16经典的SPI Flash的扇区擦除flash_se功能

一设计功能

对SPI_flash进行扇区擦除，分为写指令和扇区擦除两个时序部分。

二设计知识点

我简单理解flash，第一它是掉电不丢失数据的存储器，第二它每次写入新数据前首先得擦除数据，分为扇区擦除和全擦擦。

下面讲讲我自己亲自动手设计的原创代码过程：

自己设计过程：

第一步：就先看了SPI FLASH文档，了解SPI FLAHS的原理：先有写使能信号及其时序波形，然后是扇区擦除指令和地址及时序波形，再是延时3秒回到初始状态。

第二步：自己画出所有的状态及其转移图，还是就是用线性序列机表达写使能指令的时序和扇区擦除的时序，并且把他们用EXCEL表弄出相应的时间点和信号的变化（对输出信号赋值）。做完后再弄出模块框图。

第三步：根据自己的模块框图和状态转移图，还有线性序列机的EXCEL表格，描述对应的代码。

第四步：仿真验证是否出错。

我的设计思想如下图所示，三部分。

一是计数器（写使能时序的计数器，扇区擦除的计数器，延时三秒的计数器）.

二是，状态机。（初始状态，写使能指令状态，擦除扇区的状态，延时三秒的状态）

三是，线性序列机。（由写指令和擦除扇区的时序图弄好计数值及信号变化）

计数器：

一是WF计数器，计到41，位宽为6。

 二是SE计数器，计到128.，位宽为9

 三是延时3秒的计数器， 计到150M，位宽为28

针对众多时序逻辑的编码方法：第一步在excel中，分成两列，一列是计数值（使用序列填充，等差），一列是对应的信号变化。第二步，直接在notepad++里使用列编辑加上分号，欧克勒。

线性序列机：

                

WE的时序逻辑：下图为WREN时序波形图。

时间ns

计数值

信号的操作

0

0

Begin sck<=0;cs_n<=1;sdi<=0;end

20

1

Begin sck<=0; cs_n<=0;end

80

4

sck<=1;

120

6

sck<=0;

160

8

sck<=1;

200

10

sck<=0;

240

12

sck<=1;

280

14

sck<=0;

320

16

sck<=1;

360

18

sck<=0;

400

20

sck<=1;

440

22

Begin sck<=0; sdi<=1;end

480

24

sck<=1;

520

26

Begin sck<=0; sdi<=1;end

560

28

sck<=1;

600

30

Begin sck<=0; sdi<=0;end

640

32

sck<=1;

680

34

sck<=0;

700

35

cs_n<=1;

800

40

SE的时序逻辑：下图为SE时序波形图。

 

下面为线性序列机的EXCEL描述SE时序：

时间点	计数值	信号的变化
40	2	Begin sck<=1;sdi<=1;end
80	4	sck<=0;
120	6	Begin sck<=1;sdi<=1;end
160	8	sck<=0;
200	10	Begin sck<=1;sdi<=0;end
240	12	sck<=0;
280	14	Begin sck<=1;sdi<=1;end
320	16	sck<=0;
360	18	Begin sck<=1;sdi<=1;end
400	20	sck<=0;
440	22	Begin sck<=1;sdi<=0;end
480	24	sck<=0;
520	26	sck<=1;
560	28	sck<=0;
600	30	sck<=1;
640	32	sck<=0;
680	34	Begin sck<=1;sdi<=SE_addr[23];end
720	36	sck<=0;
760	38	Begin sck<=1;sdi<=SE_addr[22];end
800	40	sck<=0;
840	42	Begin sck<=1;sdi<=SE_addr[21];end
880	44	sck<=0;
920	46	Begin sck<=1;sdi<=SE_addr[20];end
960	48	sck<=0;
1000	50	Begin sck<=1;sdi<=SE_addr[19];end
1040	52	sck<=0;
1080	54	Begin sck<=1;sdi<=SE_addr[18];end
1120	56	sck<=0;
1160	58	Begin sck<=1;sdi<=SE_addr[17];end
1200	60	sck<=0;
1240	62	Begin sck<=1;sdi<=SE_addr[16];end
1280	64	sck<=0;
1320	66	Begin sck<=1;sdi<=SE_addr[15];end
1360	68	sck<=0;
1400	70	Begin sck<=1;sdi<=SE_addr[14];end
1440	72	sck<=0;
1480	74	Begin sck<=1;sdi<=SE_addr[13];end
1520	76	sck<=0;
1560	78	Begin sck<=1;sdi<=SE_addr[12];end
1600	80	sck<=0;
1640	82	Begin sck<=1;sdi<=SE_addr[11];end
1680	84	sck<=0;
1720	86	Begin sck<=1;sdi<=SE_addr[10];end
1760	88	sck<=0;
1800	90	Begin sck<=1;sdi<=SE_addr[9];end
1840	92	sck<=0;
1880	94	Begin sck<=1;sdi<=SE_addr[8];end
1920	96	sck<=0;
1960	98	Begin sck<=1;sdi<=SE_addr[7];end
2000	100	sck<=0;
2040	102	Begin sck<=1;sdi<=SE_addr[6];end
2080	104	sck<=0;
2120	106	Begin sck<=1;sdi<=SE_addr[5];end
2160	108	sck<=0;
2200	110	Begin sck<=1;sdi<=SE_addr[4];end
2240	112	sck<=0;
2280	114	Begin sck<=1;sdi<=SE_addr[3];end
2320	116	sck<=0;
2360	118	Begin sck<=1;sdi<=SE_addr[2];end
2400	120	sck<=0;
2440	122	Begin sck<=1;sdi<=SE_addr[1];end
2480	124	sck<=0;
2520	126	Begin sck<=1;sdi<=SE_addr[0];end
2560	128	sck<=0;

