?? i2c.v
字號:
/*
I2C總線是一種非常常用的串行總線，它操作簡便，占用接口少。本程序介紹操作一個I2C總線接口的EEPROM AT24C08
的方法，使用戶了解I2C總線協議和讀寫方法。
實驗過程是：按一下實驗板上的KEY1鍵，計數器加1計算，并把計算結果寫入EEPROM，并同時顯示在數碼管最低位，
按KEY2把EEPROM的數據讀取出來，并顯示在數碼管上。
說明：由于按鍵存在抖動,內部計數器的值偶爾可能與寫入到EEPROM的值不相同，
程序剛啟動時請先長按reset按鍵大約1秒左右，以進行初始化。
為了更好的理解程序，用戶應該仔細閱I2C總線時序規范以及AT24C08數據手冊
*/
module i2c(clk,rst,data_in,scl,sda,wr_input,rd_input,en,seg_data);
input clk,rst;
output scl; //I2C時鐘線
inout sda; //I2C數據線
input[3:0] data_in; //撥碼開關輸入想寫入EEPROM的數據
input wr_input; //要求寫的輸入
input rd_input; //要求讀的輸入
output[1:0] en; //數碼管使能
output[7:0] seg_data; //數碼管段數據
wire wr_input;
wire rd_input;
reg[7:0] seg_data;
reg scl;
reg[1:0] en;
reg[7:0] seg_data_buf;
reg[11:0] cnt_scan;
reg sda_buf;//sda輸入輸出數據緩存
reg link; //sda輸出標志
reg phase0,phase1,phase2,phase3;//一個scl時鐘周期的四個相位階段，將一個scl周期分為4段
//phase0對應scl的上升沿時刻，phase2對應scl的下降沿時刻，phase1對應從scl高電平的中間時刻，phase2對應從scl低電平的中間時刻，
reg[7:0] clk_div;//分頻計數器
reg[1:0] main_state;
reg[2:0] i2c_state; //對i2c操作的狀態
reg[3:0] inner_state;//i2c每一操作階段內部狀態
reg[19:0] cnt_delay; //按鍵延時計數器
reg start_delaycnt; //按鍵延時開始
reg[7:0] writeData_reg,readData_reg;//要寫的數據的寄存器和讀回數據的寄存器
reg[7:0] addr; //被操作的EEPROM字節的地址
parameter div_parameter=125;// 分頻系數，AT24C02最大支持400K時鐘速率
parameter start=4'b0000, //開始
first=4'b0001, //第1位
second=4'b0010, //第2位
third=4'b0011, //第3位
fourth=4'b0100, //第4位
fifth=4'b0101, //第5位
sixth=4'b0110, //第6位
seventh=4'b0111, //第7位
eighth=4'b1000, //第8位
ack=4'b1001, //確認位
stop=4'b1010; //結束位
parameter ini=3'b000, //初始化EEPROM狀態
sendaddr=3'b001, //發送地址狀態
write_data=3'b010, //寫數據狀態
read_data=3'b011, //讀數據狀態
read_ini=6'b100; //發送讀信息狀態
assign sda=(link)? sda_buf:1'bz;
always@(posedge clk)
begin
if(!rst)
cnt_delay<=0;
else begin
if(start_delaycnt) begin
if(cnt_delay!=20'd800000)
cnt_delay<=cnt_delay+1;
else
cnt_delay<=0;
end
end
end
always@(posedge clk)
begin
if(!rst) begin
clk_div<=0;
phase0<=0;
phase1<=0;
phase2<=0;
phase3<=0;
end
else begin
if(clk_div!=div_parameter-1)
clk_div<=clk_div+1;
else
clk_div<=0;
if(phase0)
phase0<=0;
else if(clk_div==99)
phase0<=1;
if(phase1)
phase1<=0;
else if(clk_div==24)
phase1<=1;
if(phase2)
phase2<=0;
else if(clk_div==49)
phase2<=1;
if(phase3)
phase3<=0;
else if(clk_div==74)
phase3<=1;
end
end
///////////////////////////EEPROM操作部分/////////////
always@(posedge clk)
begin
if(!rst) begin
start_delaycnt<=0;
main_state<=2'b00;
i2c_state<=ini;
inner_state<=start;
scl<=1;
sda_buf<=1;
link<=0;
writeData_reg<=5;
readData_reg<=0;
addr<=10;
end
else begin
case(main_state)
2'b00: begin //等待讀寫要求
writeData_reg<=data_in;
scl<=1;
sda_buf<=1;
link<=0;
inner_state<=start;
i2c_state<=ini;
if((cnt_delay==0)&&(!wr_input||!rd_input))
start_delaycnt<=1;
else if(cnt_delay==20'd800000) begin
start_delaycnt<=0;
if(!wr_input)
main_state<=2'b01;
else if(!rd_input)
main_state<=2'b10;
end
end
2'b01: begin //向EEPROM寫入數據
if(phase0)
scl<=1;
else if(phase2)
scl<=0;
case(i2c_state)
