data <= row_2 [119:112];
ROW2_2: lcd_data <= row_2 [111:104];
ROW2_3: lcd_data <= row_2 [103: 96];
ROW2_4: lcd_data <= row_2 [ 95: 88];
ROW2_5: lcd_data <= row_2 [ 87: 80];
ROW2_6: lcd_data <= row_2 [ 79: 72];
ROW2_7: lcd_data <= row_2 [ 71: 64];
ROW2_8: lcd_data <= row_2 [ 63: 56];
ROW2_9: lcd_data <= row_2 [ 55: 48];
ROW2_A: lcd_data <= row_2 [ 47: 40];
ROW2_B: lcd_data <= row_2 [ 39: 32];
ROW2_C: lcd_data <= row_2 [ 31: 24];
ROW2_D: lcd_data <= row_2 [ 23: 16];
ROW2_E: lcd_data <= row_2 [ 15: 8];
ROW2_F: lcd_data <= row_2 [ 7: 0];
endcase
end
else
lcd_data<=lcd_data ;
end
endmodule
3、testbench
`timescale 1 ns/1 ns module lcd1602_tb(); //时钟和复位 reg clk ; reg rst_n; wire lcd_en ; wire lcd_rs ; wire lcd_rw ; wire [7:0] lcd_data; //时钟周期，单位为ns，可在此修改时钟周期。 parameter CYCLE = 20; //复位时间，此时表示复位3个时钟周期的时间。 parameter RST_TIME = 3 ; //待测试的模块例化 lcd_1602_driver u1_lcd_1602_driver( .clk (clk ), .rst_n (rst_n ), .lcd_en (lcd_en ), .lcd_rw (lcd_rw ), .lcd_rs (lcd_rs ), .lcd_data(lcd_data) ); //生成本地时钟50M initial begin clk = 0; forever #(CYCLE/2) clk=~clk; end //产生复位信号 initial begin rst_n = 1; #2; rst_n = 0; #(CYCLE*RST_TIME); rst_n = 1; end endmodule
4、modesim 仿真
5、结果展示及总结
易错之处：1、忽略了lcd1602的正常工作频率
2、显示地址需要加80
3、这篇文章只是lcd1602的基本显示，下一目标就是要自定义汉字，会用到CGRAM的相关知识，详情请见下篇文章，链接如下
http://www.cnblogs.com/aslmer/p/5819868.html，欢迎提问并给出宝贵意见
转载请注明出处：http://www.cnblogs.com/aslmer/p/5819422.html
转载请注明出处：来源：oschina
链接：https://my.oschina.net/u/2963604/blog/4282545