二设计输入

Flash扇区擦除的功能模块

module flash_se(

input wire clk,

input wire rst_n,

input wire we_flag,

input wire [23:0]SE_addr,

output reg     sck,

output reg     sdi,

output reg     cs_n

       );

reg we_en;            //进入写使能指令时序的标志信号

reg se_en;             //进入扇区擦除指令时序的标志信号

reg [3:0]state;//定义状态变量

reg sck0,sck1;

reg sdi0,sdi1;

reg cs_n0,cs_n1;

parameter idel = 4'b0001;           //初始状态

parameter WERN = 4'b0010;             //写使能指令状态

parameter SE = 4'b0100;             //扇区擦除

parameter DELAY = 4'b1000;//3秒延时状态

reg[5:0]we_cnt;

reg[7:0]se_cnt;

reg[27:0]delay_cnt;

//写使能指令时序的计数器

always@(posedge clk or negedge rst_n)

if(!rst_n)

       we_cnt<=0;

else if(we_cnt=='d41)

       we_cnt<=0;

else if(we_en)

       we_cnt<=we_cnt+1'b1;

//扇区擦除时序的计数器

always@(posedge clk or negedge rst_n)

if(!rst_n)

       se_cnt<=0;

else if(se_cnt=='d128)

       se_cnt<=0;

else if(se_en)

       se_cnt<=se_cnt+1'b1;  

parameter T3S = 28'd150_000_000-1;

always@(posedge clk or negedge rst_n)begin

       if(rst_n==1'b0)begin

              state<=idel;

              delay_cnt<=0;

              we_en<=0;

              se_en<=0;

              end

       else begin

              case(state)

                     idel: if(we_flag)    //投入0.5元

                                   state<=WERN;

                                   else

                                   state<=idel;

                                  

                     WERN:if(we_cnt=='d41)begin

                                   state<=SE;

                                   we_en<=0;

                                   end

                            else begin

                                   state<=state;

                                   we_en<=1;

                                   end

                     SE:if(se_cnt=='d128)begin

                                   state<=DELAY;

                                   se_en<=0;

                                   end

                            else begin

                                   state<=state;

                                   se_en<=1;

                                   end

                     DELAY:if(delay_cnt==T3S)begin

                                   state<=idel;

                                   delay_cnt<=0;

                                   end

                            else begin

                                   delay_cnt<=delay_cnt+1'b1;

                                   state<=state;

                            end

                     default:state<=idel;

              endcase

       end

end

//写使能信号时序通过线性序列机

always@(posedge clk or negedge rst_n)

if(!rst_n)begin

       sck0<=0;cs_n0<=1;sdi0<=0;

end

       else begin

              case(we_cnt)

                    

0 :cs_n0<=0;

1 :sck0<=1;

4 :sck0<=0;

6 :sck0<=1;

8 :sck0<=0;

10:sck0<=1;

12:sck0<=0;

14:sck0<=1;

16:sck0<=0;

18:sck0<=1;

20:sck0<=0;

22:begin sck0<=1; sdi0<=1;end

24:sck0<=0;

26:begin sck0<=1; sdi0<=1;end

28:sck0<=0;

30:begin sck0<=1; sdi0<=0;end

32:sck0<=0;

34:sck0<=1;

35:sck0<=0;

40:begin sck0<=0;cs_n0<=1;sdi0<=0;end

              default: ;

              endcase

       end

//扇区擦除时序通过线性序列机

always@(posedge clk or negedge rst_n)

if(!rst_n)begin

       sck1<=0;cs_n1<=1;sdi1<=0;

end

       else begin

              case(se_cnt)

0:begin sck1<=0;cs_n1<=1;sdi1<=0;end          

2     :begin sck1<=1;cs_n1<=0;end

4     :sck1<=0;

6     :begin sck1<=1;sdi1<=1;end

8     :sck1<=0;