ini: begin //初始化EEPROM
case(inner_state)
start: begin
if(phase1) begin
link<=1;
sda_buf<=0;
end
if(phase3&&link) begin
inner_state<=first;
sda_buf<=1;
link<=1;
end
end
first:
if(phase3) begin
sda_buf<=0;
link<=1;
inner_state<=second;
end
second:
if(phase3) begin
sda_buf<=1;
link<=1;
inner_state<=third;
end
third:
if(phase3) begin
sda_buf<=0;
link<=1;
inner_state<=fourth;
end
fourth:
if(phase3) begin
sda_buf<=0;
link<=1;
inner_state<=fifth;
end
fifth:
if(phase3) begin
sda_buf<=0;
link<=1;
inner_state<=sixth;
end
sixth:
if(phase3) begin
sda_buf<=0;
link<=1;
inner_state<=seventh;
end
seventh:
if(phase3) begin
sda_buf<=0;
link<=1;
inner_state<=eighth;
end
eighth:
if(phase3) begin
link<=0;
inner_state<=ack;
end
ack: begin
if(phase0)
sda_buf<=sda;
if(phase1) begin
if(sda_buf==1)
main_state<=3'b000;
end
if(phase3) begin
link<=1;
sda_buf<=addr[7];
inner_state<=first;
i2c_state<=sendaddr;
end
end
endcase
end
sendaddr: begin //送相應字節的地址
case(inner_state)
first:
if(phase3) begin
link<=1;
sda_buf<=addr[6];
inner_state<=second;
end
second:
if(phase3) begin
link<=1;
sda_buf<=addr[5];
inner_state<=third;
end
third:
if(phase3) begin
link<=1;
sda_buf<=addr[4];
inner_state<=fourth;
end
fourth:
if(phase3) begin
link<=1;
sda_buf<=addr[3];
inner_state<=fifth;
end
fifth:
if(phase3) begin
link<=1;
sda_buf<=addr[2];
inner_state<=sixth;
end
sixth:
if(phase3) begin
link<=1;
sda_buf<=addr[1];
inner_state<=seventh;
end
seventh:
if(phase3) begin
link<=1;
sda_buf<=addr[0];
inner_state<=eighth;
end
eighth:
if(phase3) begin
link<=0;
inner_state<=ack;
end
ack: begin
if(phase0)
sda_buf<=sda;
if(phase1) begin
if(sda_buf==1)
main_state<=3'b000;
end
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[7];
inner_state<=first;
i2c_state<=write_data;
end
end
endcase
end
write_data: begin //寫入數據
case(inner_state)
first:
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[6];
inner_state<=second;
end
second:
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[5];
inner_state<=third;
end
third:
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[4];
inner_state<=fourth;
end
fourth:
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[3];
inner_state<=fifth;
end
fifth:
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[2];
inner_state<=sixth;
end
sixth:
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[1];
inner_state<=seventh;
end
seventh:
if(phase3) begin
link<=1;
sda_buf<=writeData_reg[0];
inner_state<=eighth;
end
eighth:
if(phase3) begin
link<=0;
inner_state<=ack;
end
ack: begin
if(phase0)
sda_buf<=sda;
if(phase1) begin
if(sda_buf==1)
main_state<=2'b00;
end
else if(phase3) begin
link<=1;
sda_buf<=0;
inner_state<=stop;
end
end
stop: begin
if(phase1)
sda_buf<=1;
if(phase3)
main_state<=2'b00;
end
endcase
end
default:
main_state<=2'b00;
endcase
end
2'b10: begin //讀EEPROM
if(phase0)
scl<=1;
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