10   :begin sck1<=1;sdi1<=0;end

12   :sck1<=0;

14   :begin sck1<=1;sdi1<=1;end

16   :sck1<=0;

18   :begin sck1<=1;sdi1<=1;end

20   :sck1<=0;

22   :begin sck1<=1;sdi1<=0;end

24   :sck1<=0;

26   :sck1<=1;

28   :sck1<=0;

30   :sck1<=1;

32   :sck1<=0;

34   :begin sck1<=1;sdi1<=SE_addr[23];end

36   :sck1<=0;

38   :begin sck1<=1;sdi1<=SE_addr[22];end

40   :sck1<=0;

42   :begin sck1<=1;sdi1<=SE_addr[21];end

44   :sck1<=0;

46   :begin sck1<=1;sdi1<=SE_addr[20];end

48   :sck1<=0;

50   :begin sck1<=1;sdi1<=SE_addr[19];end

52   :sck1<=0;

54   :begin sck1<=1;sdi1<=SE_addr[18];end

56   :sck1<=0;

58   :begin sck1<=1;sdi1<=SE_addr[17];end

60   :sck1<=0;

62   :begin sck1<=1;sdi1<=SE_addr[16];end

64   :sck1<=0;

66   :begin sck1<=1;sdi1<=SE_addr[15];end

68   :sck1<=0;

70   :begin sck1<=1;sdi1<=SE_addr[14];end

72   :sck1<=0;

74   :begin sck1<=1;sdi1<=SE_addr[13];end

76   :sck1<=0;

78   :begin sck1<=1;sdi1<=SE_addr[12];end

80   :sck1<=0;

82   :begin sck1<=1;sdi1<=SE_addr[11];end

84   :sck1<=0;

86   :begin sck1<=1;sdi1<=SE_addr[10];end

88   :sck1<=0;

90   :begin sck1<=1;sdi1<=SE_addr[9];end

92   :sck1<=0;

94   :begin sck1<=1;sdi1<=SE_addr[8];end

96   :sck1<=0;

98   :begin sck1<=1;sdi1<=SE_addr[7];end

100  :sck1<=0;

102  :begin sck1<=1;sdi1<=SE_addr[6];end

104  :sck1<=0;

106  :begin sck1<=1;sdi1<=SE_addr[5];end

108  :sck1<=0;

110  :begin sck1<=1;sdi1<=SE_addr[4];end

112  :sck1<=0;

114  :begin sck1<=1;sdi1<=SE_addr[3];end

116  :sck1<=0;

118  :begin sck1<=1;sdi1<=SE_addr[2];end

120  :sck1<=0;

122  :begin sck1<=1;sdi1<=SE_addr[1];end

124  :sck1<=0;

126  :begin sck1<=1;sdi1<=SE_addr[0];end

128  :begin sck1<=0;cs_n1<=1;sdi1<=0;end

              default: ;

              endcase

       end 

       //对于输出避免冒险通过选择器

       always@(posedge clk or negedge rst_n)

       if(!rst_n)

       begin

              sck<=0;cs_n<=1;sdi<=0;

       end

       else if(state==WERN)begin

              sck<=sck0;cs_n<=cs_n0;sdi<=sdi0;

end

       else if(state==SE)begin

              sck<=sck1;cs_n<=cs_n1;sdi<=sdi1;

end

endmodule

Flash扇区擦除的测试模块

`timescale 1ns/1ns

`define clk_period 20

module flash_se_tb;

reg   clk   ;

reg   rst_n ;

reg   we_fla;

reg[23:0]SE_add;

wire  sck   ;

wire  sdi   ;

wire  cs_n  ;

initial clk =1;

always#10 clk =~clk;

initial begin

       rst_n =0;

       we_fla =0;

       SE_add = 0;

       #(`clk_period*2);

       rst_n =1;

       we_fla =1;

       SE_add = 24'b0100_0010_0000_0000_0000_0000;

       #(`clk_period);we_fla =0;

       #(`clk_period*400);

       rst_n =0;

#(`clk_period*20);

$stop;

end

       flash_se #(.T3S(199)) inst_flash_se (

                     .clk     (clk),

                     .rst_n   (rst_n),

                     .we_flag (we_fla),

                     .SE_addr (SE_add),

                     .sck     (sck),

                     .sdi     (sdi),

                     .cs_n    (cs_n)

              );

endmodule

三FLASH的扇区擦除的仿真波形如下

我的收获是：

首先是第一次遇到陌生有难度的东西，不要怂，要静下心来亲自动手做和思考，一步步的。

其次是，弄懂设计原理和设计思路，这可能占了整个设计的40%，调试代码占了40%，敲代码只占了10%，还有10%就是记录整理勒。画好图纸比敲代码重要得多，代码只不过是思路的描述。